written for the stereosite by Pascal Martiné, Germany

Introduction

Many stereo photographers — especially those who are about to start with the medium — will at some point encounter problems when taking sequential stereo photos with their smartphone. This could be the wrong distance or rotation between the left and right image, the hassle of transferring the images to a computer for post-processing, automatic size reduction by collage apps, etc. There are common solutions and guides available for most of these single steps but this puzzle might get confusing or even frustrating for some. So better to switch to a stereo camera or build a stereo rig even if it’s expensive, heavy, and not always with me?

Personally, I really enjoy taking stereo photos of moving scenes with my Canon rig. But most opportunities are not worth taking the large bag with me and I also don’t have enough experience to make full use of all settings of the cameras. That’s why I actually hardly used my rig for almost two years. In fact, I’ve only used my smartphone and I definitely am convinced that this is a good choice — even for those who want to take stereoscopy more seriously.

Here are some examples of stereo photos taken at unexpected occasions. Luckily, I have my smartphone always with me.

Preliminary remarks

This tutorial is based on my personal workflow for creating side-by-side stereos and includes several apps for taking, aligning, combining, and post-processing stereophotos. From shot to post, all files stay entirely on the smartphone. Depending on the occasion I slightly modify my workflow by adding, replacing, or skipping particular steps. But on average the process really comes down to 3 minutes to get a finished side-by-side stereophoto. It needs a little practice of course, but in the end it’s neither more complicated nor more time consuming than finalizing the shots that I took with my rig. Using a ready-built stereo camera might be easier, but I did not try one of those because of the limitations of a fixed baseline.

That said, I’m using an iPhone 11 Pro and so my experiences are iOS-based. But all the apps I’m using are available for Android as well and should work quite similarly. The same goes for standard editing operations like cropping or duplicating images in your photos/gallery app. More recently, I started using Apple shortcuts to automate certain steps. But indeed, this doesn’t seem to be possible on Android. Therefore, in addition to providing the ready-to-use Apple shortcut, I will also explain the individual steps involved.

If anyone could provide detailed remarks on Android, I will be glad to update this tutorial later.

1: Taking the photos

As you might already know, the baseline (i.e. the horizontal shifting) between the left and right image is crucial for the depth and cannot be changed afterwards. Therefore, I recommend David Kuntz’s article about finding the right baseline for a stereo photo.

For now, what I  want to take away from it is to always take 3–5 photos in a sequence instead of only two. That way, you will have multiple stereo pairs with different baselines. No matter if you are experienced or a stereo beginner, you will always have at least one pair with the right depth. Furthermore, if you have two or more pairs with satisfying depth you may be able to sort out those with rivalries (i.e. movements or differences between the two shots that cause flickering in a stereo view). Finally, this method gives you also a kind of certainty while you take your photos: instead of thinking about the right baseline you can focus on a calm and relaxed parallel camera movement during your sequence and this will surely result in  better aligned photos (although possible, correcting the alignment is limited and causes cropping of your images).

In addition, I want to recommend always rotating your camera to shoot in landscape format. Keep in mind while choosing your point of view that the aspect ratio of your final stereo image may not be landscape, but sticking to landscape format ensures that later on you will be able to adjust the stereo window more easily. As this suggests, stereo photography includes cropping in most cases. You may be tempted to shoot in upright orientation, especially when you want to take quick snapshots in 3D, but you will lose more material than if you shoot in landscape format. The only exception I would note is an extremely narrow image format.

So, after a short while you will end up with hundreds of photos on your camera roll ready to make you despair. Thus, the next step takes the most patience in the whole process.

2: Finding the stereo pairs

Surely you have heard of the software Stereo Photo Maker and the corresponding mobile apps i3DStereoid (or 3DStereoid for Android) which we will use now. It is not possible to save files with the free version but I can promise you it’s worth every cent. Even though they’re sometimes a bit cumbersome to use, developer Masuji Suto deserves lots of recognition for developing multiple stereo apps independently in his spare time.

