One of the most remarkable stereoscopes ever produced commercially was the Ives Kromskop (Patent #531,040, Dec 18, 1894). In it, three stereoscopic glass positives made from negatives exposed through red, green, and blue filters are optically superimposed to give a full color image of remarkable quality. It was more than ten years prior to the introduction of relatively crude full color plates such as the Autochrome.

This viewer and a complementary one-shot color camera were inspired by Frederic Eugene Ives (1856–1937), a pioneer in the field of halftone printing where he held many important patents. The reproduction of nature in full color was his other absorbing interest. It occupied so much of his time that he founded a company at 1324 Chestnut Street in Philadelphia that remained in business over forty years even though mass acceptance of any of his ideas never came to pass. A New York showroom was also established at 18W. 33rd St.

Early attempts

In 1861, James Maxwell, the British Physicist, showed that by projecting superimposed red, green, and blue images, a full color image could be produced. Lack of color sensitive (panchromatic) film in those days was a serious drawback, and some thirty years passed before the emulsions existed which Ives used in making his color separations.

Ives’ first color patent #672,573 (July22,1890) described the basic three color (additive)process and the use of three positive images in a special triple lantern to produce a full color image on the screen (Fig. 1). He also covered the use of negatives in the production of printed color images using the halftone process. The printing colors then become cyan, magenta and yellow, the complementary (subtractive) colors for red, green, and blue. Announcement of his achievement led to an invitation to England in 1892 which lasted for two full years as he “captured crowded audiences at a series of lectures:’

He returned to America in April 1894 and set about putting his ideas into commercial form. This led to the invention of a viewing device first known as the Photochromscope. He was back in England little more than a year later both to promote his halftone process and to introduce the perfected viewer now named the Kromskop. In 1896, the British Kromskop Syndicate was formed to exploit this invention, but it was never successful and the project was terminated in 1898 when Ives returned to Philadelphia. His long sojourn and great promotional activity in England and on the Continent help to explain the relative abundance of these rare viewers on the overseas market.

The real challenge was to find a practical way for optically combining six images to produce a color stereo image. The first images were made on a single glass plate, side by side to fit conveniently in the triple lantern projector. The same three images in the original Ives Photochromscope viewer, although only monocular, required seven reflectors, six lenses, plus the three color screens. The stereo Kromskop finally reached the market with only two tinted transparent mirrors, an external reflector for distribution of illumination, two additional color filters, and the viewing lenses.

The problem had been tackled by other inventors without success. In Fig. 2 a simple arrangement dating back at least twenty years is shown, using a mirror C and two plain glass reflectors A and 8. The three separations are placed ahead of the appropriate color filters and the distance from the viewing lens is constant. There are two basic problems. The optical path is too long, making the picture very small. Also, the glass mirrors, which both transmit and reflect, create annoying double images.

Final form

Ives’ ingenious solution is diagramed in Fig. 3. The original mirror C is eliminated to shorten the optical path. A green transmitting reflector is used for the blue image, and blue for the red image. The green reflector also serves as the color filter for that image. When the red or blue images are reflected from these tinted mirrors, the annoying secondary image that normally bounces off the back side of the glass is absorbed by the complementary color in the glass.

Initial alignment of the viewer is accomplished by the angle and squareness of the two transmitting reflectors shown in Fig. 4. The glasses are spring loaded against rotatable triangular stops to allow a small change in inclination. Through this adjustment, the red or blue images can be raised or lowered independently with respect to the green. The base support for the mirrors can be rotated for initial horizontal alignment. These are normally factory adjustments, but they sometimes have been tampered with and it is not easy to bring back proper alignment. In the early versions, these adjustments were crude. Later versions have threaded verniers that are a great help if things are truly out of line.

The block on which the reflectors are mounted fits slidably into the instrument, coming to rest against a small eccentric wheel. Turning a knob on the outside of the viewer moves the assembly back and forth a small amount. This simultaneously raises and lowers the red and blue images to line them up with the green. In a later design, a threaded screw at the right front of the viewer provides the same function in a more positive manner.

Commercial product

The commercial product, (Patent #531,040, Dec. 18, 1894) is illustrated in Fig. 5. It is a precision device of polished mahogany and brass most likely made in England with final assembly and calibration in Philadelphia. When properly aligned and illuminated, the results are quite spectacular. Superimposing six 2″ by 2″ quality images virtually eliminates grain. The three pairs are precision mounted in masks and held loosely together by silk tapes and are fan-folded for storage (Fig. 6). The positive green image slips into a slot at the rear and is non-adjustable. The blue image lies horizontally on the first step in two-point contact with a factory aligned brass plate. Only a very small horizontal adjustment is possible. The red image mounts similarly at the top, with the addition of a vernier screw at the left for precise horizontal adjustment only. The spacer card between the red and blue images bears the title.

A complete Kromogram unfolded on a light box with the left images filtered to show the color which would be provided and combined by a Kromskop viewer. Except for the green, the images are inverted and reversed for viewing in the transmitting reflectors shown in figure 4. Kromogram windows are exactly 2″ wide with a three-sixteenth inch septum and only 55mm center to center. The mounts are 5.25″ wide.

Notes on use

In use, the viewer is always tipped up to improve illumination, to ensure that the red and blue images lie against the stops, and to make the vernier on the reflectors operate properly.

Proper illumination is most important. A daylight diffuser (Fig. 7) was standard equipment, but it is generally missing. It was of opal glass, mahogany edged, and rested on the two pins at the back of the reflector. A chain permits it to be swung to the rear for changing slides. Ground glass is not a suitable substitute. Normal illumination was by skylight. At night the “Kromskop Night Illuminator” was available for $12 (Fig.8). Two Welsbach gas burners were used and the exterior housing was of polished mahogany and brass.

The reflector at the rear of the viewer sends light through the “green” image. In some instruments, the mirror is tinted green, but it can be a more neutral color such as yellow since the true spectral filter is a transparent mirror inside the viewer. By sliding out the block containing the mirrors, the viewer becomes an ordinary stereoscope for viewing specially mounted glass stereograms or for looking at the “green” image as a black and white positive.

The design just described introduces a small error in registration due to the fact that the green image passes through two slanted transparent mirrors which slightly compress the image vertically. The blue image passes through just one. In compensation, a plain glass (double the thickness of the mirrors) is placed at the same angle just below the “red” image (Fig. 3). This brings the important red and green images into correct register, leaving a small error in the blue which in practice is not noticeable.

Taking pictures

The pictures were generally taken on a single glass plate. For still lifes, a multiple back was sold to use vertically split 5″ by 7″ plates (Fig. 9). A stereo version of this back was also produced using the full plate. Positives made by contact printing were reversed right to left unless a reversing mirror of prism was fitted in the lenses. Glass plates, mounting frames and other supplies plus a mounting service were available. The positives are ready for cutting and mounting directly on the Kromogram frames, but nothing is said about the requirement for great accuracy. Register is on the same order as that used today for lap dissolve pairs.

For instantaneous photographs an ingenious “one shot” camera was produced. In the diagram (Fig. 10) the prisms F and G are placed so that their inner front edges partially cover a rectangular aperture in the lens system. The double internal reflection leaves the two images unreversed, and the greater refractive index of the glass compensates for the longer light path. The camera required exposures on the order of five to ten seconds in bright sunlight. It was priced at $75 with the stereo version projected at something less than double that price. In making single views for the lantern Kromskop, the camera was used in the horizontal position. The later stereo version pared the cameras vertically, allowing a “normal” lens separation.

Available picture series

The Kromskop came with eight Kromograms for $50. A large selection of Kromograms was available, the “A” Series priced at $1 ($10 per dozen) and the “B” Series at $1.50 ($15 per dozen). One 12-page price list covers almost 400 subjects.

While perhaps not a major factor in the failure to achieve commercial success, the pictures as a whole are disappointing. Exposure, general print quality, and color rendition are excellent, but the photography was by people with little or no understanding of good stereo composition.

Outdoor scenes were particularly poor. A group of people including Ives visited Paris in 1897–98 proceeding on to Switzerland, and about three dozen views were published as a result. Scarcely one has a foreground object within 100 feet of the camera, and the need for near perfect registration makes them generally disappointing in the viewer. Even more remarkable was the promotion of upwards of 100stereo pictures of paintings from the National Gallery in London! Still lifes were casually set up with little regard for esthetics. Some thought was given to choosing subjects that demonstrated nuances in color. Some of the flower arrangements are very good, primarily because of the excellent color reproduction.

A special set of medical views was produced in the hope that the medical profession would recognize the great benefits of full color 3‑D. Views were offered from Paris, London, Philadelphia, Niagara Falls and Washington DC. A series of still life subjects and a small number of portraits were an important part of the listings. A portrait of Mrs. McKinley in the White House Conservatory was taken at the same time as the widely distributed Underwood and Underwood view card.

Conclusion

In summary – if you own a Kromskop and have some fine examples to show, treat them with care and be chary about acquiring additional ones which may be mediocre examples from the published lists or even poorer amateur efforts.

No information is available on the number of views produced. Design variations suggest that several small production runs were made, with sales of the last units spread out over a number of years.

Proper illumination and register of the views was a serious drawback. The expense and relatively poor quality of the commercial views must have been a factor. Making Kromograms demanded more skill than the average amateur could give to it. It all added up to failure in spite of the enthusiasm of the professional critics.

At least one competitive system appeared briefly around 1900.It was known as the “Kromaz”. A single lens camera using mirrors made two exposures, and the resulting four images, one red, two green and one blue were optically combined in a viewer.

In the meantime, other inventors, notably the Lumière brothers, were working towards direct color transparencies based on the additive color process. In 1907they began marketing Autochrome plates (including stereo sizes), the first commercially successful color process. It wasn’t until 1935that the superior subtractive color process to be known as Kodachrome virtually put an end to efforts using the familiar red, green, and blue filters.

The Kromskop is seldom mentioned today. Relatively few people have had the opportunity to see properly illuminated views in a Kromskop. These reproductions are the first ever done in 3‑D. They are a reminder of the tremendous achievement of this great inventor.

The author wishes to thank George Eastman House and the International Museum of Photography in Rochester, NY for their help with images and information in this article.

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Paul Wing (Hingham, Massachusetts, USA)

Paul Wing was born in Sandwich, Massachusetts on March 9, 1913. Paul was first intrigued with stereocards in the early 1920s and by the time he finished high school during the Great Depression he was making “cha cha,” stereo photographs using side-step with a [2D] Kodak Brownie camera. In the 1940s, Paul met Dr. Philip Batchelder, a stereo collector and a member of the American Branch of the Stereoscopic Society of Great Britain. “It opened a New World,” Paul wrote in the foreword to his book on stereoscopes.
The importance of Paul Wing in contemporary stereography cannot be overstated. Paul was a veteran of more than a half century of stereoscopy and was one of only four Lifetime Members in the Stereoscopic Society of America (SSA). Member number 385 in the SSA, Paul was an internationally recognized master stereographer and the author of “Stereoscopes: The First One Hundred Years,” (Transition Publishing: 1996), the definitive history on the subject and one which will undoubtedly remain so for a long time to come.
He passed away on March 7, 2002 two days before his 89th birthday.

Full text: 3D Legends

Notes by Pascal Martiné: This article was first published 35 years ago. It is thanks to David Starkman’s presentation for the Virtual Stereoscopic Community that this article is now available to a wider audience. Transferring a print layout to a digital medium requires to pay attention to multiple aspects. That’s why I have allowed myself to re-arrange the pictures within the text and to optimize the graphics. Therefore, I replaced some pictures with newly taken digital photos of my own Kromskop, optimized all graphics and gently sharpened the pictures of Paul Wing’s Kromograms (without changing the color appearance). Finally, because it has become common practice with blog posts, I added subheadings.

Der Beitrag The Ives Kromskop erschien zuerst auf the stereosite.

Introduction

In life, most humans see the world from two distinct viewpoints: one from each eye.  The left eye receives an image slightly different from the right eye because it is focusing on the object of interest from a slightly different angle.  The brain uses these differences to perceive depth.

The term ‘Stereoscopy’ refers to what is now more widely known as 3D imaging, i.e., recording and presenting visual information in three dimensions.  When a stereoscopic image is viewed properly, the brain perceives depth as it would in the physical world.  Thus, a flat paper or screen can carry spatial information. This simple concept can be adapted into drawing, photography and video for true 3D visualization. 

Charles Wheatstone discovered the concept of stereoscopy and built the first viewing devices in 1832¹.  By 1852 the Brewster-type stereoscope was publicly available¹.  This handheld device allowed the common individual to view side-by-side (SBS) stereophotography formats and helped incite the great popularity of stereoscopy in the mid 19th century¹.  Though this popularity increased and decreased throughout the decades, the concept was continuously applied to a variety of practices including art, film, photography, history, and medicine. 

In the present day a variety of viewing devices exist.  Polarized light projection and filtered glasses allow both left and right eye images from one screen.  It is currently widely used, and known to the general public via 3D movies.  SBS stereo images can also be “free-viewed” by those individuals who have trained their eyes to diverge on the page: each eye focused on its corresponding image.  This easy access allows the visualization of true 3D depth, as it is naturally perceived by the brain, for a variety of purposes without the need for advanced or expensive technologies.

Stereoscopy in Medical Education

The use of stereoscopy for medical education began in the early 20th century.  Some sources indicate that Dr. Daniel John Cunningham was the first to use SBS stereographs to teach human anatomy^2,3.  In 1909 his work was compiled into several volumes of Stereoscopic Studies of Anatomy, eventually comprising the Edinburgh Stereoscopic Atlas of Anatomy^3,4.  By the mid-century mark, a resurgence in the popularity of stereoscopic viewing sparked collaboration between anatomist Dr. David L. Bassett and William B. Gruber, inventor of the Viewmaster system.  They created a collection of stereoscopic disks featuring dissections by Bassett and photographs by Gruber: A Stereoscopic Atlas of Human Anatomy⁴.

Stereoscopic anatomical teaching continues to be of use today.  The retention of knowledge in medical student groups shown 3D stereoscopic videos is greater than that of groups shown 2D videos^2,6.  This result is significant in anatomical relationships, while functional knowledge appears unaffected².  The strength of this learning impact is still unknown.  Some studies determined no significant difference in written test scores between 3D and 2D video learning⁷.  These inconclusive results are potentially due to the type (ie. functional verses spatial) of questions tested.  The benefit of 3D learning varies from person to person.  A large predictor of a student’s success in anatomic learning is visuospatial ability; stereoscopic learning aids may be more beneficial for those with lower natural visuospatial scores^6,7,8.  It effectively evens the playing field.  Unfortunately, though many medical schools currently give students access to 3D computer models, they are displayed or projected onto flat screens, and thus lose the actual stereoscopic benefit^6,8.  Modern teaching programs with true stereoscopic projection of CT vascular models have been introduced through polarized projection^7,9.  When introduced to stereoscopic techniques of learning, students find it useful and are interested in using it in the future^6,10.

Figure 1: Stereoscopic teaching tools throughout the decades (1905–1960).

In the 21st century, stereoscopic teaching has been thoroughly modernized and adapted, significantly in the field of neurosurgery, where many practice-hours are needed despite limited availability of patients and OR time¹⁰.  Virtual reality (VR) simulations in 3D space allow residents to gain experience in the field without risk to patients¹⁰.  These can be both haptic (touch simulation) and non-haptic, and studies have shown them to be significantly beneficial compared to control groups without VR, though some uncertainty exists^11,12,13.  The hepatic portion of the simulation training may not contribute significantly to the benefit, suggesting that the improved learning outcomes is due to the stereoscopic VR¹³.  Stereoscopic models are also used for learning purposes in other specialities¹⁰.

Stereoscopy in Surgery

Stereoscopic techniques in surgery are not simply limited to training and simulation.  As early as 1922, surgeons had adapted the knowledge of stereopsis for use in the OR¹⁵.  Gunnar Holmgren retained depth when magnification was required by first using binocular microscopes at the University Clinic of Stockholm¹⁵.  This technique was quickly employed worldwide and had especial benefit in the small surgeries of the head and neck¹⁵.

Stereoscopy is also a useful phenomenon in laparoscopic surgeries.  Traditionally, the laparoscope video is displayed on a 2D monitor and therefore lacks potentially crucial depth information.  Stereoscopic laparoscopes allow true 3D relationships to be determined without opening the body cavity to human eyes¹⁶.  This is done simply by including two visual viewpoints and then viewing them via any stereoscopic method.  As minimally invasive surgeries, and therefore laparoscopy, increased in complexity, the difficulties of performing procedures without depth became apparent¹⁷.  In the early 1990s stereoscopic laparoscopy was used for the first time on human patients: a laparoscopic cholecystectomy performed at Nuclear Research Center Karlsruhe¹⁷.  The incorporation of stereoscopy in laparoscopic procedures increases the ease of tasks that require 3D visualization such as organ mobilization and suturing¹⁷.  A 2017 literature review by Schwab et al. collected objective and subjective information from patients and surgeons using 2D vs 3D laparoscopic systems during cholecystectomy operations¹⁸.  They found that there were no increased negative outcomes in either method, and that many surgeons perceived better depth perception and control with the 3D systems¹⁸.  Stereoscopic laparoscopy can also be combined with laparoscopic ultrasound for augmented reality views of internal structures¹⁶. 

