The Ives Kromskop

written by Paul Wing, USA. First published in Stereo World 1988 (15/1), used with kind permission of the National Stereoscopic Association.

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.

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.

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.