There are different tutorials and guides available for the app (iPhone-help, Android-help) where every function is explained in detail. Therefore, I will only explain the steps that are essential for this tutorial. I always use parallel view because that allows you to use a viewer or print cards. This tutorial works likewise for cross view, but if you want to use this or other different viewing methods, the later steps need to be modified. When first using the app, please set up for parallel or cross view in the bottom menu by tapping the eye-icon. As long as you want to follow this tutorial completely, you cannot use the frame feature. Tap on the ‘Main Menu’ button on the top left corner and choose ‘Open Stereo Image’ and navigate to your photos. Unfortunately, i3DStereoid won’t remember the last used folder so you will have to do this every time. There is a feature for easy flipping to the next image but it’s not suitable for our purpose.

Now you have to select two photos. You can do this by trial and error and improve with experience. But you can also free view the thumbnail images in different ways: you can fuse adjacent images, or every other image, or every two images, depending on the grid, though this will require a little more practice. Depending on the direction of your photo sequence the resulting stereo view will be either normal or inverted. But fortunately, either way lets you estimate the amount of depth of the stereopair and therefore helps you to choose the right one more quickly. Keep in mind that stereo photos look shallower at thumbnail size and will look deeper at full size. After you have determined the pair with the best depth you can now proceed as normal. Tapping on the ‘L‑R’ icon switches the two photos so that you can change between parallel and cross view.

3: Aligning the stereo pair

Without a bracket to guide the movement of your camera, it’s almost impossible to prevent vertical camera movement or rotation between the left and the right images. This makes it difficult or impossible to view the stereo photo, even with a viewer. Luckily, i3DStereoid has an amazing auto-alignment feature: just tap the white magician’s hat on the bottom menu and you are done.

Optional step: color adjustment

Sometimes the colors between the left and the right image are different due to the autofocus of your smartphone. More recently, i3DStereoid got a second magician’s hat (the colorful one). Tapping on it will adjust the colors of the two images to match better. If you tap once, the left image becomes the color reference; if you tap twice, the right image becomes the color reference; if you tap three times, all changes will be undone.

Optional step: vertical cropping

Although I’ve spent a few sentences on how to reduce the need for cropping, there are some cases that require additional cropping, e.g. if you simply want to remove something from the top or the bottom of the photo.

I have to add that I personally prefer my stereo photos to all have the same aspect ratio, be it  displaying them in a grid, or for printing them. Surely if you only want to display them on social media like Instagram different aspect ratios won’t matter that much. But if you want to keep a fixed aspect ratio, it is necessary that we crop only vertically in this step, or at least that we crop in a way that the result will still have a wide format.

The third icon on the bottom menu opens the ‘Adjust mode’. The stereopair is displayed interlaced and a blue cropping frame is displayed. You can adjust the frame easily with your hands.

Note about the stereo window

Let me take the opportunity to drop a few lines about the so-called stereo window here because that will be the next step we are about to prepare. The stereo window is created by the borders of your left and right images. In addition, their horizontal alignment will create a depth relation between the borders and the stereo photo. In other words, by adjusting the stereo window you determine if your subject is at the level of your screen, lies behind, or even pops out. Like the baseline, the stereo window is essential for a good stereophoto; however, unlike with the baseline, the position of the stereo window can always be corrected later. I highly recommend David Kuntz’s article on that topic to ensure you know how to achieve the desired effect and prevent a so-called window violation.

It is just as possible to adjust the stereo window in the ‘Adjust Mode’ of i3DStereoid. But since we have to switch to another app at some point anyway, I personally prefer adjusting the stereo window later. In particular, that is because I want to immediately see the stereo window while I’m working on it. But this is not possible with the interlaced display of i3DStereoid — even though this is useful for some purpose as well.