Image-guided surgery (IGS) is widely used in a variety of fields¹⁴.  IGS allows a 3D surgical plan to be developed on a 3D model of the patient which is created from preoperative imaging¹⁴.  3D models are also used for pre-planning, head frame placement and to determine accessibility before radiosurgery¹⁹.  This shortens procedure times, optimizes patient experience and decreases repeat procedures¹⁹.  Unfortunately, most of these models are viewed on a 2D monitor, eliminating the benefit of true stereoscopic effect¹⁴.  It would be beneficial and feasible to include stereoscopic viewing through a polarized display¹⁴.

3D imaging can be performed intraoperatively within the OR through stereoscopic recording and polarization¹⁴.  These images may be combined with the preoperative models for intraoperative visualization¹⁴.  The ease of incorporating stereoscopy into surgery increases as technology develops.  Something as commonly available as a smartphone can be adapted into a viewing device²⁰.  Successful robot-assisted ophthalmic surgery simulations have been performed by attaching a stereoscopic camera to a binocular surgical microscope and displaying the resultant image on a smartphone VR headset²⁰.

High-definition stereoscopic 3D imaging in real-time is crucial in the emerging field of telesurgery.  With ultra-fast 5G internet connection it is possible to perform robot-assisted laparoscopic surgeries thousands of kilometres from the patient site^21,22.  These methods, though still new, could potentially combat surgeon shortages, remote access problems, and disease spread²¹.

Figure 2: An example of telesurgery technologies.

Stereoscopy in Ophthalmology

Stereoscopy is an important part of vision.  Screening and testing for stereoscopic acuity can help diagnose a variety of ocular conditions including strabismus and amblyopia²³.  There are several stereoscopic tests ranging in specificity and ease of use for the appropriate patient case and physician concern. 

In 1960 Bela Julesz used random-dot stereocards to test for stereoscopic acuity²³.  These random patterns of dots appear flat and uninteresting when viewed monocularly, but when the test subject uses intact binocular vision through a stereoscopic viewing device, shapes emerge in the depth²³.  The TNO stereotest utilizes the same concept and tests mostly for amblyopia²³.  It is viewed in red/blue anaglyph and consists of recognisable images instead of depth clues²³.  TNO tests are designed so that when viewing monocularly, an incorrect image is still visible²³.  A quantitative aspect is also added²³.  The Lang test is similar again, but uses a panographic viewing technique where no special glasses are required²³.  The most common stereotest is the Titmus test, in which raised shapes and objects are detected when viewed through polarized glasses²³.

Lang’s two pencil test, first described in 1983, removes the need for any specialized stereodevice²⁴.  It requires that the patient correctly line up a pencil with one held by the examiner; binocular performance is compared against monocular in each eye^23,24,25.  This is a qualitative test and is not used for diagnosis, but has been shown to distinguish gross strabismus at a high sensitivity and specificity compared to random-dot and TNO with a negative predictive value of 100%²⁵.

Figure 3: Stereoscopic acuity tests.

Stereoscopy is not only used to test for ocular conditions; it’s also used to treat them.  Non-surgical treatments of eye movement and ocular muscle disorders such as strabismus are known as orthoptics: these include stereoscopic exercises.  Dr. Louis Javal introduced orthoptic treatment for strabismus in the late 19^th century, using early Wheatstone stereoscopes to induce proper binocular focus²⁶.  The binocular training provided by these treatments is used in replacement of and to support surgery²⁶.  The over-reliance and misuse of early orthoptics damaged their therapeutic reputation around the turn of the century, but treatments were modernized in 1919 by doctors E. E. and M. C. Maddox and eventually re-popularized their use²⁶.  M. C. Maddox created stereocards for the amblyoscope (later the synoptophore), a reflecting stereoscope-like device that allows for individual eye stimulation with lights, divergence angle measurement, and determination of the area of suppression²⁷.

In 1927 Dr. Carl Sattler published the first set of orthoptic stereocards for strabismus diagnosis and treatment that were available for use at home²⁸.  They were inexpensive and available for parents to purchase for their children²⁸.  Other similar sets were soon available and widely used until the 1950s²⁸.

Figure 4: Orthoptic stereocards for strabismus diagnosis and treatment.

The benefit of orthoptic exercises continues to be of controversy today.  Ophthalmologists dispute whether lengthy exercises support marked therapeutic improvement²⁶.  Studies have shown that stereoscopic orthoptic training for only two weeks (15 mins twice a day) mildly increases the angle of fusion in strabismus patients and decreases the required prismatic correction²⁹.  Longer training can lead to greater improvement and the remission of tropia²⁹.  These benefits depend on the individual’s motivation, time commitment, and the nature of their presenting strabismus^29,30.  Exodeviation seems to benefit more than esodeviation, while vertical deviation shows no effect²⁹.  The outcome of orthoptic training depends largely on the severity of strabismus prior to starting therapy: better results correlate with milder cases³⁰.  Non-surgical treatments are therefore reserved for mild or small angle strabismus^26,29,30.  They cannot overcome large disparities that would benefit from surgery²⁶.  These inherent limitations of orthoptics are often misunderstood, leading to misapplication of orthoptic therapies, poor outcomes and decreased clinical support²⁶.

Stereoscopy can also be used in screening for glaucoma³¹.  Ocular fundus images are often analyzed for diagnostic characteristics of the optic nerve head; this is especially true for normotensive glaucoma that cannot be detected with a tonometer³¹.  Important features such as the cup depth, disc shape and cup to disc ratio are used in screening^31,32.  Correct diagnosis of glaucoma based on these features is aided by stereoscopic analysis^31,32,33,34.  Ophthalmologists can view these stereoscopic images either digitally or on film³³.  When comparing glaucoma detection using stereoscopic versus monoscopic images, the stereoscopic screening detects cases at increased sensitivity and reproducability³².  Stereoscopic images more accurately indicate glaucoma patients that are nearer the cup to disc ratio threshold³².  Furthermore, computer-aided machine-learning detection methods that focus on analyzing stereoscopic images of the ocular fundus outperform those that rely only on a single image with no depth information^31,34.

Conclusion

This is by no means a comprehensive collection of the uses of stereoscopy in medicine.  The increased information of 3D contributes benefits to many areas of imaging not mentioned above, such as screening mammography, echocardiography, bronchoscopy and scintigraphy^35,36,37,38.  Humans exist in and process the physical world in three dimensions; it is no surprise that the best medical observations also include depth information. 

Stereoscopy remains a long-studied and under-used technology in medicine.  It is used widely in some specialities, including anatomy, neurosurgery, laparoscopic surgery, imaging and ophthalmology, but remains a relatively unknown concept in the general medical and non-medical population.  Common criticisms of stereoscopy in all fields include the need for additional viewing devices, glasses or tools^10,23,32.  While this is potentially true, novel and inexpensive stereoscopic devices are available in the majority of cases^20,28.

The popularity of stereoscopy has ebbed and flowed over the many decades since Charles Wheatstone first described its principle¹.  The extent of its use in medicine has followed a similar process.  The current progress in computer technology allows for increased consumption of modern 3D movies, and increased innovation in the medical field.  We exist in a current stereoscopic boom.  There are more opportunities for stereoscopy in virtual care and remote procedures^21,22.  More 3D tools are available to medical students^6,8.  For recorded depth information to be of benefit, 3D data need to be viewed not from flat screens, but from stereoscopic viewers.  Only in this way is the patient truly represented.

References

1. Pellerin D. Stereoscopy: The Dawn of 3D. May BH, editor. London: London Stereoscopic Company; 2021. 
2. Bernard F, Richard P, Kahn A, Fournier HD. Does 3D stereoscopy support anatomical education? Surg Radiol Anat. 2020 Jul;42(7):843–852. doi: 10.1007/s00276-020–02465‑z. Epub 2020 Apr 4. PMID: 32248256.
3. Cunningham DJ. Stereoscopic studies of anatomy, vol 3. New York: Imperial Publishing Company; 1911.
4. Cunningham DJ. Stereoscopic studies of anatomy, vol 2. New York: Imperial Publishing Company; 1909.
5. Bassett DL. A Stereoscopic Atlas of Human Anatomy. Portland, Oregon: Sawyer’s Inc.; 1962.
6. Cui D, Wilson TD, Rockhold RW, Lehman MN, Lynch JC. Evaluation of the effectiveness of 3D vascular stereoscopic models in anatomy instruction for first year medical students. Anatomical Sciences Edu. 2016 Jun;10(1):34–45. doi: 10.1002/ase.1626
7. Goodarzi A, Monti S, Lee D, Girgis F. Effect of Stereoscopic Anaglyphic 3‑Dimensional Video Didactics on Learning Neuroanatomy. World Neurosurg. 2017 Nov;107:35–39. doi: 10.1016/j.wneu.2017.07.119. Epub 2017 Jul 29. PMID: 28765017.
8. Luursema JM, Verwey WB, Kommers PAM, Annema JH. The role of stereopsis in virtual anatomical learning. Interacting with Computers. 2008 Sep;20(4–5):455–460. doi: 10.1016/j.intcom.2008.04.003
9. Cui D, Lynch JC, Smith AD, Wilson TD, Lehman MN. Stereoscopic vascular models of the head and neck: A computed tomography angiography visualization. Anat Sci Educ. 2016 Mar-Apr;9(2):179–85. doi: 10.1002/ase.1537. Epub 2015 Apr 30. PMID: 25929248.
10. Jacquesson T, Simon E, Dauleac C, Margueron L, Robinson P, Mertens P. Stereoscopic three-dimensional visualization: interest for neuroanatomy teaching in medical school. Surg Radiol Anat. 2020 Jun;42(6):719–727. doi: 10.1007/s00276-020–02442‑6. Epub 2020 Feb 29. PMID: 32114650.
11. Rolland JP, Wright DL, Kancherla AR. Towards a novel augmented-reality tool to visualize dynamic 3‑D anatomy. Stud Health Technol Inform. 1997;39:337–48. PMID: 10168929.
12. Unger B, Tordon B, Pisa J, Hochman JB. Importance of Stereoscopy in Haptic Training of Novice Temporal Bone Surgery. Stud Health Technol Inform. 2016;220:439–45. PMID: 27046619.
13. Erolin C, Lamb C, Soames R, Wilkinson C. Does Virtual Haptic Dissection Improve Student Learning? A Multi-Year Comparative Study. Stud Health Technol Inform. 2016;220:110–7. PMID: 27046562.
14. Christopher LA, William AMS, Cohen-Gadol AA. Future Directions in 3‑Dimensional Imaging and Neurosurgery Stereoscopy and Autostereoscopy. Neurosurg. 2013;72:A131-A138. doi: 10.1227/NEU.0b013e318270d9c0
15. Uluç K, Kujoth GC, Başkaya MK. Operating microscopes: past, present, and future. Neurosurg Focus. 2009;27:E4. doi: 10.3171/2009.6.FOCUS09120
16. Kang X, Azizian M, Wilson E, Wu K, Martin AD, Kane TD, Peters CA, Cleary K, Shekhar R. Stereoscopic augmented reality for laparoscopic surgery. Surg Endosc. 2014 Jul;28(7):2227–35. doi: 10.1007/s00464-014‑3433‑x. Epub 2014 Feb 1. PMID: 24488352.
17. Becker H, Melzer A, Schurr MO, Buess G. 3‑D video techniques in endoscopic surgery. Endosc Surg Allied Technol. 1993 Feb;1(1):40–6. PMID: 8050009.
18. Schwab K, Smith R, Brown V, Whyte M, Jourdan I. Evolution of stereoscopic imaging in surgery and recent advances. World J Gastrointest Endosc. 2017 Aug 16;9(8):368–377. doi: 10.4253/wjge.v9.i8.368. PMID: 28874957; PMCID: PMC5565502.
19. Ford E, Purger D, Tryggestad E, McNutt T, Christodouleas J, Rigamonti D, Shokek O, Won S, Zhou J, Lim M, Wong J, Kleinberg L. A virtual frame system for stereotactic radiosurgery planning. Int J Radiat Oncol Biol Phys. 2008 Nov 15;72(4):1244–9. doi: 10.1016/j.ijrobp.2008.06.1934. PMID: 18954719.
20. Ho DK. Using smartphone-delivered stereoscopic vision in microsurgery: a feasibility study. Eye (Lond). 2019 Jun;33(6):953–956. doi: 10.1038/s41433-019‑0356‑8. Epub 2019 Feb 12. PMID: 30755728; PMCID: PMC6707160.
21. Mohan A, Wara UU, Arshad Shaikh MT, Rahman RM, Zaidi ZA. Telesurgery and Robotics: An Improved and Efficient Era. Cureus. 2021 Mar 26;13(3):e14124. doi: 10.7759/cureus.14124. PMID: 33927932; PMCID: PMC8075759.
22. Zheng J, Wang Y, Zhang J, Guo W, Yang X, Luo L, Jiao W, Hu X, Yu Z, Wang C, Zhu L, Yang Z, Zhang M, Xie F, Jia Y, Li B, Li Z, Dong Q, Niu H. 5G ultra-remote robot-assisted laparoscopic surgery in China. Surg Endosc. 2020 Nov;34(11):5172–5180. doi: 10.1007/s00464-020–07823‑x. Epub 2020 Jul 22. PMID: 32700149.
23. Pateras E, Plakitsi A, Chatzipantelis A. Stereoscopic Vision & Testing Techniques – Overview. Biomed. J. Scientific and Technical Res. 2020 Mar;26(5):20252–20260. doi: 10.26717/BJSTR.2020.26.004405
24. Lang J. Der Treffversuch zur Prüfung des Stereosehens [The two-pencil test for testing stereopsis]. Klin Monbl Augenheilkd. 1983 Jun;182(6):576–81. German. doi: 10.1055/s‑2008–1054858. PMID: 6876657.
25. Nongpuir ME, Sharma P. Horizontal Lang two-pencil test as a screening test for stereopsis and binocularity. Indian Journal of Ophthalmology 58(4):287–90. doi: 10.4103/0301–4738.64125
26. Parks MM. Strabismus care: Past, present and future. Doc Opthalmol. 1973 Feb;34:301–315. doi: 10.1007/BF00151817
27. Synoptophore (Major Amblyoscope) Information Guide. HS Clement Clarke Opthalmic. Harlow, Essex: Haag-Streit UK; Nov 2014.
28. Landecker H. What do you see?. Hidden Treasure: The National Library of Medicine. New York: Blast Books; 2011
29. Borowiec-Wojtanowska A, Baranowska-George T. Leczenie chorych z małym katem zeza ćwiczeniami na telestereoskopie Starkiewicza i synoptoforze [Treatment of patients with small angle squint by exercising with Starkiewicz’s tele-stereoscopy and synoptophore]. Klin Oczna. 1994 Jun-Jul;96(6–7):197–9. Polish. PMID: 7897972.
30. Goldrich SG. Optometric therapy of divergence excess strabismus. Am J Optom Physiol Opt. 1980 Jan;57(1):7–14. doi: 10.1097/00006324–198001000-00002. PMID: 7377279.
31. Liu Y, Yip LWL, Zheng Y, Wang L. Glaucoma screening using an attention-guided stereo ensemble network. Methods. 2021 Jun 19:S1046-2023(21)00162–6. doi: 10.1016/j.ymeth.2021.06.010. Epub ahead of print. PMID: 34153436.
32. Shrestha R, Budenz DL, Mwanza JC, Tulenko SE, Fleischman D, Gower EW. Comparison of vertical cup-to-disc ratio estimates using stereoscopic and monoscopic cameras. Eye (Lond). 2021 Dec;35(12):3318–3324. doi: 10.1038/s41433-021–01395‑3. Epub 2021 Jan 29. PMID: 33514892; PMCID: PMC8602644.
33. Hasanreisoglu M, Priel E, Naveh L, Lusky M, Weinberger D, Benjamini Y, Gaton DD. Digital versus film stereo-photography for assessment of the optic nerve head in glaucoma and glaucoma suspect patients. J Glaucoma. 2013 Mar;22(3):238–42. doi: 10.1097/IJG.0b013e31823298da. PMID: 21946551.
34. Norouzifard M, Dawda A, Abdul-Rahman A, GholamHosseini H, Klette R. Superpixel segmentaion methods on stereo fundus images and disparity map for glaucoma detection. 2018 International Conference on Image and Vision Computing New Zealand (IVCNZ). 2018 Nov:1–6. doi: 10.1109/IVCNZ.2018.8634732.
35. Ferre R, Goumot PA, Mesurolle B. Stereoscopic digital mammogram: Usefulness in daily practice. J Gynecol Obstet Hum Reprod. 2018 Jun;47(6):231–236. doi: 10.1016/j.jogoh.2018.03.009. Epub 2018 Apr 3. PMID: 29621618.
36. Harake D, Gnanappa GK, Alvarez SGV, Whittle A, Punithakumar K, Boechler P, Noga M, Khoo NS. Stereoscopic Display Is Superior to Conventional Display for Three-Dimensional Echocardiography of Congenital Heart Anatomy. J Am Soc Echocardiogr. 2020 Nov;33(11):1297–1305. doi: 10.1016/j.echo.2020.06.016. Epub 2020 Sep 9. PMID: 32919855.
37. Nobuyama S, Sato T, Handa H, Nishine H, Inoue T, Mineshita M, Miyazawa T. Comparison of Airway Measurements for Tracheobronchial Stenosis Between Stereoscopic Bronchoscope and MD-CT. J Bronchology Interv Pulmonol. 2017 Oct;24(4):296–302. doi: 10.1097/LBR.0000000000000409. PMID: 28957890.
38. Tanaka C, Fujii H, Ikeda T, Jinno H, Nakahara T, Suzuki T, Kitagawa Y, Kitajima M, Ando Y, Kubo A. Stereoscopic scintigraphic imaging of breast cancer sentinel lymph nodes. Breast Cancer. 2007;14(1):92–9. doi: 10.2325/jbcs.14.92. PMID: 17245002.