4: Intermediate file handling

To export the adjusted stereo image, open the main menu again and choose ‘Save Stereo Image’. Since we want to do further editing you should choose ‘Original resolution’ in the next step. Android users should export the stereo image twice — you will see why later. If you have more sequences that need processing I recommend repeating steps 2 and 3 now, so that you end up with a bunch of properly aligned and cropped stereophotos that are saved one after another on your camera roll. That way, you won’t need additional time to search through your pictures during the next steps.

a) iOS

Right now, the stereo pair is stored side-by-side in one image file. For further processing, we need to separate them. Luckily, Apple offers a kind of scripting tool called ‘Shortcuts’ that allows us to automate processes like this. I’ve written a suitable shortcut for our purpose that you can download if you open this link on your iPhone. You might need to adjust some settings first (more about that here, otherwise proceed as described for Android). After downloading the shortcut, you have two possibilities to run it: you can start it directly in the shortcut app, or on your Homescreen, or you can use the ShareSheet. In this case, open the photos app and select all the stereo images exported from i3DStereoid. Then tap on the share icon, scroll down and select ‘Divide Stereo Photos’. That’s it.

b) Android

The following fiddly step might not be necessary. Still, it could prevent exceeding resolution limits that would cause automatic size reduction. So, it’s best to check if skipping this step has any effect on your final stereo image. As stated above, you should have two copies of each of your stereo photos. Go through each of the files now and cut off the right part of one copy and the left part of the other. This should be possible with Android’s standard editing tools. You don’t need to carefully cut exactly in the middle — this is just to reduce the width.

Now you should have the left and right stereo images one after another, with the right depth, and perfectly aligned.

5: Adjusting the Stereo Window

Now we have to switch to another app that is extremely useful overall. Adobe Photoshop Express (iOS / Android) is also a mobile version of desktop software. It is free with some limitations but with enough functionality for our purpose. However, I recommend buying a yearly subscription because this opens a lot of useful functions for post-processing.

Start the app and navigate to the ‘Collage’ function. After our preparations it’s pretty easy to just select the stereo pairs and import them. The Layout section in the bottom menu lets you change the division between horizontal and vertical (mostly just titled G1 and G2). Tapping on the vertical division icon again switches the two photos so that you can change between parallel and cross view. The aspect ratio section lets you choose your desired format. I recommend 16x9 which results in almost square stereo views. The app also lets you directly choose formats suitable for purposes like Instagram posts or stories. (There are many more layout or zoom functions and plenty of online tutorials to dive into the app.) For now, that’s all we need to start with the stereo window adjustment: while you’re free-viewing the stereo photo, tap and hold one of the two images with your finger. Quickly slide your finger down out of your view. Now, while free viewing, move your finger horizontally and watch the stereo image moving forward and back in the stereo window. This technique enables you to determine exactly the best positioning for your photo.

There are basically two simple rules: moving the pictures towards each other will bring the stereo view closer, and moving the pictures away from each other will push them deeper into the window (when parallel viewing). By moving both in the same direction you can choose the image area. If a disturbing blue frame appears, just wait a few seconds and it will disappear. Sometimes you will accidentally zoom in, just double-tap to zoom out. No matters what happens, you have a comfortable undo function available.

If you are satisfied with the stereo window, tap on the share icon on the top of the screen. Then select ‘Save to camera roll’. If you navigate back to proceed with the next stereo pair, you can choose whether to save the collage or not.

Again, I would recommend repeating this step with each of your prepared stereopairs before the next step.

Parallel and cross grids

You may appreciate showing your images in parallel and cross-view right underneath each other in a square grid as is directly offered in i3DStereoid. I don’t recommend starting with a collage of four photos in Photoshop Express for that purpose. Instead, work as described using your preferred viewing method and export the collage once. Then switch the two images like described above and export again. That serves for the same stereo window in both versions. Afterwards, import both collages into a new collage without any additional borders. Sounds complicated? Well, that may be true. Maybe it’s better to adjust the stereo window in the ‘Adjust mode’ of i3DStereoid in this case.

6: Post processing

As you will know, Photoshop’s centerpiece is post-processing photos, and the same applies to Photoshop Express. If you choose ‘Edit’ instead of ‘Collage’ on the app’s start screen you can re-open the exported stereo photo, choose ‘Adjustments’ in the bottom menu, and apply different effects. Beside exposure, contrast, and other commonly-known settings, it’s especially useful to control highlights and white tones, and similarly shadows and black tones, independently. Try lightening up the shadows while darkening the black tones! Furthermore, I especially recommend ‘Clarity’ and ‘Dehaze’. Finally, artistic color adjustment is possible in the ‘HSL’ section where you can reduce or increase the saturation of specific colors. Most of these are only available in the paid version though.

If you’re done, you don’t need to export the picture manually. Just navigate back and confirm to save. A new copy will be created. Voilà — that’s your final stereo photo ready to post or send anywhere.

Alternatives

If you don’t want to subscribe to Photoshop Express or don’t feel comfortable using this app, it’s also possible to use the built-in iOS or Android image editing in a satisfying way. If that’s the case, you also might need to think carefully about how you want to adjust the stereo window. Like I mentioned above, this is possible in the ‘Adjustment mode’ of i3DStereoid. If you prefer the free-viewing adjustment, there are many collage apps available. But don’t forget to check whether they reduce the file size or insert unwanted watermarks.

7: Tidy up

Depending on your phone’s storage it might be necessary to delete some of the files that were generated during the process. If you repeated step 2 and 3 before starting off with Photoshop Express, and did likewise with step 5, you have your camera roll quite organized despite the large number of pictures. This makes it easy to choose which ones to delete and which ones to keep. I would only like to give you one piece of advice: you never know where you are going to present your pictures at some point. Whenever you change the medium in which you present stereophotos, it can be necessary to increase or decrease the baseline. So that’s another advantage of taking more than two images, and that’s why you should keep your original photos. You can store them somewhere on an external drive or card.

Conclusion

As I mentioned above the smartphone has become my number one device to take stereo photos. Of course, if I need to take simultaneous stereo photos, I take my stereo rig. But even then, I transfer the photos directly to my phone, and luckily, there is a cable for that. This is because of three more reasons that I don’t want to withhold from you: first, I have found a vivid and interested stereo community on Instagram — basically designed for use with a smartphone. Secondly, the smartphone is a really good viewing device, be it for free viewing, or be it inserted into a viewer like the LSC Owl. Even magnified phone screens don’t get as pixelated as computer monitors. Finally, not only do I have my smartphone always at hand to take stereo photos. I also have it readily available whenever I have to kill time. For those moments, what could be better than doing a few standard processing steps to get new stereo photos?

These photos required slightly more artistic post-processing but were still edited entirely on the smartphone.

Der Beitrag Stereo photography to go — from start to finish in 3 minutes erschien zuerst auf the stereosite.

There are two types of stereoscopic pairs, parallel view and cross view. Parallel displays the images with the right and left images aligned with the right and left eye. Cross view swaps right for left and requires that you cross your eyes to see the 3D effect. All traditional stereo cards are parallel view, and I enjoy being able to pick up a card and just free view it.

Theory

Normal view

When you first look at a stereo image pair, your left eye and your right eye each see the entire card, and your mind assembles that into one view of the entire card; a normal view. 

Double vision

When you allow your eyes to each focus on their ‘own’ side of the pair then each eye still sees the pair of images as they diverge, thus causing double vision. 

Merge 

This appears as three (or four) frames until you succeed in mentally merging the central, 3D image, and ignoring the outer frames.  

Unfortunately, this information is not especially helpful when learning to free view because the technique is not so much intellectual as it is physiological and psychological. But the following practice guide might be helpful. Though, don’t expect to be successful at the first time. You might be. Otherwise, take time…

Practice guide

I have to say that any written explanation of how to free view is difficult, because the technique varies a bit from person to person, and it is simply difficult to explain in words. Last but not least, free viewing has some advantages, but is not necessary if you have a viewer.

Sit in a comfortable chair that allows a stable position relative to the screen. Set up the stereo image about 5.5 to 6 inches wide (14 to 15 cm), level with the eyes, and at least arm’s length away to start (something like 24 to 28 inches; approx. 66cm). Some people may like to be farther away; the centers of the images should appear the same distance apart as your eyes.