Der Beitrag A Brief History and Summary of Stereoscopy in Medicine erschien zuerst auf the stereosite.

Today, it is commonly known (at least for those interested in stereoscopy) that our vision consists of two images. Our brain fuses these two images into one and lets us perceive a sense of depth caused by slight differences between the two images.

Back in the 19th century the concept of binocular vision had not yet been explored or written about anywhere. It was a scientist in his mid 30s who not only described the phenomenon later called stereopsis but also constructed a device to view two flat images in 3D which he called a stereoscope. This is especially remarkable as photography was not invented until one year later. Charles Wheatstone’s observations were based only on drawings. Most of these drawings are based on horizontal mirroring which is why we call them mirror stereos today.

Wheatstone’s paper, presented to the Royal Society of London on June 21st 1838, is organized in 16 paragraphs and is therefore quite extensive. But even if the improvements by Sir David Brewster replaced Wheatstone’s stereoscope about ten years later, his observations can still be considered as the birth of Stereoscopy. Therefore, I want to give my full recommendation to read this source entirely. Do you remember your first time looking through a stereoscope? Well, put yourself into the mindset that nothing about it is known. After a talk about binocular vision that you followed with more or less interest, you are presented with a strange-looking optical mirror toy and some hand drawings. But looking through it completely blows your mind…

If you got more interested in the theory of stereoscopy afterwards, you might also want to read David Kuntz’ articles about the baseline and the stereo window or my article about hyper stereos. I’ve also created an interactive version of the graphic in paragraph 15 which can be accessed here.

§1 §2 §3 §4 §5 §6 §7 §8 §9 §10 §11 §12 §13 §14 §15 §16

Philosophical Transactions of the Royal Society of London, Vol. 128, pp. 371 — 394

Contributions to the Physiology of Vision. — Part the First.
On some remarkable, and hitherto unobserved, Phenomena of Binocular Vision.

By CHARLES WHEATSTONE, F.R.S., Professor of Experimental Philosophy in King’s College, London.

Received and Read June 21, 1838.

§ 1.

WHEN an object is viewed at so great a distance that the optic axes of both eyes are sensibly parallel when directed towards it, the perspective projections of it, seen by each eye separately, are similar, and the appearance to the two eyes is precisely the same as when the object is seen by one eye only. There is, in such case, no difference between the visual appearance of an object in relief and its perspective projection on a plane surface; and hence pictorial representations of distant objects, when those circumstances which would prevent or disturb the illusion are carefully excluded, may be rendered such perfect resemblances of the objects they are intended to represent as to be mistaken for them; the Diorama is an instance of this. But this similarity no longer exists when the object is placed so near the eyes that to view it the optic axes must converge; under these conditions a different perspective projection of it is seen by each eye, and these perspectives are more dissimilar as the convergence of the optic axes becomes greater. This fact may be easily verified by placing any figure of three dimensions, an outline cube for instance, at a moderate distance before the eyes, and while the head is kept perfectly steady, viewing it with each eye successively while the other is closed. Plate XI. fig. 13. represents the two perspective projections of a cube; b is that seen by the right eye, and a that presented to the left eye; the figure being supposed to be placed about seven inches immediately before the spectator.

The appearances, which are by this simple experiment rendered so obvious, may be easily inferred from the established laws of perspective; for the same object in relief is, when viewed by a different eye, seen from two points of sight at a distance from each other equal to the line joining the two eyes. Yet they seem to have escaped the attention of every philosopher and artist who has treated of the subjects of vision and perspective. I can ascribe this inattention to a phenomenon leading to the important and curious consequences, which will form the subject of the present communication, only to this circumstance; that the results being contrary to a principle which was very generally maintained by optical writers, viz. that objects can be seen single only when their images fall on corresponding points of the two retinæ, an hypothesis which will be hereafter discussed, if the consideration ever arose in their minds, it was hastily discarded under the conviction, that if the pictures presented to the two eyes are under certain circumstances dissimilar, their differences must be so small that they need not be taken into account.

It will now be obvious why it is impossible for the artist to give a faithful representation of any near solid object, that is, to produce a painting which shall not be distinguished in the mind from the object itself. When the painting and the object are seen with both eyes, in the case of the painting two similar pictures are projected on the retinæ, in the case of the solid object the pictures are dissimilar; there is therefore an essential difference between the impressions on the organs of sensation in the two cases, and consequently between the perceptions formed in the mind; the painting therefore cannot be confounded with the solid object.

After looking over the works of many authors who might be expected to have made some remarks relating to this subject, I have been able to find but one, which is in the Trattato della Pittura of LEONARDO DA VINCI¹. This great artist and ingenious philosopher observes, “that a painting, though conducted with the greatest art and finished to the last perfection, both with regard to its contours, its lights, its shadows and its colours, can never show a relievo equal to that of the natural objects, unless these be viewed at a distance and with a single eye. For,” says he, “if an object C (Plate X. fig. 1.) be viewed by a single eye at A, all objects in the space behind it, included as it were in a shadow E C F cast by a candle at A, are invisible to the eye at A; but when the other eye at B is opened, part of these objects become visible to it; those only being hid from both eyes that are included, as it were, in the double shadow C D, cast by two lights at A and B, and terminated in D, the angular space E D G beyond D being always visible to both eyes. And the hidden space C D is so much the shorter, as the object C is smaller and nearer to the eyes. Thus the object C seen with both eyes becomes, as it were, transparent, according to the usual definition of a transparent thing; namely, that which hides nothing beyond it. But this cannot happen when an object, whose breadth is bigger than that of the pupil, is viewed by a single eye. The truth of this observation is therefore evident, because a painted figure intercepts all the space behind its apparent place, so as to preclude the eyes from the sight of every part of the imaginary ground behind it.”

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§ 2.

It being thus established that the mind perceives an object of three dimensions by means of the two dissimilar pictures projected by it on the two retinæ, the following question occurs: What would be the visual effect of simultaneously presenting to each eye, instead of the object itself, its projection on a plane surface as it appears to that eye? To pursue this inquiry it is necessary that means should be contrived to make the two pictures, which must necessarily occupy different places, fall on similar parts of both retinæ. Under the ordinary circumstances of vision the object is seen at the concourse of the optic axes, and its images consequently are projected on similar parts of the two retinæ; but it is also evident that two exactly similar objects may be made to fall on similar parts of the two retinæ, if they are placed one in the direction of each optic axis, at equal distances before or beyond their intersection.

Fig. 2. represents the usual situation of an object at the intersection of the optic axes. In fig. 3. the similar objects are placed in the direction of the optic axes before their intersection, and in fig. 4. beyond it. In all these three cases the mind perceives but a single object, and refers it to the place where the optic axes meet. It will be observed, that when the eyes converge beyond the objects, as in fig. 3., the right hand object is seen by the right eye, and the left hand object by the left eye; while when the axes converge nearer than the Objects, the right hand object is seen by the left eye, and conversely. As both of these modes of vision are forced and unnatural, eyes unaccustomed to such experiments require some artificial assistance.

If the eyes are to converge beyond the objects, this may be afforded by a pair of tubes (fig. 5.) capable of being inclined towards each other at various angles, so as to correspond with the different convergences of the optic axes. If the eyes are to converge at a nearer distance than that at which the objects are placed, a box (fig. 6.) may be conveniently employed; the objects a a’ are placed distant from each other, on a stand capable of being moved nearer the eyes if required, and the optic axes being directed towards them will cross at c, the aperture b b’ allowing the visual rays front the right hand object to reach the left eye, and those from the left hand object to fall on the right eye; the coincidence of the images may be facilitated by placing the point of a needle at the point of intersection of the optic axes c, and fixing the eyes upon it. In both these instruments (figs. 5. and 6.) the lateral images are hidden from view, and much less difficulty occurs in making the images unite than when the naked eyes are employed.

Now if, instead of placing two exactly similar objects to be viewed by the eyes in either of the modes above described, the two perspective projections of the same solid object be so disposed, the mind will still perceive the object to be single, but instead of a representation on a plane surface, as each drawing appears to be when separately viewed by that eye which is directed towards it, the observer will perceive a figure of three dimensions, the exact counterpart of the object from which the drawings were made. To make this matter clear I will mention one or two of the most simple cases.

If two vertical lines near each other, but at different distances from the spectator, be regarded first with one eye and then with the other, the distance between them when referred to the same plane will appear different; if the left hand line be nearer to the eyes the distance as seen by the left eye will be less than the distance as seen by the right eye; fig. 7. will render this evident; a a’ are vertical sections of the two original lines, and b b’ the plane to which their projections are referred. Now if the two lines be drawn on two pieces of card, at the respective distances at which they appear to each eye, and these cards be afterwards viewed by either of the means above directed, the observer will no longer see two lines on a plane surface, as each card separately shows ; but two lines will appear, one nearer to him than the other, precisely as the original vertical lines themselves. Again, if a straight wire be held before the eyes in such a position that one of its ends shall be nearer to the observer than the other is, each eye separately referring it to a plane perpendicular to the common axis, will see a line differently inclined ; and then if lines having the same apparent inclinations be drawn on two pieces of card. and be presented to the eyes as before directed, the real position of the original line will be correctly perceived by the mind.

In the same manner the most complex figures of three dimensions may be accurately represented to the mind, by presenting their two perspective projections to the two retinæ. But I shall defer these more perfect experiments until I describe an instrument which will enable any person to observe all the phenomena in question with the greatest ease and certainty.

In the instruments above described the optic axes converge to some point in a plane before or beyond that in which the objects to be seen are situated. The adaptation of the eye, which enables us to see distinctly at different distances, and which habitually accompanies every different degree of convergence of the optic axes, does not immediately adjust itself to tIme new and unusual condition ; and to persons not accustomed to experiments of this kind, the pictures will either not readily unite, or will appear dim and confused. Besides this, no object can be viewed according to either mode when the drawings exceed in breadth the distance of the two points of the optic axes in which their centres are placed.

These inconveniences are removed by the instrument I am about to describe; the two pictures (or rather their reflected images) are placed in it at the true concourse of the optic axes, the focal adaptation of the eye preserves its usual adjustment, the appearance of lateral images is entirely avoided, and a large field of view for each eye is obtained. The frequent reference I shall have occasion to make to this instrument, will render it convenient to give it a specific name, I therefore propose that it be called a stereoscope, to indicate its property of representing solid figures.

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§ 3.

The stereoscope is represented by figs. 8. and 9; the former being a front view, and the latter a plan of the instrument. A A’ are two plane mirrors, about four inches square, inserted in frames, and so adjusted that their backs form an angle of 90° with each other; these mirrors are fixed by their common edge against an upright B, or which was less easy to represent in the drawing, against the middle line of a vertical board, cut away in such manner as to allow the eyes to be placed before the two mirrors. C C’ are two sliding boards, to which are attached the upright boards D D’, which may thus be removed to different distances from the mirrors. In most of the experiments hereafter to be detailed, it is necessary that each upright board shall be at the same distance from the mirror which is opposite to it. To facilitate this double adjustment, I employ a right and a left-handed wooden screw, r l; the two ends of this compound screw pass through the nuts e e’, which are fixed to the lower parts of the upright boards D D’, so that by turning the screw pin p one way the two boards will approach, and by turning it the other they will recede from each other, one always preserving the same distance as the other from the middle line f. E E’ are pannels, to which the pictures are fixed in such manner that their corresponding horizontal lines shall be on the same level: these pannels are capable of sliding backwards and forwards in grooves on the upright boards D D’. The apparatus having been described, it flow remains to explain the manner of using it. The observer must place his eyes as near as possible to the mirrors, the right eye before the right hand mirror, and the left eye before the left hand mirror, and he must move the sliding pannels E E’ to or from him until the two reflected images coincide at the intersection of the optic axes, and form an image of the same apparent magnitude as each of the component pictures. The pictures will indeed coincide when the sliding pannels are in a variety of different positions, and consequently when viewed under different inclinations of the optic axes; but there is only one position in which the binocular image will be immediately seen single, of its proper magnitude, and without fatigue to the eyes, because in this position only the ordinary relations between the magnitude of the pictures on the retina, the inclination of the optic axes, and the adaptation of the eye to distinct vision at different distances are preserved. The alteration in the apparent magnitude of the binocular images, when these usual relations are disturbed, will be discussed in another paper of this series, with a variety of remarkable phenomena depending thereon. In all the experiments detailed in the present memoir I shall suppose these relations to remain undisturbed, and the optic axes to converge about six or eight inches before the eyes.

If the pictures are all drawn to be seen with the same inclination of the optic axes, the apparatus may be simplified by omitting the screw r 1 and fixing the upright boards D D’ at the proper distances. The sliding pannels may also be dispensed with, and the drawings themselves be made to slide in the grooves.

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§ 4.

A few of outline figures, calculated to give rise to the perception of objects of three dimensions when placed in the stereoscope in the manner described, are represented from figs. 10. to 20. They are one half the linear size of the figures actually employed. As the drawings are reversed by reflection in the mirrors, I will suppose these figures to be the reflected images to which the eyes are directed in the apparatus; those marked b being seen by the right eye, and those marked a by the left eye. The drawings, it has been already explained, are two different projections of the same object seen from two points of sight, the distance between which is equal to the interval between the eyes of the observer; this interval is generally about 2½ inches.

a and b, fig. 10. will, when viewed in the stereoscope, present to the mind a line in the vertical plane, with its lower end inclined towards the observer. If the two component lines be caused to turn round their centres equally in opposite directions, the resultant line will, while it appears to assume every degree of inclination to the referent plane, still seem to remain in the same vertical plane.

Fig. 11. A series of points all in the same horizontal plane, but each towards the right hand successively nearer the observer.

Fig. 12. A curved line intersecting the referent plane, and having its convexity towards the observer.

Fig. 13. A cube.

Fig. 14. A cone, having its axis perpendicular to the referent plane, and its vertex towards the observer.

Fig. 15. The frustum of a square pyramid; its axis perpendicular to the referent plane, and its base furthest from the eye.

Fig. 16. Two circles at different distances from the eyes, their centres in the same perpendicular, forming the outline of the frustum of a cone.

The other figures require no observation.

For the purposes of illustration I have employed only outline figures, for had either shading or colouring been introduced it might be supposed that the effect was wholly or in part due to these circumstances, whereas by leaving them out of consideration no room is left to doubt that the entire effect of relief is owing to the simultaneous perception of the two monocular projections, one on each retina. But if it be required to obtain the most faithful resemblances of real objects, shadowing and colouring may properly be employed to heighten the effects. Careful attention would enable an artist to draw and paint the two component pictures, so as to present to the mind of the observer, in the resultant perception, perfect identity with the object represented. Flowers, crystals, busts, vases, instruments of various kinds, &c., might thus be represented so as not to be distinguished by sight from the real objects themselves.

It is worthy of remark, that the process by which we thus become acquainted with the real forms of solid objects, is precisely that which is employed in descriptive geometry, an important science we owe to the genius of MONGE, but which is little studied or known in this country. In this science, the position of a point, a right line or a curve, and consequently of any figure whatever, is completely determined by assigning its projections on two fixed planes, the situations of which are known, and which are not parallel to each other. In the problems of descriptive geometry the two referent planes are generally assumed to be at right angles to each other, but in binocular vision the inclination of these planes is less according as the angle made at the concourse of the optic axes is less ; thus the same solid object is represented to the mind by different pairs of monocular pictures, according as they are placed at a different distance before the eyes, and the perception of these differences (though we seem to be unconscious of them) may assist in suggesting to the mind the distance of the object. The more inclined to each other the referent planes are, with the greater accuracy are the various points of the projections referred to their proper places; and it appears to be a useful provision that the real forms of those objects which are nearest to us are thus more determinately apprehended than those which are more distant.

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§ 5.

A very singular effect is produced when the drawing originally intended to be seen by the right eye is placed at the left hand sidle of the stereoscope, and that designed to be seen by the left eye is placed on its right hand side. A figure of three dimensions, as bold in relief as before, is perceived, but it has a different form from that which is seen when the drawings are in their proper places. There is a certain relation between the proper figure and this, which I shall call its converse figure. Those points which are nearest the observer in the proper figure are the most remote from him in the converse figure, and vice versâ, so that the figure is, as it were, inverted; but it is not an exact inversion, for the near parts of the converse figure appear smaller, and the remote parts larger than the same parts before the inversion. Hence the drawings which, properly placed, occasion a cube to be perceived, when changed in the manner described, represent the frustum of a square pyramid with its base remote from the eye: the cause of this is easy to understand.

This conversion of relief may be shown by all the pairs of drawings from fig. 10. to 19. In the case of simple figures like these the converse figure is as readily apprehended as the original one, because it is generally a figure of as frequent occurrence; hut in the vase of a more complicated figure, an architectural design, for instance, the mind, unaccustomed to perceive its converse, because it never occurs in nature, can find no meaning in it.

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§ 6.

The same image is depicted on the retina by an object of three dimensions as by its projection on a plane surface, provided the point of sight remain in both cases the same. There should be, therefore, no difference in the binocular appearance of two drawings, one presented to each eye, and of two real objects so presented to the two eyes that their projections on the retina shall be the same as those arising from the drawings. The following experiments will prove the justness of this inference.