Close (or block) your right eye; gaze at the left image with your left eye. Then switch: close (or block) your left eye; gaze at the right image with your right eye. Repeat, slowly several times. When each eye settles easily on its image then with one eye open, smoothly open the other eye without trying to focus — just gaze. Relax, and don’t attempt to concentrate, just allow the eyes to do what they do. You will see three images. Without changing the focus or direction of either eye, focus your mind on the central image. It will give the impression of depth to a greater or lesser degree. With practice you will be able to mentally block out the individual images and only see the 3D central image.

The first couple of times you may find your eyes changing back to normal focus, to see the pair as a pair. If you dont see what I’m describing after trying several times, try to relax and gaze over the top of the screen, maybe imagining you are looking across a room or out a window, just daydreaming. Without changing focus allow your gaze to move down to the stereo image pair, and you will see three images. Relax, let go of all expectations and the images will converge until you see the central image become 3D.

For Cross View, use the same sequence as in the first method, only with right eye to left image, and vice versa.  With a little practice you will experience a whole new dimension of photography!

These rather simple graphic images are chosen to allow easy parallel free viewing:

If you are able to free view these stereo pairs try the following photo.

Der Beitrag How To Free View Stereoscopic Pairs erschien zuerst auf the stereosite.

A 3D photograph usually consists of two images of the same subject taken from different viewpoints.  One of the most common questions amongst both experienced and new stereo photographers is how to determine the right distance (typically called baseline, stereo base, camera separation or interaxial distance) between the left and right camera positions that should be used when taking the photos.  The photograph illustrates what baseline is; again, it’s just the distance between the camera positions where the left and right images were made. 

Why Does Baseline Matter?

What difference does baseline make? Who even cares?  Well, to see why it’s important, let’s look at a series of 3D photographs of the same object made with progressively larger baselines.  In the sequence of cube photos, #1 starts with the smallest baseline, and the baseline is steadily increased through photo #9.

Depending upon how you’re viewing these images (which are made for parallel viewing), you’ll probably see almost no 3D in the first couple images.  Then, somewhere in the “medium baselines” set, maybe at image #5, the cube will look fairly “natural” and have a satisfying amount of depth.  In the last few images, the shape of the cube may start to look distorted, and it may even be hard for you to view it in 3D. 

Small Baselines

Medium Baselines

Large Baselines

Don’t worry about exactly which 3D of the cubes looks best to you – the takeaway is that too little baseline gives you almost no 3D effect, and too much baseline makes the image hard to view, or distorted looking. The right baseline gives you an image that has a satisfying amount of 3D, isn’t uncomfortable to view, and doesn’t distort the object (assuming you want to avoid that).  

What is the Right Baseline?

So, how do you know what the right baseline is for a specific photograph that you want to take?  The answer is, “It depends.”  And it depends on a lot of things.  Some of these are related to the subject material you’re photographing. These include:

• Subject size (especially subject depth)
• Subject distance (from the camera)

The other things that influence what baseline will work best have to do with the way you’re going to reproduce or view the image.  These include:

• Viewing screen or print size
• Viewing distance (from your eye to the display or print)
• Viewer type (particularly magnification if you’re not just freeviewing)

In particular, it’s important realize that the larger you’re going to reproduce your 3D image, the less overall depth it should have.  Similarly, the farther back you are from the display (or print), the less depth you should (typically) have.  So, an image meant to be viewed on a large screen TV should have less depth than one intended for viewing on a cellphone display.  

All this may seem like an awful lot of factors to consider.  And, exactly calculating or even estimating the right baseline value could be quite complicated, especially since you may not actually know all the information you need. But, there are a couple of ways to make it simpler.  

Practical Methods

If you’re taking sequential photos (that is, using a single camera to take the left and right images one after the other), then, you can just take several photos, gradually moving the camera in the same direction between each exposure. This is illustrated in the photo.  