I procured several pairs of skeleton figures, i. e. outline figures of three dimensions, formed either of iron wire or of ebony beading about one tenth of an inch in thickness. The pair I most frequently employed consisted of two cubes, whose sides were three inches in length. When I placed these skeleton figures on stands before the two mirrors of the stereoscope, the following effects were produced, according as their relative positions were changed. 1st. When they were so placed that the pictures which their reflected images projected on the two retinæ were precisely the same as those which would have been projected by a cube placed at the concourse of the optic axes, a cube in relief appeared before the eyes. 2ndly. When they were so placed that their reflected images projected exactly similar pictures on the two retinæ, all effect of relief was destroyed, and the compound appearance was that of an outline representation on a plane surface. 3rdly. When the cubes were so placed that the reflected image of one projected on the left retina the same picture as in the first case was projected on the right retina, and conversely, the converse figure in relief appeared.

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§7.

If a symmetrical object, that is one whose right and left sides are exactly similar to each other but inverted, be placed so that any point in the plane which divides it into these two halves is equally distant from the two eyes, its two monocular projections are, it is easy to see, inverted facsimiles of each other. Thus fig. 15, a and b are symmetrical monocular projections of the frustum of a four-sided pyramid, and figs. 13. 14. 16. are corresponding projections of other symmetrical objects. This being kept in view, I will describe an experiment which, had it been casually observed previous to the knowledge of the principles developed in this paper, would have appeared an inexplicable optical illusion.

M and M’ (fig. 21.) are two mirrors, inclined so that their faces form an angle of 90° with each other. Between them in the bisecting plane is placed a plane outline figure, such as fig. 15 a, made of card all parts but the lines being cut away, or of wire. A reflected image of this outline, placed at A, will appear behind each mirror at B and B’, and one of these images will be the inversion of the other. If the eyes be made to converge at C, it is obvious that these two reflected images will fall on corresponding parts of the two retinæ, and a figure of three dimensions will be perceived; if the outline placed in the bisecting plane be reversed, the converse skeleton form will appear; in both these experiments we have the singular phenomenon of the conversion of a single plane outline into a figure of three dimensions. To render the binocular object more distinct, concave lenses may be applied to the eyes; and to prevent the two lateral images from being seen, screens may be placed at D and D’.

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§ 8.

An effect of binocular perspective may be remarked in a plate of metal, the surface of which has been made smooth by turning it in a lathe. When a single candle is brought near such a plate, a line of light appears standing out from it, one half being above, and the other half below the surface; the position and inclination of this line chances with the situation of the light and of the observer, but it always passes through the centre of the plate. On closing the left eye the relief disappears, and the luminous line coincides with one of the diameters of the plate; on closing the right eye the line appears equally in the plane of the surface, but coincides with another diameter; on opening both eyes it instantly starts into relief². The case here is exactly analogous to the vision of two inclined lines (fig. 10.) when each is presented to a different eye in the stereoscope. It is curious, that an effect like this, which it must have been seen thousands of times, should never have attracted sufficient attention to have been made the subject of philosophic observation. It was one of the earliest facts which drew my attention to the subject I am now treating.

Dr. SMITH³ was very much puzzled by an effect of binocular perspective which he observed, but was unable to explain. He opened a pair of compasses, and while he held the joint in his hand, and the points outwards and equidistant from his eyes, and somewhat higher than the joint, he looked at a more distant point ; the compasses appeared double. He then compressed the legs until the two inner points coincided; having done this the two inner legs also entirely coincided, and bisected the angle formed by the outward ones, appearing longer and thicker than they did, and reaching from the hand to the remotest object in view. The explanation offered by Dr. SMITH accounts only for the coincidence of the points of the compasses, not for that of the entire leg. The effect in question is best seen by employing a pair of straight wires, about a foot in length. A similar observation, made with two flat rulers, and afterwards with silk threads, induced Dr. WELLS to propose a new theory of visible direction in order to explain it, so inexplicable did it seem to him by any of the received theories.

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§ 9.

The preceding experiments render it evident that there is an essential difference in the appearance of objects when seen with two eyes, and when only one eye is employed, and that the most vivid belief of the solidity of an object of three dimensions arises from two different perspective projections of it being simultaneously presented to the mind. How happens it then, it may be asked, that persons who see with only one eye form correct notions of solid objects, and never mistake them for pictures? and how happens it also, that a person having the perfect use of both eyes, perceives no difference in objects around him when he shuts one of them? To explain these apparent difficulties, it must be kept in mind, that although the simultaneous vision of two dissimilar pictures suggests the relief of objects in the most vivid manner, yet there are other signs which suggest the same ideas to the mind, which, though more ambiguous than the former, become less liable to lead the judgment astray in proportion to the extent of our previous experience. The vividness of relief arising from the projection of two dissimilar pictures, one on each retina, becomes less and less as the object is seen at a greater distance before the eyes, and entirely ceases when it is so distant that the optic axes are parallel while regarding it. We see with both eyes all objects beyond this distance precisely as we see near objects with a single eye; for the pictures on the two retinæ are then exactly similar, and the mind appreciates no difference whether two identical pictures fall on corresponding parts of the two retinæ, or whether one eye is impressed with only one of these pictures. A person deprived of the sight of one eye sees therefore all external objects, near and remote, as a person with both eyes sees remote objects only, but that vivid effect arising from the binocular vision of near objects is not perceived by the former; to supply this deficiency he has recourse unconsciously to other means of acquiring more accurate information. The motion of the head is the principal means he employs. That the required knowledge may be thus obtained will be evident from the following considerations. The mind associates with the idea of a solid object every different projection of it which experience has hitherto afforded; a single projection may be ambiguous, from its being also one of the projections of a picture, or of a different solid object; but when different projections of the same object are successively presented, they cannot all belong to another object, and the form to which they belong is completely characterized. While the object remains fixed, at every movement of the head it is viewed from a different point of sight, and the picture on the retina consequently continually changes.

Every one must be aware how greatly the perspective effect of a picture is enhanced by looking at it with only one eye, especially when a tube is employed to exclude the vision of adjacent objects, whose presence might disturb the illusion. Seen under such circumstances from the proper point of sight, the picture projects the same lines, shades and colours on the retina, as the more distant scene which it represents would do were it substituted for it. The appearance which would make us certain that it is a picture is excluded from the sight, and the imagination has room to be active. Several of the older writers erroneously attributed this apparent superiority of monocular vision to the concentration of the visual power in a single eye⁴.

There is a well-known and very striking illusion of perspective which deserves a passing remark, because the reason of the effect does not appear to be generally understood. When a perspective of a building is projected on a horizontal plane, so that the point of sight is in a line greatly inclined towards the plane, the building appears to a single eye placed at the point of sight to be in bold relief, and the illusion is almost as perfect as in the binocular experiments described in §§ 2, 3, 4. This effect wholly arises from the unusual projection, which suggests to the mind more readily the object itself than the drawing of it; for we are accustomed to see real objects in almost every point of view, but perspective representations being generally made in a vertical plane with the point of sight in a line perpendicular to the plane of projection, we are less familiar with the appearance of other projections. Any other unusual projection will produce the same effect.

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§ 10.

If we look with a single eye at the drawing of a solid geometrical figure, it may be imagined to be the representation of either of two dissimilar solid figures, the figure intended to be represented, or its converse figure (§ 5.). If the former is a very usual, and the latter a very unusual figure, the imagination will fix itself on the original without wandering to the converse figure; but if both are of ordinary occurrence, which is generally the case with regard to simple forms, a singular phenomenon takes place; it is perceived at one time distinctly as one of these figures, at another time as the other, and while one figure continues it is not in the power of the will to change it immediately.

The same phenomenon takes place, though less decidedly, when the drawing is seen with both eyes. Many of my readers will call to mind the puzzling effect of some of the diagrams annexed to the problems of the eleventh book of Euclid; which, when they were attentively looked at, changed in an arbitrary manner from one solid figure to another, and would obstinately continue to present the converse figures when the real figures alone were wanted. This perplexing illusion must be of coimmon occurrence, but I have only found one recorded observation relating to the subject. It is by Professor NECKER of Geneva, and I shall quote it in his own words from the Philosophical Magazine, Third Series, vol. i. p. 337.

“The object I have now to call your attention to is an observation which has often occurred to me while examining figures and engraved plates of crystalline forms; I mean a sudden and involuntary change in the apparent position of a crystal or solid represented in an engraved figure. What I mean will be more easily understood from the figure annexed (fig. 22.). The rhomboid A X is drawn so that the solid angle A should be seen the nearest to the spectator, and the solid angle X the farthest from him, and that the face A C D B should be the foremost, while the face X D C is behind. But in looking repeatedly at the same figure, you will perceive that at times the apparent position of the rhomboid is so changed that the solid angle X will appear the nearest, and the solid angle A the farthest; and that the face A C D B will recede behind the face X D C, which will come forward, which effect gives to the whole solid a quite contrary apparent inclination.”

Professor NECKER attributes this alteration of appearance, not to a mental operation, but to an involuntary change in the adjustment of the eye for obtaining distinct vision. He supposed that whenever the point of distinct vision on the retina is directed on the angle A, for instance, this angle seen more distinctly than the others is naturally supposed to be nearer and foremost, while the other angles seen indistinctly are supposed to be farther and behind, and that the reverse takes place when the point of distinct vision is brought to bear on the angle X.

That this is not the true explanation, is evident from three circumstances: in the first place, the two points A and X being both at the same distance from the eyes, the same alteration of adjustment which would make one of them indistinct would make the other so ; secondly, the figure will undergo the same changes whether the focal distance of the eye be adjusted to a point before or beyond the plane in which the figure is drawn; and thirdly, the change of figure frequently occurs while the eye continues to look at the same angle. The effect seems entirely to depend on our mental contemplation of the figure intended to be represented, or of its converse. By following the lines with the eye with a clear idea of the solid figure we are describing, it may be fixed for any length of time; but it requires practice to do this or to change the figure at will. As I have before observed, these effects are far more obvious when the figures are regarded with one eye only.

No illusion of this kind can take place when an object of three dimensions is seen with both eyes while the optic axes make a sensible angle with each other, because the appearance of the two dissimilar images, one to each eye, prevents the possibility of mistake. But if we regard an object at such a distance that its two projections are sensibly identical, and if this projection be capable of a double interpretation, the illusion may occur. Thus a placard on a pole carried in the streets, with one of its sides inclined towards the observer, will, when he is distant from it, frequently appear inclined in a contrary direction. Many analogous instances might be adduced, but this will suffice to call others to mind ; it must however be observed, that when shadows, or other means capable of determining the judgement are present, these fallacies do not arise.

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§ 11.

The same indetermination of judgement which causes a drawing to be perceived by the mind at different times as two different figures, frequently gives rise to a false perception when objects in relief are regarded with a single eye. The apparent conversion of a cameo into an intaglio, and of an intaglio into a cameo, is a well-known instance of this fallacy in vision; but the fact does not appear to me to have been correctly explained, nor the conditions under which it occurs to have been properly stated.

This curious illusion, which has been the subject of much attention, was first observed at one of the early meetings of the Royal Society⁵. Several of the members looking through a compound microscope of a new construction at a guinea, some of them imagined the image to be depressed, while others thought it to be embossed, as it really was. Professor GMELIN, of Wurtemburg, published a paper on the same subject in the Philosophical Transactions for 1745 ; his experiments were made with telescopes and compound microscopes which inverted the images; and he observed that the conversion of relief appeared in some cases and not in others, at some times and not at others, and to some eyes also and not to others. He endeavoured to ascertain some of the conditions of the two appearances; “but why these things should so happen,” says he, “I do not pretend to determine.”

Sir DAVID BREWSTER accounts for the fallacy in the following manner:⁶ — “A hollow seal being illuminated by a window or a candle, its shaded side is of course on the same side with the light. If we now invert the seal with one or more lenses, so that it may look in the opposite direction, it will appear to the eye with the shaded side furthest from the window. But as we know that the window is still on our left hand, and as every body with its shaded side furthest from the light must necessarily be convex or protuberant, we immediately believe that the hollow seal is now a cameo or bas-relief. The proof which the eye thus receives of the seal being raised, overcomes the evidence of its being hollow, derived from our actual knowledge and from the sense of touch. In this experiment the deception takes place from our knowing the real direction of the light which falls on the seal ; for if the place of the window, with respect to the seal, had been inverted as well as the seal itself, the illusion could not have taken place. The illusion, therefore, under our consideration is the result of an operation of our own minds, whereby we judge of the forms of bodies by the knowledge we have acquired of light and shadow. Hence the illusion depends on the accuracy and extent of our knowledge on this subject; and while some persons are under its influence, others are entirely insensible to it.”

These considerations do not fully explain the phenomenon, for they suppose that the image must be inverted, and that the light must fall in a particular direction but the conversion of relief will still take place when the object is viewed through an open tube without any lenses to invert it, and also when it is equally illuminated in all parts. The true explanation I believe to be the following. If we suppose a cameo and an intaglio of the same object, the elevations of the one corresponding exactly to the depressions of the other; it is easy to show that the projection of either on the retina is sensibly the same. When the cameo or the intaglio is seen with both eyes, it is impossible to mistake an elevation for a depression, for reasons which have been already amply explained; but when either is seen with one eye only, the most certain guide of our judgement, viz. the presentation of a different picture to each eye, is wanting; the imagination therefore supplies the deficiency, and we conceive the object to be raised or depressed according to the dictates of this faculty. No doubt in such cases our judgement is in a great degree influenced by accessory circumstances, and the intaglio or the relief may sometimes present itself according to our previous knowledge of the direction in which the shadows ought to appear; but the real cause of the phenomenon is to be found in the indetermination of the judgement arising from our more perfect means of judging being absent.

Observers with the microscope must be particularly on their guard against illusions of this kind. RASPAIL observes⁷ that the hollow pyramidal arrangement of the crystals of muriate of soda appears, when seen through a microscope, like a striated pyramid in relief. He recommends two modes of correcting the illusion. The first is to bring successively to the focus of the instrument the different parts of the crystal; if the pyramid be in relief, the point will arrive at the focus sooner than the base will; if the pyramid be hollow, the contrary will take place. The second mode is to project a strong light on the pyramid in the field of view of the microscope, and to observe which sides of the crystal are illuminated, taking however the inversion of the image into consideration if a compound microscope be employed.

The inversion of relief is very striking when a skeleton cube is looked at with one eye, and the following singular results may in this case be observed. So long as the mind perceives the cube, however the figure be turned about, its various appearances will be but different representations of the same object, and the same primitive form will be suggested to the mind by all of them: but it is not so if the converse figure fixes the attention; the series of successive projections cannot then be referred to any figure to which they are all common, and the skeleton figure will appear to be continually undergoing a change of shape.

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§ 12.

I have given ample proof that objects whose pictures do not fall on corresponding points of the two retinæ may still appear single. I will now adduce an experiment which proves that similar pictures falling on corresponding points of the two retinæ may appear double and in different places.

Present, in the stereoscope, to the right eye a vertical line, and to the left eye a line inclined some degrees from the perpendicular (fig. 23.); the observer will then perceive, as formerly explained, a line, the extremities of which appear at different distances before the eyes. Draw on the left hand figure a faint vertical line exactly corresponding in position and length to that presented to the right eye; and let the two lines of this left hand figure intersect each other at their centres. Looking now at these two drawings in the stereoscope, the two strong lines, each seen by a different eye, will coincide, and the resultant perspective line will appear to occupy the same place as before; but the faint line which now falls on a line of the left retina, which corresponds with the line of the might retina on which one of the coinciding strong lines, viz. the vertical one, falls, appears in a different place. The place this faint line apparently occupies is the intersection of that plane of visual direction of the left eye in which it is situated, with the plane of visual direction of the right eye, which contains the strong vertical line.

This experiment affords another proof that there is no necessary physiological connection between the corresponding points of the two retinæ,—a doctrine which has been maintained by so many authors.

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§ 13. 

Binocular Vision of Images of different Magnitudes.

We will now inquire what effect results from presenting similar images, differing only in magnitude, to analogous parts of the two retinæ. For this purpose two squares or circles, differing obviously but not extravagantly in size, may be drawn on two separate pieces of paper, and placed in the stereoscope so that the reflected image of each shall he equally distant from the eye by which it is regarded. It will then be seen that, notwithstanding this difference, they coalesce and occasion a single resultant perception. The limit of the difference of size within which the single appearance subsists may be ascertained by employing two images of equal magnitude, and causing one of them to recede from the eye while the other remains at a constant distance ; this is effected merely by pulling out the sliding board C (fig. 8.) while the other C’ remains fixed, the screw having previously been removed.

Though the single appearance of two images of different size is by this experiment demonstrated, the observer is unable to perceive what difference exists between the apparent magnitude of the binocular image and that of the two monocular images to determine this point the stereoscope must be dispensed with, and the experiment so arranged that all three shall be simultaneously seen ; which may be done in the following manner:—The two drawings being placed side by side on a plane before the eyes, the optic axes must be made to converge to a nearer point as at fig. 4., or to a more distant one as at fig. 3., until the three images are seen at the same time, the binocular image in the middle, and the monocular images at each side. It will thus be seen that the binocular image is apparently intermediate in size between the two monocular ones.

If the pictures be too unequal in magnitude, the binocular coincidence does not take place. It appears that if the inequality of the pictures be greater than the difference which exists between the two projections of the same object when seen in the most oblique position of the eyes (i. e. both turned to the extreme right or to the extreme left), ordinarily employed, they do not coalesce. Were it not for the binocular coincidence of two images of different magnitude, objects would appear single only when the optic axes converge immediately forwards; for it is only when the converging visual lines form equal angles with the visual base (the line joining the centres of the two eyes) as at fig. 2., that the two pictures can be of equal magnitude; but when they form different angles with it, as at fig. 24., the distance from the object to each eye is different, and consequently the picture projected on each retina has a different magnitude. If a piece of money be held in the position a, (fig. 24.) while the optic axes converge to a nearer point c, it will appear double, and that seen by the left eye will be evidently smaller than the other.