After you’ve taken this series of photos, you view various combinations in 3D – for example, the leftmost photo with the one taken immediately to the right of it (#1 and #2), or the leftmost photo with the photo taken a couple of places farther to the right (#1 and #4).  Then, you just pick the pair of photos that look most satisfying to you.  

That’s exactly what was done with the cube photos.  It’s 10 photos of the same object, in which the camera was moved slightly to the right between each exposure.  Then, nine 3D pairs were made.  In each case, the leftmost original photo is on the left, and it’s then paired with ones on the right which were made at successively larger and larger baselines (#1 and #2, #1 and #3, #1 and #4…).  And again, you can just pick out the 3D pair that looks good to you. 

This may sound like a lot of work, but once you’ve had some experience you’ll get a feel for how much baseline works in a given situation.  Then, you’ll probably find yourself taking around five photos of a subject and getting one that works well when you start matching them up.

As I mentioned before, a specific 3D pair may look perfect on Instagram but might not be usable for a large screen projection. So, another benefit of shooting a sequence of images is that it enables you to create multiple 3D pairs having various amounts of depth for different purposes. And, even if you don’t want to do that right now, it’s worth saving all your images in case you want to go back later and produce another 3D with a different amount of depth. Perhaps your stereo photos will be part of a projected show sometime in the future.

If you’re shooting with a two-lensed 3D camera, like a Fuji W3, then your baseline is already set, and you can’t change it.  In this case, you control the depth in your photo by positioning yourself (and your camera) relative to the subject matter.  In other words, you might get closer to or farther from your main subject, or choose to keep elements that are very close or very far out of your composition.  

Specifically, when shooting with the Fuji W3 or W1, which have a stereo base of about 75 mm, arrange your photo so that the closest and farthest objects in it were at distances corresponding to the values in the table.  This will reliably produce images which are suitable for large screen viewing.  If you’re displaying your images on a small screen, you can stretch the depth range in your composition a little farther than this. 

Composition

It’s also important to realize that viewing comfort with a 3D photo depends on both total image depth, as well as the way that depth is distributed throughout the image.  The next drawing illustrates that.  It shows three series of circles.  In each case, the total depth between the orange and purple circles is the same.  However, for me personally, I find the top set, in which the orange and purple circles overlap, slightly unpleasant to view.  My gaze keeps shifting between the orange and purple circle, and the jump in depth between them is a bit annoying and difficult for me to take in.

In the set of circles in the center, the orange and purple circles still have the same relative depth relationship.  But, now there are three other circles in between them that act as stepping stones for my eyes, so that my gaze doesn’t have to shift suddenly from the foreground all the way to the background.  I don’t find it at all unpleasant to view this set of circles.

In the bottom set, the total depth between the orange and purple circles is again the same as before.  But, now they’re spaced farther apart horizontally.  I don’t have any trouble viewing this set either, probably because my eye has enough time to readjust as it moves over the large blank space in between them.

The lesson of this is that it’s not just the total depth that determines how comfortable a stereo image is to view.  The way that depth is distributed also plays a roll.

Let’s look at a real world example to see why this actually makes a difference.  This photo, taken at the Royal Palace in Munich, has a huge amount of depth.  But, I have no trouble or discomfort in viewing this image, because my eye is led gradually from the foreground to the background.  It’s just like the second set of circles in my first image, where I had a bunch of stepping stones to allow my eye to make the transition from closest to farthest object. 

The next photo of the flower also has a large amount of depth (too much!).  But, the real problem is that it’s distributed like in the very first set of circles, with the closest object (the flower) right in front of the farthest object (the wall).  Plus, there’s a distracting orange circle right next to the flower.  For me, this background element competes with the foreground, and my eye keeps shifting between them without knowing where to rest.  So, I find this less pleasant to view than the Munich Palace image. 

So, the lesson is, don’t just think about the total depth in your image when you’re composing a photo.  Also, consider how that depth is distributed and arranged.  And, try to avoid jarring transitions from very close to very distant objects.  