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§ 14. 

Phenomena which are observed when objects of different forms are simultaneously presented to corresponding parts of the two retinæ.

If we regard a picture with the right eye alone for a considerable length of time it will be constantly perceived; if we look at another and dissimilar picture with the left eye alone its effect will be equally permanent; it might therefore be expected, that if each of these pictures were presented to its corresponding eye at the same time the two would appear permanently superposed on each other. This, however, contrary to expectation, is not the case.

If a and b (fig. 25.) are each presented at the same time to a different eye, the common border will remain constant, while the letter within it will change alternately from that which would be perceived by the right eye alone to that which would be perceived by the left eye alone. At the moment of change the letter which has just been seen breaks into fragments, while fragments of the letter which is about to appear mingle with them, and are immediately after replaced by the entire letter. It does not appear to be in the power of the will to determine the appearance of either of the letters, but the duration of the appearance seems to depend on causes which are under our control: thus if the two pictures be equally illuminated, the alternations appear in general of equal duration; but if one picture be in ore illuminated than the other, that which is less so will be perceived during a shorter time. I have generally made this experiment with the apparatus, fig. 6. When complex pictures are employed in the stereoscope, various parts of them alternate differently.

There are some facts intimately connected with the subject of the present article which have already been frequently observed. I allude to the experiments, first made by DU TOUR, in which two different colours are presented to corresponding parts of the two retinæ. If a blue disc be presented to the right eye and a yellow disc to the corresponding part of the left eye, instead of a green disc which would appear if these two colours had mingled before their arrival at a single eye, the mind will perceive the two colours distinctly one or the other alternately predominating either partially or wholly over the disc. In the same manner the mind perceives no trace of violet when red is presented to one eye and blue to the other, nor any vestige of orange when red and yellow are separately presented in a similar manner. These experiments may be conveniently repeated by placing the coloured discs in the stereoscope, but they have been most usually made by looking at a white object through differently coloured glasses, one applied to each eye.

In some authors we find it stated, contrary to fact, that if similar objects of different colour be presented one to each eye, the appearance will be that compounded of the two colours. Dr. REID⁸ and JANIN are among the writers who have fallen into this inconsiderate error, which arose no doubt from their deciding according to previous notions, instead of ascertaining by experiment what actually does happen.

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§ 15.

No question relating to vision has been so much debated as the cause of the single appearance of objects seen by both eyes. I shall in the present section give a slight review of the various theories which have been advanced by philosophers to account for this phenomenon, in order that the remarks I have to make in the succeeding section may be properly understood.

The law of visible direction for monocular vision has been variously stated by different optical writers. Some have maintained with Dr’s. REID and PORTERFIELD, that every external point is seen in the direction of a line passing from its picture on the retina through the centre of the eye; while others have supposed with Dr. SMITH that the visible direction of an object coincides with the visual ray, or the principal ray of the pencil which flows from it to the eye. D’ALEMBERT, furnished with imperfect data respecting the refractive densities of the humours of the eye, calculated that the apparent magnitudes of objects would differ widely on the two suppositions, and concluded that the visible point of an object was not seen in either of these directions, but sensibly in the direction of a line joining the point itself and its image on the retina; but he acknowledged that he could assign no reason for this law. Sir DAVID BREWSTER, provided with more accurate data, has shown that these three lines so nearly coincide with each other, that “at an inclination of 30°, a line perpendicular to the point of impression on the retina passes through the common centre, and does not deviate from the real line of visible direction more than half a degree, a quantity too small to interfere with the purposes of vision.” We may, therefore, assume in all our future reasonings the truth of the following definition given by this eminent philosopher :—“ As the interior eye-ball is as nearly as possible a perfect sphere, lines perpendicular to the surface of the retina must all pass through one single point, namely the centre of its spherical surface. This one point may be called the centre of visible direction, because every point of a visible object will be seen in the direction of a line drawn from this centre to the visible point.”

It is obvious, that the result of any attempt to explain the single appearance of objects to both eyes, or, in other words, the law of visible direction for binocular vision, ought to contain nothing inconsistent with the law of visible direction for monocular vision.

It was the opinion of AGUILONIUS, that all objects seen at the same glance with both eyes appear to be in the plane of the horopter. The horopter he defines to be a line drawn through the point of intersection of the optic axes, and parallel to the line joining the centres of the two eyes; the plane of the horopter to be a plane passing through this line at right angles to that of the optic axes. All objects which are in this plane, must, according to him, appear single because the lines of direction in which any point of an object is seen coincide only in this plane and nowhere else; and as these lines can meet each other only in one point, it follows from the hypothesis, that all objects not in the plane of the horopter must appear double, because their lines of direction intersect each other, either before or after they pass through it. This opinion was also maintained by DECHALES and PORTERFIELD. That it is erroneous, I have given, I think, sufficient proof, in showing that, when the optic axes converge to any point, objects before or beyond the plane of the horopter are under certain circumstances equally seen single as those in that plane.

Dr. WELLS’S “new theory of visible direction” was a modification of the preceding hypothesis. This acute writer held with AGUILONIUS, that objects are seen single only when they are in the plane of the horopter, and consequently that they appear double when they are either before or beyond it; but he attempted to make this single appearance of objects only in the plane of the horopter to depend on other principles, from which he deduced, contrary to AGUILONIUS, that the objects which are doubled do not appear in the plane of the horopter, but in other places which are determined by these principles. Dr. WELLS was led to his new theory by a fact which he accidentally observed, and which he could not reconcile with any existing theory of visible direction ; this fact had, though he was unaware of it, been previously noticed by Dr. SMITH; it is already mentioned in § 8., and is the only instance of binocular vision of relief which I have found recorded previous to my own investigations. So little does Dr. WELLS’S theory appear to have been understood, that no subsequent writer has attempted either to confirm or disprove his opinions. It would be useless here to discuss the principles of this theory, which was framed to account for an anomalous individual fact, since it is inconsistent with the general rules on which that fact has been now shown to depend. Notwithstanding these erroneous views, the “essay upon single vision with two eyes” contains many valuable experiments and remarks, the truth of which are independent of the theory they were intended to illustrate.

The theory which has obtained greatest currency is that which assumes that an object is seen single because its pictures fall on corresponding points of the two retinæ, that is on points which are similarly situated with respect to the two centres both in distance and position. This theory supposes that the pictures projected on the retinæ are exactly similar to each other, corresponding points of the two pictures falling on corresponding points of the two retinæ. Authors who agree with regard to this property, differ widely in explaining why objects are seen in the same place, or single, according to this law. Dr. SMITH makes it to depend entirely on custom, and explains why the eyes are habitually directed towards an object so that its pictures fall on corresponding parts in the following manner:—“ When we view an object steadily, we have acquired a habit of directing the optic axes to the point in view; because its pictures falling upon the middle points of the retinas, are then distincter than if they fell upon any other places; and since the pictures of the whole object are equal to one another, and are both inverted with respect to the optic axes, it follows that the pictures of any collateral point are painted upon corresponding points of the retinas.”

Dr. REID, after a long dissertation on the subject, concludes, “that by an original property of human eyes, objects painted upon the centres of the two retinæ, or upon points similarly situated with regard to the centres, appear in the same visible place; that the most plausible attempts to account for this property of the eyes have been unsuccessful ; and therefore, that it must be either a primary law of our constitution, or the consequence of some more general law which is not yet discovered.”

Other writers who have admitted this principle have regarded it as arising from anatomical structure and dependent on connexion of nervous fibres; among these stand the names of GALEN, Dr. BRIGGS, Sir ISAAC NEWTON, ROHAULT, Dr. HARTLEY, Dr. WOLLASTON and Professor MÜLLER.

Many of the supporters of the theory of corresponding points have thought, or rather have admitted, without thinking, that it was not inconsistent with the law of AGUILONIUS; but very little reflection will show that both cannot be maintained together; for corresponding lines of visible direction, that is, lines terminating in corresponding points of the two retinæ, cannot meet in the plane of the horopter unless the optic axes be parallel, and the plane be at an infinite distance before the eyes. Some of the modern German writers⁹ have inquired what is the curve in which objects appear single while the optic axes are directed to a given point, on the hypothesis that objects are seen single only when they fall on corresponding points of the two retinæ. An elegant proposition has resulted from their investigations, which I shall need no apology for introducing in this place, since it has not yet been mentioned in any English work.

R and L (fig. 26.) are the two eyes; C A, C’ A the optic axes converging to the point A; and C A B C’ is a circle drawn through the point of convergence A and the centres of visible direction C C’. If any point be taken in the circumference of this circle, and lines be drawn from it through the centres of the two eyes C C’, these lines will fall on corresponding points of the two retinæ D D’; for the angles A C B, A C’ B being equal, the angles D C E, D C’ E are also equal; therefore any point placed in the circumference of the circle C A B C’ will, according to the hypothesis, appear single while the optic axes are directed to A, or any other part in it.

I will mention two other properties of this binocular circle: 1st. The arc subtended by two points on its circumference contains double the number of degrees of the arc subtended by the pictures of these points on either retina, so that objects which occupy 180° of the supposed circle of single vision are painted on a portion of the retina extended over 90° only; for the angle D C E or D C’ E being at the centre, and the angle B C A or B C’ A at the circumference of a circle, this consequence follows. 2ndly. To whatever point of the circumference of the circle the optic axes be made to converge, they will form the same angle with each other; for the angles C A C’, C B C are equal.

In the eye itself, the centre of visible direction, or the point at which the principal rays cross each other, is, according to Dr. YOUNG and other eminent optical writers, at the same time the centre of the spherical surface of the retina, and that of the lesser spherical surface of the cornea; in the diagram (fig. 26.), to simplify the consideration of the problem, R and L represent only the circle of curvature of the bottom of the retina, but the reasoning is equally true in both cases.

The same reasons, founded on the experiments in this memoir, which disprove the theory of AGUILONIUS, induce me to reject the law of corresponding points as an accurate expression of the phenomena of single vision. According to the former, objects can appear single only in the plane of the horopter; according to the latter, only when they are in the circle of single vision; both positions are inconsistent with the binocular vision of objects in relief, the points of which they consist appearing single though they are at different distances before the eyes. I have already proved that the assumption made by all the maintainers of the theory of corresponding points, namely that the two pictures projected by any object in the retinæ are exactly similar, is quite contrary to fact in every case except that in which the optic axes are parallel.

GASSENDUS, PORTA, TACQUET and GALL maintained, that we see with only one eye at a time though both remain open, one according to them being relaxed and inattentive to objects while the other is upon the stretch. It is a sufficient refutation of this hypothesis, that we see an object double when one of the optic axes is displaced either by squinting or by pressure on the eye-ball with the finger; if we saw with only one eye, one object only should under such circumstances be seen. Again, in many cases which I have already explained, the simultaneous affection of the two retinæ excites a different idea in the mind to that consequent on either of the single impressions, the latter giving rise to the idea of a representation on a plane surface, the former to that of an object in relief; these things could not occur did we see with only one eye at a time.

Du TOUR¹⁰ held that though we might occasionally see at the same time with both eyes, yet the mind cannot be affected simultaneously by two corresponding points of the two images. He was led to this opinion by the curious facts alluded to in § 14. It would be difficult to disprove this conjecture by experiment; but all that the experiments adduced in its favour, and others relating to the disappearance of objects to one eye really proves, is, that the mind is inattentive to impressions made on one retina when it cannot combine the impressions on the two retinæ together so as to resemble the perception of some external objects; but they afford no ground whatever for supposing that the mind cannot under any circumstances attend to impressions made simultaneously on points of the two retinæ, when they harmonize with each other in suggesting to the mind the same idea.

A perfectly original theory has been recently advanced by M. LEHOT¹¹, who has endeavoured to prove, that instead of pictures on the retinæ, images of three dimensions are formed in the vitreous humour which we perceive by means of nervous filaments extended thence from the retina. This theory would account for the single appearance to both eyes of objects in relief, but it would be quite insufficient to explain why we perceive an object of three dimensions when two pictures of it are presented to the eyes; according to it, also, no difference should be perceived in the relief of objects when seen by one or both eyes, which is contrary to what really happens. The proofs, besides, that we perceive external objects by means of pictures on the retinæ are so numerous and convincing, that a contrary conjecture cannot be entertained for a moment. On this account it will suffice merely to mention two other theories which place the seat of vision in the vitreous humour. VALLEE¹², without denying the existence of pictures on the retina, has advocated that we see the relief of objects by means of anterior foci on the hyaloid membrane; and RASPAIL¹³ has developed at considerable length the strange hypothesis, that images are neither formed in the vitreous humour nor painted on the retina, but are immediately perceived at the focus of the lenticular system of which the eye is formed.

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§ 16.

It now remains to examine why two dissimilar pictures projected on the two retinaæ give rise to the perception of an object in relief. I will not attempt at present to give the complete solution of this question, which is far from being so easy as at a first glance it may appear to be, and is indeed one of great complexity. I shall in this place merely consider the most obvious explanations which might be offered, and show their insufficiency to explain the whole of the phenomena.

It may be supposed that we see but one point of an object distinctly at the same instant, the one namely to which the optic axes are directed, while all other points are seen so indistinctly, that the mind does not recognize them to be either single or double, and that the figure is appreciated by successively directing the point of convergence of the optic axes successively to a sufficient number of its points to enable us to judge accurately of its form.

That there is a degree of indistinctness in those parts of the field of view to which the eyes are not immediately directed, and which increases with the distance from that point, cannot be doubted, and it is also true that the objects thus obscurely seen are frequently doubled. It may be said, this indistinctness and duplicity is not attended to, because the eyes shifting continually from point to point, every part of the object is successively rendered distinct; and the perception of the object is not the consequence of a single glance, during which only a small part of it is seen distinctly, but is formed from a comparison of all the pictures successively seen while the eyes are changing from one point of the object to another.

All this is in some degree true; but were it entirely so, no appearance of relief should present itself when the eyes remain intently fixed on one point of a binocular image in the stereoscope. But on performing the experiment carefully, it will be found, provided the pictures do not extend too far beyond the centres of distinct vision, that the image is still seen single and in relief when this condition is fulfilled. Were the theory of corresponding points true, the appearance should be that of the superposition of the two drawings, to which, however, it has not the slightest similitude. The following experiment is equally decisive against this theory.

Draw two lines inclined towards each other, as in Plate XIX. fig. 10, on a sheet of paper, and having caused them to coincide by converging the optic axes to a point nearer than the paper; look intently on the upper end of the resultant line, without allowing the eyes to wander from it for a moment. The entire line will appear single and in its proper relief, and a pin or a piece of straight wire may without the least difficulty be made to coincide exactly in position with it; or, if while the optic axes continue to be directed to the upper and nearer end, the point of a pin be made to coincide with the lower and further end or with any intermediate point of the resultant line, the coincidence will remain exactly the same when the optic axes are moved and meet there. The eyes sometimes become fatigued, which causes the line to appear double at those parts to which the optic axes are not fixed, but in such case all appearance of relief vanishes.. The same experiment may be tried with more complex figures, but the pictures should not extend too far beyond the centres of the retinæ.

Another and a beautiful proof that the appearance of relief in binocular vision is an effect independent of the motions of the eyes, may be obtained by impressing on the retinal ocular spectra of the component figures. For this purpose the drawings should be formed of broad coloured lines on a ground of the complementary colour, for instance red lines on a green ground, and be viewed either in the stereoscope or in the apparatus, fig. 6, as the ordinary figures are, taking care, however, to fix the eyes only to a single point of the compound figure; the drawings must be strongly illuminated, and after a sufficient time has elapsed to impress the spectra on the retinæ, the eyes must be carefully covered to exclude all external light. A spectrum of the object in relief will then appear before the closed eyes. It is well known that a spectrum impressed on a single eye and seen in the dark, frequently alternately appears and disappears: these alternations do not correspond in the spectra impressed on the two retinæ, and hence a curious effect arises; sometimes the right-eye spectrum will be seen alone, sometimes that of the left eye, and at those moments when the two appear together, the binocular spectrum will present itself in bold relief. As in this case the pictures cannot shift their places on the retina in whatever manner the eyes be moved about, the optic axes can during the experiment only correspond with a single point of each.

When an object, or a part of an object, thus appears in relief while the optic axes are directed to a single binocular point, it is easy to see that each point of the figure that appears single is seen at the intersection of the two lines of visible direction in which it is seen by each eye separately, whether these lines of visible direction terminate at corresponding points of the two retinæ or not.

But if we were to infer the converse of this, viz. that every point of an object in relief is seen by a single glance at the intersection of the lines of visible direction in which it is seen by each eye singly, we should be in error. On this supposition, objects before or beyond the intersection of the optic axes should never appear double, and we have abundant evidence that they do. The determination of the points which shall appear single seems to depend in no small degree on previous knowledge of the form we are regarding. No doubt, some law or rule of vision may be discovered which shall include all the circumstances under which single vision by means of non-corresponding points occurs and is limited. I have made numerous experiments for the purpose of attaining this end, and have ascertained some of the conditions on which single and double vision depend, the consideration of which, however, must at present be deferred.

Sufficient, however, has been shown to prove that the laws of binocular visible position hitherto laid down are too restricted to be true. The law of Aguilonius assumes that objects in the plane of the horopter are alone seen single; and the law of corresponding points carried to its necessary consequences, though these consequences were unforeseen by its first advocates, many of whom thought that it was consistent with the law of Aguilonius, leads to the conclusion that no object appears single unless it is seen in a circle passing through the centres of visible direction in each eye and the point of convergence of the optic axes. Both of these are inconsistent with the single vision of objects whose points lie out of the plane in one case and the circle in the other; and that objects do appear single under circumstances that cannot be explained by these laws, has, I think, been placed beyond doubt by the experiments I have brought forward. Should it be hereafter proved, that all points in the plane or in the circle above mentioned are seen single, and from the great indistinctness of lateral images it will be difficult to give this proof, the law must be qualified by the admission that points out of them do not always appear double.   

(back to top)

1. See also a Treatise of Painting, p. 178. London, 1721; and Dr. SMITH’S Complete System of Optics, vol. ii. r. 244, where the passage is quoted. ↑
2. The luminous line seen by a single eye arises from the reflection of the light from each of the concentric circles produced in the operation of turning; when the plate is not large the arrangement of these successive reflections does not differ from a straight line. ↑
3. System of Optics, vol. ii. p. 388. and r. 526. ↑
4. “We see more exquisitely with one eye shut than with both, because the vital spirits thus unite themselves the more, and become the stronger: for we may find by looking in a glass whilst we shut one eye, that the pupil of the other dilates.” — Lord BACON’S Works, Sylva Sylvarum, art. Vision. ↑
5. BIRCH’S History, vol. ii. p. 348. ↑
6. Natural Magic, p. 100. ↑
7. Nouveau Système de Chimie Organique, 2me edit. t. 1. p. 333. ↑
8. Enquiry, Sect. xiii. ↑
9. Tortual, die Sinne des Menschen. Münster, 1827. Bartels, Beitrage zur Physiologie der Gesichtssinnes. Berlin, 1834. ↑
10. Act. Par. 1743. M. p. 334. ↑
11. Nouvelle Théorie de la Vision, Par. 1823. ↑
12. Traité de la Science du Dessein, Par. 1821, p. 270. ↑
13. Nouveau Système de Chimie Organique, t. 2. p. 329. ↑

Der Beitrag The birth of Stereoscopy: Wheatstone on Binocular Vision 1838, original source erschien zuerst auf the stereosite.

Alfred Silvester’s 1857 series of stereoviews entitled ‘Declaration of Love’ begins with a scene depicting a young woman seated at the piano in a smartly decorated room with elaborate wallpaper and plasterwork and what appears to be a fitted carpet, as opposed to the rugs on a wooden floor that you see in many Victorian interiors. The young woman is wearing an off-the-shoulder lacy top with a corseted waist, a full skirt and crinoline. A young man is standing close beside her, leaning over to turn the pages of her music. The door is open to the next room where a family can be seen sitting around a table, chatting and playing cards, while a little girl in her best party dress is peeping round the door, listening to the music and perhaps hoping to see what her sister and the young man are up to. It is a scene typical of the ‘Evenings at Home’ style also favoured by Silvester’s rival James Elliott, and the ‘Evening Music’ of the Gaudin Brothers, offering a glimpse into the lives of a prosperous upper middle class family.

A number of variants of the scene exist, with the camera in the same position but the figures positioned differently, allowing one to read a sequence into the events though, as they are not numbered, it is not clear whether that was intentional. I choose to place them as follows.

The young woman has finished playing her music and has risen to her feet. The young man seizes the opportunity and kneels at her feet, taking her hands in his and kissing them fervently, declaring his love. The little girl in the doorway is a witness.

In a variant of the scene, the little girl is not present so I imagine that she has gone next door to tell Papa that her sister has received a proposal.

In the final variant of the scene I have found to date, the young man is on his feet, still holding his beloved’s hand and looking imploringly in her direction while she moves towards the next room. Her expression is noncommittal but the little girl is smiling as are the people in the next room, so we trust that this declaration of love will meet with approval all round.

As the older reader knows, the male heart does not cease to beat faster in the presence of a beautiful young woman as we pass middle age, and Alfred Silvester used the same title ‘Declaration of Love’ for another set up showing a young woman at the piano but this time accompanied by an older gentleman with white hair, side whiskers and a receding hairline. He stands attentively beside her as she plays, holding her fan for her in one hand and a bouquet of flowers in the other.

In a variant of the scene, the young lady is standing, holding her fan and looking modestly away as the gentleman proffers the bouquet and declares his love for her. We do not know how she feels but her body language suggests that this proposal is not entirely welcome.

‘Declaration of Love’ is also the title of the following stereoview, presumably photographed on a separate occasion, as while the gentleman appears to be the same one, the young lady is dressed differently. They have moved away from the piano, which can be seen in the background, and the young lady is seated on a high backed chair while the gentleman kneels awkwardly beside her, pressing her hand to his lips. In this scene there is no doubt of her reaction as she turns away from him her hand raised to conceal the expression of amused disbelief. She clearly finds this proposal absurd and one hopes she has the kindness to let the old chap down lightly (and perhaps help him to his feet).

Under his pseudonym of ‘Phiz’, used at times of financial difficulty (he was a serial bankrupt), Silvester issued a variant of this scene entitled ‘May and December’ in which the (seated) old gentleman can again be seen declaring his love for a young woman whose likely response can be seen on the face she hides behind a fan. The ‘skeleton leaves’ we can see under a glass dome on the table beside him draw attention to his decrepit condition while the title clearly expresses the disparity of age between one in the Spring of their life and the other in its Winter. A more cruel title might be “No Fool Like an Old Fool’.

So, to any of you considering making a Declaration of Love this St Valentine’s Day, may this be a cautionary tale and I hope that your beloved is a worthy, and suitable, object of affection.

Der Beitrag A Declaration of Love erschien zuerst auf the stereosite.

Ladies and Gentlemen, please fasten your seatbelts because we are going to embark on a trip to the Underworld! This is a series of “Modern Diableries” inspired by the original French Tissue stereo cards. But what are those? French Tissues are a type of stereo card that, when viewed from the front, appear in plain black & white or sepia, like any standard stereo card. However, when illuminated from behind it magically shows brilliant colours and special effects, such as glowing red eyes through tiny pin-holes, and flames created with tiny cuts.

The Diableries, very popular in the 1860s (Habert and Hennetier were the most famous authors), depict life in Hell: from walking skeletons with glowing red eyes, to ghouls, and even the Devil himself! At the time of Napoleon III, these stereo views were a strong political and social tool bound to analyse and criticize the French society. And even if some scenes would look quite amusing, they would also hide a deep meaning behind it.

While most of the time the original Diableries were intended to be scary, my approach and interpretation on such Devilments is mostly cheerful and entertaining – we’ll see the skeletons dancing, having parties and taking on various adventures. The models for these stereos are not made from clay as in Victorian times, but tiny plastic skeletons paired with tiny props coming from a dollhouse shop. The background to such scenes is usually cardboard, adorned differently on each occasion.

DISCO INFERNO

This is what a dance floor would look like in Hell. The skeletons are dancing under the disco ball (a Christmas ornament) and they’re truly having the time of their after-life. 

JOYEUX HALLOWEEN

A Halloween-themed scene featuring a spooky pumpkin in the same style of the Diableries. If you look closely, you’ll notice one of them got so excited he even lost his head! 

LE CARNIVAL DES DIABLERIES

Carnival is a very popular holiday in Italy so I wanted to pay homage to it. The skeletons are wearing colourful masks and top hats I made from paper. 

LEÇON D’ASTRONOMIE

We’re attending an interesting lesson of astronomy; someone is raising his hand to ask a question. The crescent moon was made out of an old CD, and the stars in the background are rhinestones. 

MUSIQUE INFERNALE

A hellish concert is happening here, and the two stars are being applauded by a small audience. 

QUAND LA FÊTE EST FINIE

This is a New Year’s Eve party and the skeletons are quite drunk! A tiny bottle of champagne can be spotted amongst the confetti. 

THÉ EN APRÈS-MIDI

A fancy tea party in an exclusive club. These skeletons must be British! 

Der Beitrag A Trip to the Underworld erschien zuerst auf the stereosite.

One essential part of becoming a serious collector is frequent research from different online sources such as eBay, platforms of traditional auctioneers, etc. For further information, I recommend the article Collecting Stereoscopes by André Ruiter. Most often, you only find particular items or previous collections, but you never know where a specific viewer originally came from.

Thus said, there are some fortunate exceptions. One is the so called vide de grenier in France which means ‘emptying of the attic’. This can simply happen like a traditional flea market with items from one single household. Such sales are typically done by heirs after a bereavement. But the heirs could also hire a professional and the vide de grenier becomes a professional auction held on site — and nowadays sometimes streamed online.

That way, you will get a glimpse of the individual history of your treasure and know where it was stored, wether it was looked after or long forgotten, if the owner was well situated or not, etc. For me, these stories are invaluable and add a more personal aspect to a collectible. This counts even more because those stereoscopes will usually contain photos that tell even more about their past.

As a passionate restorer, I especially appreciate viewers that have remained untouched since their last use. I carefully remove the dust of decades to reveal the original beauty of a stereoscope. Being the first one to do so feels almost like getting in touch with those who bought it a century ago. I want to take you to one of those journeys.

A vide de grenier took place on September 30, 2021 in Abbeville in the north-west of France near the coast. As usually, you could take a look at the location online a few weeks in advance. Between furniture, knickknacks and rubbish — all tagged on with a little number — I spotted a tabletop stereoscope carelessly placed in a closet:

The large black knob on the site of the device identifies it as a revolving stereoscope (for additional information on this type see the article A Multiview Stereoscope Comparison). Furthermore, the little keyhole and the and the indistinct horizontal line above tell that you can flip back the top to replace the whole chain. Indeed, on the left of the viewer you can see a second chain including stereo photos. I easily recalled the model. This type of viewer was only manufactured by Mattey both for the 8.5x17 and the 6x13 format. If you used card board frames it was also suitable for the 45x107 format introduced by Jules Richard in 1893 (for background information see the article Le Taxiphote). Once again, André Ruiter has written an interesting article about exactly this type, the Mattey Revolving Stereoscope. While he has one of the rare deluxe models, this one is the more common mahogany standard version. Nonetheless, the exchangeable chain makes it one of the more advanced viewers of that time.

So, I subscribed to the auction and logged in live at September 30. As you may have already guessed, I won it for a good price, and after the normal process I received the stereoscope a few weeks later.

According to my request, they had removed the chain to prevent unwanted movement during the transport. So I was not able to tell which series of stereo photos was inside the viewer most recently. One consisted of family and travel photos, one of a mix of professional and amateur slides depicting the first World War. What I could tell was that the latter was used a lot more frequently — the black paint on the right turning knob was almost completely worn down. Also, this one is the original chain that came with the viewer. Both bear the serial number 1213. The additional chain has the number 1220. So I can assume that it was bought at the same time or only slightly later.

Mattey produced this viewer model for quite a long time without any remarkable changes. So how can I tell if my viewer is an early model from shortly before 1900 or a late model from around 1920? As far as I know there is no reference to the serial numbers and a low four digit number is neither definitely earlier nor later.

Luckily, restoration always requires a really close look. The smaller turning knobs that let you adjust the oculars are made of wood and have a narrow notch. Actually, that notch is the reason why I am familiar with this kind of knob: it’s terribly annoying to clean it perfectly. It seems that most manufacturers, despite all competition, used the same focusing knobs. That’s why I’ve come across this type many times. But only on early viewers! They all seem to have changed to bakelite knobs at some point. More precisely, Richard already started to use bakelite knobs with the introduction of the Stéréo-Classeur in 1900, while the chain-operated predecessor still used these wooden knobs.

Another piece of evidence is that my similar 8.5x17 Mattey viewer has also wooden knobs and bears the serial number 891 which is only a little earlier than 1213. On the other hand, two later Mattey models have also changed to bakelite knobs but it seems that Mattey discontinued using serial numbers so this reference is unavailable. Nevertheless, it seems reasonable for me to conclude that I got an early model from around 1900.

After this little digression about dating the viewer, let’s return and take a closer look. Did I say that I enjoy removing dust from an untouched viewer? I have to clarify that I was talking about gently blowing or wiping it of. This time it would be hard work.

This viewer was extraordinary dirty and made me doubt if I could reach a satisfying result. There was some sort of grey powder everywhere, even on the inside and on every single stereo photo. So I did a cleaning of the outside with a damp sponge before I tried to disassemble as much parts as possible.

I then applied a water based liquid including abrasives that sanded off the remaining dirt and smoothed the shellac. For a more detailed description see my article about Restoring Stereoscopic Antiques. I had already seen that there was a flaw in the top trim, but with the dirt gone I discovered even more scratches especially on the top, but also here and there on the base. Fortunately, front, back and the sides were not affected at all. Still, before I could do the finishing I would have to do an additional step.

Whether you use shellac, oil or wax, each will change the color of the wood in different ways. For that reason, you may indeed apply different layers one after another, but you have to build up the surface the same way on every part. In this case, a thin layer of linseed oil varnish would bring back the typical shine on polished shellac. But if there’s a scratch down to the wood oil will penetrate through it and this part of the wood would become much darker than the surrounding areas. I like visible scratches as a part of the patina, but they don’t need to be highlighted. To prevent that from happening, I would need to retouch the scratches with shellac first. I only dabbed a little bit of shellac into the scratches with a cotton swab and repeated the treatment with the polishing liquid. I finished the wood working with a layer of shellac on the trims because these parts are generally worn and I wanted to bring back an overall shiny effect.

Even though I think that the handles were originally burnished and not brass colored I had to grind them off with steel wool to remove all signs of corrosion and make them shine again. By leaving out the deeper lying areas I still achieved a nice antique effect.

I also used my polishing liquid for the black painted metal oculars and steel wool for screw heads, etc. Finally, I put on a thin layer of linseed oil varnish on all wooden or painted parts and penetrating oil on metal parts to protect them from further corrosion. I also cleaned the inside and the chain with a soft brush and applied only a little linseed oil varnish to increase the saturation of the black paint. A little oil on all moving parts and that’s it.

I think it was good that the stereoscope was hidden in a closet and the sun could not bleach the wood. Though, if you have a stereoscope that looks pale on the side that stood towards a window for years, this is not always problem. For example, if you have a waxed surface you can simply wash it off. After you applied oil to the wood the color will mostly come back. But this is always a problem with shellac. Oil can not penetrate the wood through it and you don’t want to remove the original shellac because you will always be able to distinguish between old and new shellac. But that’s another story.

So, overall I’m really happy how it turned out and I hope you enjoyed this time travel back to the original look of this stereoscope as much as I did during the process. Yes, this is really the same viewer.

After this resurrection, it was, of course, not difficult to find a nice place on my shelf, where it is surrounded by comrades made by Richard, Bize, Zeiss and others.

Der Beitrag A Restorer’s Journey erschien zuerst auf the stereosite.

What kind of entertainment would you have as a Soviet kid growing up in the 1980s? A couple of dolls, clothes, and rags for the dolls’ dresses; metallic constructor sets, the vinyl recordings of children’s stories; some cassettes with popular Russian songs, and a bunch of filmstrips (a 35 mm film with still images and captions to be projected on a wall – no movement or sound!). These things were in almost everyone’s possession – at least, that’s how I remember my friend’s toys. However, I had something very special – a set of stereo cards, along with a simple stereoscope that looked like binoculars. 

Of course, back then I knew nothing about stereoscopy, as well as the story behind those slides, other than the fact that they were produced in East Germany.  Each card featured six stereo pairs, and to view them, you had to slide it into a viewer, and go from bottom to top – from the beginning to the end of a particular story. In my early years I had only two cards. However later my little collection grew, and eventually I ended up having 14 sets of stereo slide cards. Many of them were Brothers Grimm tales (Snow White, Rumpelstiltskin, Hansel and Gretel, Little Red Riding Hood, etc.); I also had a series featuring Teddy Bears and their adventures – how they go to school, hike, exercise, climb mountains, or even go to space! Out of the whole collection, I loved the Teddies slides most of all, and in a way, they influenced my own tastes and likes. Space Teddies made me fall in love with the sci-fi stories; the card showing them climbing mountains made me dream about the distant places I have never seen. And in general, these cards broadened my imagination. We all know that many chidren created their own imaginary worlds. Thanks to these stereo images, mine were almost tangible. 

For many years, these cards remained my only exposure to stereoscopy. I had no idea that it existed beyond this format. Of course, after I started taking my own stereos, I realized that these slides were popular around the world, as a part of more global process. I learned that people from outside of the Soviet Union (and the Eastern Bloc countries) are rarely aware of these East German stereo slides.

In the rest of the world everyone knows the View-Master Reels. After doing some research on my cards, I found out that my stereo viewer, named Stereomat, was produced in Kamenz (East Germany) in the 1970s. Organized into thematic series, each of the cards had a code marking a certain subject (for example, TS ‘Teddie Serie’ for Teddy Bears stereos, ZS ‘Zoo Serie’ for the stereo photos of animals, MS ‘Märchen Serie’ for the fairy tales, etc.). 

According to one of Russian collectors (https://cccp.livejournal.com/24777.html), TS and MS series circulated widely in the Soviet Union, while others were less well-known. My collection consisted almost entirely of these series, with the exception of one ZS card. This was actually one of the first cards I had ever had, with the stereo images of animals from the Berlin Zoo. You can see that these slides were viewed (and handled) by a little kid, and therefore, their quality is not the best. 

Another card from my initial set featured a story of a naughty mouse, who, after stealing a piece of ham, is chased, and eventually captured by his buddy. This example demonstrates how elaborate these stereos were! Now, as a stereo enthusiast, I can see how well the sense of depth was used, and how interesting and original the settings of this story were. 