Get Creative

The discussion so far has mostly focused on viewing comfort.  In other words, creating images that are easy to view in 3D.  But, the depth of an image is also a creative tool.  Baseline can be employed in an artistic way, to purposefully make things perceptually appear larger or smaller than they actually are, or to distort or exaggerate depth.  For example, the next photo of the castle was taken with a fairly large baseline.  Most people looking at this image will see the subject matter as “miniaturized.”  Going in the opposite direction, it’s possible to take close-ups of flowers and insects at a very small baseline in order to make them appear gigantic.

Conclusion

Hopefully, you’re now aware that you need to control the overall amount of depth in your image to make it viewable.  And, that you have two primary tools at your control to accomplish this – the baseline you use when you take the photograph, and the amount of subject depth you have in your composition.  Plus, your viewing experience and comfort depend upon how you’re viewing the 3D image.  And, finally, that adjusting baseline is also a creative tool you can use to achieve a specific perceptual effect. 

It’s a lot to think about. But, don’t be paralyzed, trying to calculate or figure it all out before you take a 3D photo. The Stereo Sheriff isn’t going to arrest you if your results aren’t perfect.  Just become aware of what you’re doing.  In particular, the depth in your scene and the baseline you’re using.  Could you move slightly or point the camera differently to include or exclude something close to you in your composition (like an overhanging tree branch)?  These are the things you need to be aware of in 3D that aren’t an issue in flat photography.  

Just play around with it and take note of your results.  And, have fun!

Der Beitrag Getting the Right Depth in 3D Photography erschien zuerst auf the stereosite.

Stereo photography is a bit more demanding than traditional flat photography, because a poorly rendered 3D image can be difficult or unpleasant to view.  So, the stereo photographer has to take additional steps, not required with flat photos, to avoid the problems that lead to viewer discomfort.  The good news is that understanding a couple of relatively simple concepts will allow you to consistently produce 3D images that are easy to look at, and have good 3D impact.  And, once you’ve absorbed these ideas, it won’t take you any time at all to routinely perform the actions necessary to accomplish this.

What is the Stereo Window?

The series of three photos shown here illustrate a key 3D photography concept that affects viewing comfort, namely, the stereo window.  Imagine that your screen has a rectangular hole in it, and you’re viewing the 3D content in this image through it.  That is, you’re seeing the boy pointing his finger at you through a window in your screen.  The lattice of green lines in each image lies in the plane of your screen; in other words, your eyes see the green lines as being the same distance from you as your screen itself.

In the first 3D image pair (on top), the boy’s hand (which is the closest object in the composition to you), appears behind the green lines, or behind this window.  In the next stereo pair (the middle), his finger has been moved closer, so that his fingertip is right at the plane of the window; the exact same distance from you as the green lines.  In the last 3D image (bottom), his fingertip has now come through the window, and is closer to you than the green lattice of lines.

These three 3D images are all the same photo.  So, how did this transformation in terms of their depth relationship to the stereo window (or plane of the screen) between them occur?  The little red arrows between the photos indicate how it works.  If you compare the position of the boy’s eyes in each of the left side images with the leftmost green vertical line, you can see that the entire image has been moved slightly to the right in each successive pair.  The right side image doesn’t move at all.  This is possible because the original photo has lots of additional material off the left and right edges that is being cropped off here.  

This cropping, and how it relates to the window is shown again in the next two photos.  Here, you can see this image is cropped down quite a bit (in other words, there’s lots more in the original image that’s not being shown outside the frame of the crop).  But, by sliding the image left/right relative to cropping rectangle (or stereo window), the depth relationship of the subject matter with respect to the window is changed.  What is not changed, however, is the depth relationship of elements within the composition itself (such as the perceived depth distance from the tip of the boy’s finger to the background).  Those were set when the image was originally taken, and cannot be subsequently changed.  All, that’s happening here is an adjustment in the relationship of the image content with respect to the frame it’s contained in.  

Why worry about the Stereo Window?