Interestingly, when I got more stereo slides as a gift several years later, I found another card that evidently told the same story, only this time, the little thief manages to escape. However, his greediness is punished by an upset stomach, and the story culminates in more didactic ending. 

The Brothers Grimm tales were extremely popular among Russian kids, and therefore, immediately recognizable.  No wonder that this series was extensively represented in my personal collection! I would like to share a couple of stereo pairs from Rumpelstiltskin, the story of a miller’s daughter that became a queen, a vicious gnome whose name nobody can guess, and an evil deal.

I also have a card that does not really match any of the categories. It is about a day in the life of a driving school’s students and instructors, starting from the moment that they come to the class, to the moment when they pass their tests. My guess is that, since this card is from the MS series, it is probably based on a children’s story or an animation film. Unfortunately, I could not find the source of these slides. 

Finally, here are my most favorite cards, featuring the adventures of Teddy Bears (the TS series). Again, I do not know if this series was written and staged specifically for the stereo slides, or the creators based it on some existing stories. I think that these are breathtaking examples of how masterful the Stereomat team was. From the carefully designed settings to the use of depth, from the cute and lovable teddies to the amazing lighting. Back then, when I was a kid, I firmly believed that these beautiful scenes indeed existed somewhere across the sea, and my dream was to climb these mountains, and maybe even go into space one day. 

Der Beitrag My Magic Cards erschien zuerst auf the stereosite.

Despite the fact that my field of work is experimental Stereographic Art, I am recording and documenting in 3D wherever I go, such as Galleries and Museums, and especially, when a Monumental Installation by an Interdisciplinary artist, or artists takes place. However, I have discovered that 3D can capture and retain a sense of the physical and  geographic  experience of being immersed in such a massive art exhibit, better than traditional 2D recordings. These Monumental Installations can typically take up a city block or more in size, but are unavoidably and tragically impermanent. Fellow participants are an important element of these enormous installations, and their presence and interaction with the piece can also  be captured without disruption by using a pair of small, hand-held cameras for recording in 3D.

Because different people have different experiences, I try to return to the piece and shift my focus and sense of awe to different aspects of the piece so that an edited version can provide a cumulative impression while also capturing the differences that an ever-changing presence of fellow visitors produces. Both of the featured 5‑minute long 3D videos have an informal intro, with occasional text  pages that give the viewer information and insights as the video progresses. This, I feel, helps the viewer settle in and immerse themselves in the  3D rending of the  artwork, as well placing them among the other participants engaging in the piece. Although these present recordings are relatively casual, I believe that more extended 3D coverage and production would help to preserve these one-of-a-kind experiences for future generations (to some extent).

Der Beitrag Bright loose images for the Monumental Art series erschien zuerst auf the stereosite.

It’s probably safe to assume that most people were introduced to 3D images via View-Master. Introduced at the 1939 New York World’s Fair, the handheld 3D viewer was a very popular format that sold literally billions of products from the 1940s right on through the 2000s. Here you’ll find a brief history of View-Master, some images from my collection and key content categories that may be of interest to those looking to start or grow their collections. 

View-Master was invented by William Gruber in the 1930s, working with Sawyer’s Inc of Portland, Oregon. Sawyers was then called Sawyer’s Photo Finishing Service and was one of the world’s largest producers of scenic postcards. 

The View-Master was introduced at the 1939 New York World’s Fair, just a couple of years after the invention of Kodachrome film. View-Master used Kodachrome exclusively until the late 1970s, and because of this, the vast majority of View-master transparencies retain their color and vibrancy over time. 

View-Master was originally marketed as an exciting alternative to scenic postcards. The reels were most often sold at photography stores, gift shops at scenic attractions, and via mail order. When I first started collecting, that era was my primary focus. It gave me the opportunity to view these little time capsules, to take a quick vacation to the past.

As my collection grew, so, too did the geographic span of images. View-Master was truly trying to capture photos from every corner of the globe they could get to. There are many reels of far-flung festivals and lots of artisans and people at work, including a man carving ivory in Hong Kong, a woman making filigree silver jewelry in Yucatan, Mexico, a man carving a boat in Panama. There are photos from life on every continent and most major cities, even Russia during the cold war. 

There are also many U.S. communities of people represented including Native Americans, Creole and Gullah. Globally, there are groups of people and even entire places that no longer exist. There’s an entire packet dedicated to Zuiderzee, a fishing village in The Netherlands that existed before they built the dams that put the city under water. 

I’ve learned a lot about the world and the past through View-Master. And that’s by design.

William Gruber and the folks at Sawyer’s truly believed in this product as an educational tool. There are many examples of educational reels over the years. Notably, in the 1940s, the U.S. military purchased around 100k viewers and several million reels. From range estimators to in-air identification, these tools were used in training. Other educational reels produced included mushroom identification, flower identification, a sweeping history of Chinese art and medical reels dedicated to body dissection.

The educational reels overlap with another key component of Saywer’s View-Master business that was there from the beginning: the production of commissioned commercial reels. Commercial reels sold just about anything you could name, from bourbon to toothpaste to farm animals. Movie preview reels are some of the most sought-after by collectors. They were used exclusively in movie theaters as a way to promote upcoming movies during the 3D movie craze of the 1950s. 

Also in the 1950s, Sawyer’s purchased Tru-Vue, the company’s main competitor. While this wiped out the competition, it also captured the licensing rights to Walt Disney Studios. Four years later, Disneyland would open, and the rest is history. It was a wildly successful partnership for both brands that spanned many decades. There in many who just collect View-Master’s Disney items and that’s probably enough to keep a person busy for years. 

Another area for collectors and a big thing for Sawyer’s in the 1950s, involved their end-to-end service for personal reels. They sold a View-Master personal stereo camera, film cutter and mounting supplies. The even sold a 3D projector called the Stereo-Matic 500 that required a silver screen and polarized glasses. A budding photographer could do everything themselves from start to finish, but if you didn’t want to make your own reels, the fine folks at Sawyer’s would do it for you via their mail-in service. 

The Toy Shelf

Most people associate View-Master with cartoons and pop culture. And that’s partly because, in the 1960s, GAF Corporation purchased View-Master. They leaned heavily into pop culture and kids reels. And, while they saw success, by the late 1970s, cost cutting measures led to GAF switching to lesser film stocks and quality overall dropped. View-Master changed hands a couple more times but by the late 1990s was owned by Mattel and nestled under the Fisher-Price brand, placing it firmly in the preschooler toy aisle. 

While that outcome is a bummer for those who don’t care about cartoons and other kids programming, one neat thing about VM is that it’s from literally everyone’s childhood. Any viewer can show you any reel, from 1939 on. So, everybody — from grandma to a modern preschooler — enjoyed the same tactile experience. 

There’s something profound in these shared childhood touchpoints. 

Many collectors start out by acquiring things they had and loved in childhood. If you were a kid in the 1960s, you might want the Monkees set; in the 1970s, Eight is Enough; in the 1980s, Knight Rider. If you love sci-fi, there’s everything from a visually stunning Twenty Thousand Leagues Under the Sea diorama set to scenes from the set of Dune in 1984. Numerous space-race and NASA-themed reels exist. And many major pop culture franchises are represented including Marvel, Indiana Jones, Jurassic Park and Harry Potter. 

In terms of reels directed at children, it seems the diorama reels in particular hold a special place in the hearts of collectors. The scenes created by Florence Thomas, Joe Liptak and other sculptors who worked at View-Master has had a lasting impact. I know this because I started an Instagram account in the fall of 2020 to share images from my View-Master collection, and I was happily surprised to find so many people who love View-Master. Many of my followers are themselves artists — cartoonists, illustrators, puppeteers and painters — who have told me that View-Master serves as inspiration in their own work today. It’s not hard to understand why.

The sculptors did incredible work, and the diorama reels are well worth seeking out. And those of you with an interest in stereoscopic photography should definitely check them out. The tabletop 3D photography produced for these reels is unparalleled. 

Semiotics — Who’s Here and Who’s Not

Of course, it would be ridiculous to not mention that the past is a decidedly problematic place.

With a degree in film studies, I can’t help but think about the meanings and symbols found in compelling images from the past. What did the images say to people at the time? Who did they include? And, sometimes, more importantly, who did they leave out? 

Erasure is probably the neatest trick VM ever pulled — it’s something that the dominant cultural narrative excels at. Black adult Americans are often absent from reels though smiling children are represented semi-regularly. The state tour packets often include a few surprises and regular people of all races and classes working regular jobs. Many of the reels produced by the View-Master factory in Belgium include incredible glimpses into places it would be difficult to see otherwise, from cheese being made at an abbey in the 1940s in Switzerland to how tea was made in India in the 1950s. The educational components and the desire to share images from every corner of the globe was sincere at Sawyer’s, and I find the farther from home I get in View-Master reels, the more I learn. 

And, for me, that’s one of the key elements of collecting: The thrill of discovery. While I love to see places and people I would otherwise never see, there’s a special place in my heart for the weirder stuff. 

I enjoy images of tourists traps, of festivals and kitschy events — like drunken revelers at Mardi Gras or Rio’s Carnival in the 1940s. 

A few more weird things I’ve found and loved: There are two entire commercial reels dedicated to Hereford Ranch’s Heifer sale of 1953. Each cow looks alike unless you know something about buying livestock. 

The Paris packet is fantastic and includes this image with the caption “tramps live under the bridges of Paris.” I just don’t think they ever would have included such an image in a reel about the United States. 

A bizarre FBI packet features a made-up kidnapping plot but takes place at the real FBI headquarters and feautres a 3D photo of J. Edgar Hoover. 

And even though kids reels are somewhat outside my wheelhouse, there are many fun ones to be found. I just recently discovered these creepy-hilarious Hugga Bunch reels from 1985. 

This is just the tip of the iceberg when it comes to View-Master content categories. One of the best things about View-Master is that it covered so many subjects that, as my personal interests have evolved, so, too, has my collection. 

Der Beitrag Nostalgia, Semiotics & Weird Stuff: A Guide to Collecting View-Master erschien zuerst auf the stereosite.

Jules Richard and the Verascope

Jules Richard took over his father’s precision instrument company in the late 19th century and patented a stereo camera called the Verascope in 1893. The name is derived from the antique Goddess of truth Veritas and the Greek word σκοπός (watcher). This neologism refers to the separation of the camera lenses, which is just about the average human eye spacing. 

The camera itself was also a high precision instrument. It was entirely made of metal to prevent humidity and temperature from affecting its operation. But most important, it used a new image format, 45x107mm, which was much smaller than the two common stereo formats of that time – and so was the camera, too.

Despite a widespread interest in stereoscopy, the smaller size was probably the required spark that ignited the boom in amateur stereo photography.

In addition to handheld viewers, Richard also manufactured revolving stereoscopes for glass slides in the new format. These viewers were all simply labeled Stéréoscope, vues prises avec le Verascope (Stereoscope for views taken with the Verascope). Verascope became a synonym for amateur stereo cameras.

Even today, stereo cameras and stereoscopes in the French local advertisements are still titled Verascope and Taxiphote sometimes, even if they were made by other manufacturers.

The revolving stereoscope had one large drawback: changing the slides is extremely annoying and so you would only have access to a limited selection of your photos in the end. And while the Verascope is a high precision device, flipping the glass slide through your field of vision is rather simple and the viewing experience is not as good as with a handheld viewer.

Stéréo-Classeur

But in 1899 Richard and his technician Louis Colardeau patented a new system that allowed the use of bakelite magazines containing 25 slides each. The dimensions of that stereoscope were the same as the common tabletop viewers, but instead of 50 views, it could hold up to 300 views in drawers underneath the mechanism.

They simply called it Stéréo-Classeur (stereo cabinet), and it was offered in their catalogue in 1900, unspectacularly besides the various revolving stereoscopes. This would change soon after.

Le Taxiphote

I believe that the Stéréo-Classeur was planned as a test run. The viewer was renamed to Taxiphote one or two years later – without any changes of the mechanism. From then on there would be an update or extension of the Taxiphote family every year, widely promoted through advertisements.

If you thought the Taxiphote has anything to do with the vehicle, you’re wrong. The name is again derived from ancient Greek: the first part comes from τᾰ́ξῐς (arrangement/ordering) and the second from φῶς (light). In fact, this is quite close to the former name Stéréo-Classeur.

It’s time to take a closer look.

In most cases, the standard Taxiphote, later called Taxiphote foyer moyen (long focus), consists of a storage base and an upper part housing the mechanism, just like the Stéréo-Classeur before. After placing the magazine on a carrier, a lever on the right operates two metal arms below the carrier that push the individual slides to the ocular level for viewing. These two metal arms need to move very precisely to prevent scratching the neighboring slides. When the slide is brought back into the magazine the carrier is moved backwards so that the metal arms access the next slide. This horizontal movement is connected to a counter on the left side of the Taxiphote. If you hold down the main operating lever you can turn the knob on the counter and navigate directly to a specific slide in the magazine.

The new Verascope slides all had some blank space in between the two single images. This area was commonly used to record information about the stereo photo, like place and date. Another lever on the left of the Taxiphote tilts down an additional lens and mirror system that enables viewing that space with your right eye.

Finally, like all better stereo viewers, the Taxiphote also has adjustable focus.

In addition to viewing photos, a 1902 advertisement tells us about a lantern attachment that could be used for projection over distances of up to 4m. The combination of lantern attachment and Taxiphote resulted in a huge apparatus that allowed only monoscopic, and not stereo, projection. In 1923, the projection unit was substantially reduced in size, and in 1927, anaglyph 3D projection was introduced.

In 1903, an employee of the Richard company wrote to a photography reseller that the Taxiphote would also be available for the 6x13 and 8,5x17 formats. One year later, Richard introduced another new format upon suggestion of the members of the Stéréoclub Français. This 7x13 format was said to be the most rational stereo format for several reasons.

These four formats were continuously produced even though the storage space in the base varied. In most catalogues the names are as follows:

• Taxiphote normal / foyer ordinaire / foyer moyen for 45x107
• Taxiphote no. 1 for 7x13
• Taxiphote no. 1bis for 6x13
• Taxiphote no. 2 for 8,5x17

Also in 1904, Richard patented a new feature for all models. From now on, the two oculars were placed on two wooden plates that allowed interocular adjustment to suit the eye spacing of the individual person.

If the label on your device already bears the Taxiphote name but the interocular distance can’t be changed, then your unit was presumably made between 1900 and 1903.

Le Taxiphote court foyer

It goes without saying that the distance between the lenses and the slide has to be at least the width of a magazine, which is almost 10cm. This is no problem for the larger formats, but when viewing Verascope slides, it feels like you were standing in a dark room with a small window, because large areas of your field of vision are just black space. 

This seems to have bothered Richard several years. In my opinion, this was possibly the most challenging task in the development of the Taxiphote. It would take five patented attempts finally resulting in two different solutions.

Modèle mécanique

There were several handheld Richard viewers that had less distance between the slide and the lenses. This court foyer (short focus) provided a superior viewing experience, whereas 45x107 slides still looked just like 6x13. Richard wanted to make that possible for the Taxiphote as well. In 1905, two patents show mechanisms that carried the individual slide both vertically from the magazine to the ocular level, and afterwards also horizontally towards the lenses. A catalogue proves that this so called modèle mécanique was sold in 1909, but it is rarely seen. Probably the mechanism was not perfected yet – this would take a few more years.

Modèle optique

The more commonly used method was the so called modèle optique, which took a completely different approach. Instead of a horizontal movement, it used additional block lenses to magnify the photo.

These lenses could be either permanently lowered in front of the oculars or manually by another lever on the left. Using lenses for that purpose leads to some distortion at the edge of the image, but overall, the viewing experience is quite satisfying, especially if you were annoyed by the black space around the image. On the other hand, you had to pay quite a high price, because the stereo photo was cropped. Not much, but sometimes you were going to miss details in the corners.

Modèle simplifié

Starting at 250 francs the average price for a Taxiphote would be around 300 francs. In 1908 Richard introduced a new version only for the Verascope format at a price of 148 francs. The so called Modèle simplifié (simplified model) had a crank operated mechanism instead of a lever, and is very comfortable to use. In fact, you can easily move back and forwards just by turning the crank the other way around. 

There was still a counter on the left with another extremely clever improvement. While you need to hold down the lever of the other Taxiphote models to freely navigate through the inserted magazine, you now just needed to push the knob before turning. The crank operating system was probably the key for the further development of the modèle mécanique.

Still, this model was cheap overall. No storage base, no profiled corners, poor construction for reading slide titles, etc. In the cheapest version, the adjustable interocular distance was also missing. The simplified product line was continuously produced though. A 6x13 version appeared in 1926, and in 1931 the wooden body was enlarged for a more comfortable viewing height and a storage base was added.

Meanwhile, an electric lamp attachment clair soleil was patented in 1909 for all formats and the wooden ocular plates were replaced by adjustable eyepieces entirely made of metal, patented in 1911. The latter are a good hint for dating Taxiphotes, because the serial numbers hardly provide reliable information.

Taxiphote court foyer, modèle mécanique – Part 2

Even though the modèle mécanique was already available, it seems likely that Richard changed the mechanism. This is extraordinary especially because the mechanism wasn’t changed in any of the other models, except the addition of new features.

But in 1911, there are two more patents on the modèle mécanique. It seems to me that this new mechanism was introduced another two years later in 1913 because the price suddenly jumped, while the prices for the other models remained the same. Indeed, it’s worth it!

The mechanism is now driven by a crank, just like the modèle simplifié. One turn to lift the slide and another turn to move it towards the oculars. No cropping of the image, no distortion. The viewing experience is fantastic. In my opinion this is really the best Taxiphote ever produced.