The next series of photos is intended to demonstrate why you should care about the positioning of the stereo window relative to your photo.  In the first one, the flower petals at the edge of the frame are in front of the stereo window.  This causes a bit of visual confusion, especially at the left edge of the frame.  There’s also some “shimmering” at the frame edges, because there’s so much image material that shows up at the edge of one image that doesn’t appear at the corresponding edge of the other image.  

In the next photo, everything is far behind the stereo window.  This again causes a bit of “shimmering” on the left and right sides of the image because so much of what appears at the edges doesn’t match up between the left and right.  However, this version isn’t that unpleasant to view.  

The third image has everything in the image set just behind the window.  It’s comfortable to view, doesn’t have a lot of shimmering at the edges.

If the differences pointed out here aren’t obvious to you, don’t worry.  Your sensitivity to how the window is adjusted depends on a few factors.  First there are individual variations in how we each perceive stereo photos, and our tolerance for these adjustment factors.  Next, the size of your display, and your distance from it, are also important factors.  If you’re viewing this tutorial on a small phone screen, it’s quite possible that you either won’t see the differences between the last three photos, or won’t be bothered by them if you do.  But, as display size goes up, these differences become much more noticeable and disturbing.  When viewed on a large screen 3D TV, or if projected on a large screen, even much smaller differences than those illustrated here can produce a significant amount of viewing discomfort.  The takeaway from this is that if you’re only showing your images on Instagram, you don’t need to worry about all this nearly as much as if you’re projecting them for a crowd. 

How Do I Control the Stereo Window?

So, if you now understand the need to set the position of your subject matter with respect to the stereo window, the next question is how to accomplish that.  That turns out to be the easy part.

Two of the applications that can be used to readily perform this adjustment are the Windows-based program StereoPhotoMaker, and the corresponding iPhone/Android app, 3DStereoid (both produced by Masuji Suto).  No matter which program you use, the very first step you should take, before performing this window adjustment, is to “auto-align” your image.  This gets rid of any vertical, rotational, perspective or other misalignments that can make a 3D image uncomfortable to view. 

With auto-alignment complete, set the window in StereoPhoto Maker by going to the “Adjust” menu, and then selecting “Easy Adjustment.”  This brings up a large dialog box with lots of options, along with your image displayed in anaglyph (red/cyan) format.  To adjust the window, just use the slider at the top of the window (indicated in red).  This allows you to move the two images horizontally relative to each other.  As explained previously, this will change the relationship of your subject matter to the stereo window.  

Another option in StereoPhoto Maker is to stay in the main program window, and then just use the left and right arrow keys to make this adjustment.  Each press of the arrow key shifts the image a small amount, so it’s easier to use the Easy Adjustment menu if a large shift is needed in order to get the right window setting.  This adjustment can be performed with your image displayed in virtually any format; anaglyph, parallel pair, cross-eye pair, and so on.  So, you should probably choose a display method which you are actually able to view in 3D.  

In the 3DStereoid app, this same functionality is available by selecting “Edit” from the main menu.  Then, the left and right arrow buttons (indicated in yellow in the graphic) will shift the images relative to one another.

How do you know when you’ve got it right?  Any part of your photo that doesn’t have a red or blue fringe (that is, the red and blue images are perfectly overlapped there) when viewed in anaglyph is right at the stereo window.  This situation is illustrated in the next graphic, which shows that the right side of the rightmost flower in the image has no color fringing, and will therefore be exactly at the stereo window in terms of depth.  The petal next to that does show a fringe, and won’t be at the window.  It can be helpful to view your image through anaglyph (red/cyan) glasses during this process to visualize the relationship of subject material to stereo window, or alternately, in another format that you can actually view in stereo. Often, a final step of cropping your 3D image may be helpful after setting the window.  This can be helpful to eliminate parts of your photo that don’t match up well or are visually distracting after windowing has been performed.

Conclusion

Hopefully, this tutorial has shown you the need for stereo window adjustment and it’s benefits, and given you a simple, easy to use method for performing that adjustment. The key takeaways to remember are:

Der Beitrag Stereo Window basics erschien zuerst auf the stereosite.