It takes also advantage of the push-and-turn mechanism of the simplified model to navigate through the slides. The lens and mirror system for reading the slide title is now lowered by pulling a chain on the left. I think this looks a little weird and unstable compared to the former lever mechanism but it works very well.

Autochromes and the Taxiphote

Because of the success of color photography achieved with Autochrome slides, many manufacturers like Gaumont, Plocq or Hemdé offered special magazines to handle Autochrome slides. This was necessary because Autochromes were developed as direct positives and there was no possibility for inverting the left and right images, except by cutting the glass and switching the positions. Therefore, a second glass was typically added for stabilization and protection because autochromes were extremely prone to humidity. So, the slides were twice as thick as normal slides. This is the reason why different magazines were required.

Richard went a more sophisticated way. Instead of cutting Autochromes he recommended turning the slides upside down (because this switches the left and right images as well!) and then attaching prisms on the oculars to invert the image. These so called Redresseurs became available 1913 as well.

Because Autochromes were expensive and difficult to develop, a stereo photo collection would typically consist of mostly black and white photos, with just a few color images. Switching the Taxiphote from viewing black and white to color thus meant manually exchanging the oculars from time to time. Unfortunately, this would take a few moments each time.

This leads to the last addition for the Taxiphote modèle mécanique: A quick exchange mechanism for the entire eyepiece assembly together with two additional sets in a high-quality leather case. One set for Autochrome lenses, and one set to change the short focus back to the long focus– for whatever reason.

Further developments

In 1923, additional magnifying lenses were available also for the 6x13 and 7x13 Taxiphotes. These had the same short focus effect as the modèle optique.

As mentioned above there was a smaller design for the projection lantern in 1923 as well as an extension and a redesign of the simplified model in 1926 and 1931. Also, in 1927 anaglyph projection units became available. The 8,5x17 model disappeared in 1930.

But, we can conclude that all important developments were finished by 1915 and all models were in continuous production until the 30’s. With the introduction of the Verascope F40, the era of the multi-slide-viewers ended.

Deluxe versions and furniture

To arouse interest there were also specially designed deluxe versions of the Taxiphote that were not always available according to catalogues.

For those who had larger photo collections, there were storage cabinets especially designed for the Taxiphote and produced by Richard. You could also buy just the drawers and incorporate them into other pieces of furniture to suit your purpose.

Conclusion

The Verascope and the Taxiphote are two halves of an unbelievable stereo development effort that went on for 40 years essentially without any changes. The Taxiphote was exported to and patented in many countries. All this serves as an example of how attractive stereoscopy was at that time, and also confirms the quality of the Taxiphotes as a technical device. We can only guess at the prestige of having a Taxiphote at that time. 

But what would better illustrate the meaning of the Taxiphote to its owners than the Autochrome stereo photo Thomas Asch found in one of his devices?

If not otherwise stated all pictures show pieces of my personal collection. I’m thankful that Sébastien Lemagnen from antiq-photo.com provided me with some photos as well as Thomas Asch and Paul Burford.

Der Beitrag Le Taxiphote — the most famous French stereo viewer erschien zuerst auf the stereosite.

At a recent meeting of the VSC, someone asked if there are stereo views of true crime. I’m not a big true crime fan or a stereo scholar, but this seemed like a fun pandemic online research project. What is meant by true crime? It’s a nonfiction genre having to do with actual crimes, usually murder. It’s popular now, but it was popular in the 19th century too‒just think of the penny press and the National Police Gazette. As the joke says, “Crime may not pay, but it sells!”. I was curious to see if it made its way into stereo cards, too.

Almost all the material I found was for Americans. The images you’ll see come only from online sources, mostly the Library of Congress and the New York Public Library. I had never heard of any of these murderers, but amazingly, two of them have their own Wikipedia articles and I was easily able to find some material on the rest also. Conversely, I was unable to find material connected to some murderers who are still household names in the U.S., like Lizzie Borden or Alferd G. Packer.

In what follows, I’ve tried to provide a thumbnail sketch of each crime. Accounts from the time often vary, so I’ve tried to present a composite set of the facts which I think are the most likely.

Please note: Most of these stereos are G‑rated, but there are a few which may be disturbing to some people. Specifically, there are two hangings (both shown before the trapdoor opened) and one dead body. Also some of the descriptions of the crimes may be disturbing. These are images of murder and capital punishment, and they’re not pretty.

Assassinations

The first thing that comes to mind for true crime in stereo was Eadweard Muybridge, but more about him later. The second thing was the assassinations of three US presidents: Abraham Lincoln in 1865, James Garfield in 1881, and William McKinley in 1901. This stereo memorializes all 3, in true maudlin turn-of-the-century style, but with great stereoscopic depth!

Lincoln Assassination

This is the only stereo I could find of John Wilkes Booth, who shot Lincoln. It’s an accidental stereo, assembled by John J. Richter from two carte-de-visite images where Booth moved a little between exposures. As a result, the depth is a bit exaggerated.

On April 26, 1865, Boston Corbett’s regiment had surrounded Booth and one of his accomplices in a tobacco shed in Virginia. They were under orders to take Booth alive, but somebody shot him anyway. There are doubts about whether it was Corbett, but he took the credit (or blame). He was to have been court-marshalled, but the Secretary of War intervened.

The assassination of Lincoln was part of a broader conspiracy. Booth isn’t in this photo, having already been killed. The hanged were: David Herold, who helped Booth escape, Lewis Powell, who tried to kill Secretary of War Seward, George Azterodt, who was supposed to kill Vice President Andrew Johnson but lost his nerve, and Mary Surratt, who owned the boarding house where the conspirators met, and who was the first woman to be executed by the U.S. government.

Garfield Assassination

This is the old DC jail where Charles Guiteau, who shot President James Garfield, was held and eventually hanged. While he was held here, two attempts were made to shoot Guiteau, including one by one of his guards. People took up a collection for the guard‒that’s how popular Guiteau was.

It took Garfield almost 3 months to die after being shot, so in court Guiteau claimed, “The doctors killed Garfield ‒ I just shot him!”. He’s usually described as a “disappointed office seeker”, but I don’t think that fully captures his weirdness. He literally danced to the gallows, and then recited a poem he had written, titled, I am going to the Lordy. Both he and Booth are characters in the musical Assassins by Stephen Sondheim and John Weidman, parts of which are available on YouTube.

Plain Old Murders

Gaius Jenkins, Lawrence, Kansas Territory, 1858

There was a plenty of shooting in Kansas Territory in 1858 (the photo was taken some years later), over whether the state-to-be would have legal slavery. In this case, though, both men were Free Staters. What they couldn’t agree on was the ownership of a certain piece of land in Lawrence, including the well you see here (the wellhouse is at the far left).

On June 3, 1858, Gaius Jenkins, carrying a revolver, came to get water from the well which both he and Jim Lane claimed. Lane met him with a shotgun. A man with Jenkins shot Lane in the leg, and Lane shot and killed Jenkins. Lane was acquitted at trial and went on to become one of the two first U.S. Senators from Kansas, and overlapping his Senate service, a Union Civil War general, trading atrocities with the Confederates on the Kanas/Missouri border. In 1866 he became depressed and committed suicide.

Thomas Brown and Wife, Hampton Falls, New Hampshire, 1868

Josiah L. Pike murdered Thomas Brown and his wife, a couple in their 70’s, at Hampton Falls, New Hampshire, on May 8, 1868, with an axe. He stole $500 and an overcoat. He doesn’t look at all sorry in this photo. I haven’t found Mrs. Brown’s name mentioned anywhere, so far. A local church group seems to have been determined to save Pike’s soul by showering him with love, and they held his hand, brought him flowers, and had a choir sing to him. Mark Twain, disgusted by this, wrote a short but very snarky essay called Lionizing Murderers.

Jonathan Lunger and Marie Lunger, Ulysses, New York, 1870

You are looking at the remains of a cabin near Ulysses, New York, which was burned to the ground on March 20, 1870. Two bodies, almost completely reduced to ashes, were found inside.

Jonathan Lunger and his daughter had been awakened by a sharp noise. Lunger found his arm covered in his wife Marie’s blood, and standing over her, holding an axe, was Mike Ferguson, a man who hung around near his cabin and whom he sometimes hired. After a short conversation, Ferguson stove in Lunger’s skull with the axe. Ferguson took Lunger’s watch and rifle and their little money and burned the cabin to the ground. He forced 14-year-old Anna to come with him.

Ferguson was caught and Anna was freed and testified at the trial. Ferguson was hanged at Ithaca in 1871. His motive for the crime was never clear.

Georgiana Lovering, Northwood, New Hampshire, 1872

Franklin B. Evans had set some snares for the birds in the woods outside Northwood, New Hampshire. On September 25 of 1872, he asked his 14-year-old niece, Georgiana Lovering, to check his snares, claiming that he had to work. He hid, then followed her into the forest, then raped her, strangled her, and extensively mutilated her body with a knife.

Evans came up with a couple of stories about a mysterious stranger who had run off with the girl, but Sheriff Henry Drew spent a day with Evans driving from town to town to check the story as it changed. Finally, after they had returned to the sheriff’s house, Sheriff Drew locked eyes with Evans and asked him if Georgie were alive or dead. After some seconds, Evans broke and admitted that she was dead. At midnight, he led the sheriff through a swamp to the body. On viewing the body, the sheriff demanded to know where certain body parts had gone to, and Evans led him to a spot where he had buried them under a rock.

Before his execution on February 18, 1874, Evans confessed to another murder and mutilation of a child which he had committed in 1850. He was suspected of committing several others, but denied his guilt in those. He requested that his body be sold to the Dartmouth College medical school for dissection, with the money to go to his son. And that is where we see him here.

Karen and Anethe Christensen, Smuttynose Island, Maine, 1873

Louis H. F. Wagner is the fellow on the left. The position of his hands suggests that he’s trying to hide shackles. Unfortunately, this “stereo” view is really two copies of the same photo, so it has no depth.

On March 5, 1873, Norwegian immigrants Maren Hontvet and her sister Karen and sister-in-law Anethe Christensen were asleep in a house on Smuttynose Island, one of the Isles of Shoals off the coasts of New Hampshire and Maine. Wagner had found out that Maren’s husband John was staying on the mainland that night, and he thought that John had saved up $600 for a new fishing boat. He also knew the house well, having lived there at one time. Breaking into the house, he blundered into Karen, who was sleeping in the kitchen. He beat her with a chair, but Maren managed to drag her into a bedroom and shut the door. Maren screamed to Anethe, in the next room, to run, and Anethe left by her window, but Wagner grabbed an axe and followed, and cut her down. When he came back into the house, Maren tried to get Karen to flee with her, but the badly-beaten Karen didn’t have the strength. Maren went out the window and ran, hearing Karen’s last cries behind her. Wagner searched the house and found $16, then made himself a meal, before rowing back to the mainland.

Wagner escaped from prison but was caught 3 days after in New Hampshire. He was hanged at Thomaston, Maine in 1875, more than 2 years after the crime. The murders were the subject of A Memorable Murder, which appears in many true-crime anthologies. The recent novel and movie, The Weight of Water also involve these murders.

Thomas and Simeon Sturtevant, Halifax, Massachusetts, 1874

William Sturtevant was in debt and thought his grand-uncles had money. On February 15, 1874, he grabbed a long wooden stake and headed to this, their house. Grand-Uncle Thomas was on his way to the barn to feed his cows when William bludgeoned him. He then went into the house and bludgeoned his bedridden Great Uncle Simeon. He rifled the house for money, and on his way out the door he killed the housekeeper, Mary Buckley.

The interest in his execution was so great that tickets had to be issued. Interestingly, Historic New England says that the photographer worked for the county. It would be interesting to know the county asked for stereo photos, or whether he took them to sell for his own business.

Russell and John Allison, Putnam County, Tennessee, 1875

Joseph and George Brassel were brothers who murdered Russell Allison in Putnam County, Tennessee, on November 29, 1875, in the course of an attempted robbery. When a posse came to arrest them, they killed John Allison in the fight. He was Russell Allison’s brother. While in jail, they tried to poison their guards with arsenic which had been smuggled in to them. Then they broke their shackle chains by twisting them back and forth for many hours. Later they tried crawling out under the floorboards, but there wasn’t enough space. Near the end, they converted to the Methodist church. They dictated an account of their lives, which they thought they could sell. It included a list of their other crimes, some quite vicious.

At their hanging, they were allowed to speak to the crowd, and warned them of the evils of alcohol. A long ballad was written about their crimes and execution.

Afterward

I know there are more true crime stereos out there, based on listings in library and historical-society catalogs. As far as I can tell, though, they don’t form a particularly common stereo genre.

For more stereo true crime, see Richard C. Ryder’s article Murder, Madness, Muybridge, and Gull in Stereo World; those issues are available online (Part 1, Part 2). Eadweard Muybridge was not only a proto-cinema pioneer, but also a great stereographer, and a murderer. Philip Glass wrote an opera about him, called The Photographer. Ryder also proposes a possible connection to Jack the Ripper.

Der Beitrag True Crime in Old Stereographs erschien zuerst auf the stereosite.

The story of 21 stereo glass negatives from the early stages of The Great War in Nevers, France.

The images in this post are anaglyphs and are best viewed by using 3D glasses.

The finding of a treasure

Last year, my attention was drawn to a collection of stereo negatives offered on eBay. It concerned 24 glass plate negatives in the format 8 x 18 cm (3.2 x 7.1 inches). The negatives show images of the mobilisation during the First World War in the city of Nevers in France.

The slides were offered individually, and I managed to get 21 out of 24. Unfortunately I was outbid on three slides, and that’s a shame because such a collection should stay together. But that’s part of the game. You win some and you loose some on eBay.

Two cardboard boxes with descriptions were also shown, but these were not part of the auction. Afterwards I’ve contacted the seller and asked if I could buy the boxes or possibly get a high resolution scan, because I suspected they contained valuable information about the negatives. The seller was kind enough to send the boxes for free because I bought most of the negatives.

The boxes

The two boxes are numbered with the numbers 30 and 31 in Roman numbers. According to the boxes, the total collection consisted of 34 negatives, of which 4 slides from box 31 are probably not related to the war, and were added to the box later.

24 glass plates were offered on eBay, so the collection was no longer complete when it was auctioned.

Of special note is that each negative is numbered, and the number relates to the descriptions on the box. The descriptions contain the subject, place and the exact date, which makes the collection historically significant. 

Stereoviews of the First World War were booming after the war, but those that were published in large volumes by publishers such as La Stéréoscopie Universelle or Brentano’s lack this kind of detailed information, or the information is simply not accurate.

About Nevers

The photos were taken on and around the railway station of Nevers. Nevers is located in the centre of France. It has a large railway station and was a logistically important hub for the French army. POW camps and several hospitals were built in and around Nevers during the conflict, which emphasises the importance of Nevers.

Some historic background

The negatives show images of the mobilisation of the French army. The First World War started on July 28, 1914. The direct cause was the assassination of archduke Frans Ferdinand of Austria-Hungary, but the real causes were lying deeper. The assassination triggered a chain reaction, causing all European powers to be at war with each other in a short time.

Germany had declared war on France on August 3, 1914. The photos of the collection were taken in August and October 1914. The first photo dates from August 9, so the war was less than a week old for the French. This makes it very special because images from the early stages of the conflict are rare. Most images date from 1915 to 1918.

In 1914 the war was welcomed by all participating countries, and the horrors of the trenches were still far away in those first weeks. Every country thought it would be victorious, and that all soldiers would be back home by Christmas.

This sentiment is clearly reflected in the photos. The atmosphere is patriotic and relaxed, with smiling soldiers.

What about the photographer?

The name of the photographer is unknown, but I guess it was a professional photographer. Stereo photography in France was dominated in the early 20th century by compact stereo cameras for the 45 x 107mm and 6 x 13cm formats. These formats were introduced by Jules Richard in 1893. He revived stereo photography in France, and his compact formats made photography accessible to amateurs.

Our photographer’s large 8 x 18cm negatives required a large, expensive camera and the skills to operate it, which is less obvious to an amateur. In addition, all negatives are accurately indexed and preserved, which indicates the work of a professional.

More negatives from the same photographer were offered by the seller on eBay. These did not contain images of the war, but were all numbered and indexed in the same way.

I suspect the photographer was from Nevers or the surrounding area, as the photos were taken on different days in August and October. A local photographer could be on site quickly.

My conclusion

I think the photographer was hired by the French army. Most of the photos are staged, which indicates that the photographer had permission to shoot, as photography was censored by the army during the war.

The First World War was the first major conflict in which photography played an important role. In May 1915 the French army founded its own photography section,  It was called La Section Photography de l’Armée. This section produced 120,000 photos during the conflict, including 20,000 stereo photos and a large collection of autochrome color images.

Before the creation of the SPA, the French Army simply hired professional photographers. This probably included our photographer, who had to capture the mobilisation for documentation, propaganda purposes, or to inform the public by newspapers. This also explains the accurate descriptions.

Why stereos?

Why did the photographer use a stereo camera? Stereos were primarily intended for entertainment and not necessarily for publication in albums or newspapers. My best guess is that this was just the only camera the photographer had, and the size of the negatives made it possible to use half stereos for printing without any problems. 

Special images

In September 1914, the German advance in France had come to a halt during the Battle of the Marne. From that moment, the Western Front turned into a horrible trench warfare that would last until November 1918. So no soldier would be at home for Christmas…

Der Beitrag The Nevers Collection erschien zuerst auf the stereosite.