|How to Take Stereo Photos|
Getting Started with 3D Photography
by Terry Wilson
Why take just one picture when you can easily take a stereo pair? With a digital camera, there's no film to waste, and you can preview the results if you have a flip-out screen.
A stereo pair consists of two pictures, one for the left eye and one for the right eye. Even though the two pictures may look very similar, they are not identical. When viewing a stereo image, the left eye sees the left picture and the right eye the right picture; then the brain fuses the two images and you perceive depth.
You don't need anything fancy. You can record the two pictures using one camera. However, one limitation of using a single camera is that you are restricted to subjects that don't move between the two shots. This includes leaves fluttering on trees, running water, moving clouds, and of course people and animals. If you wait too long between shots, even shadows move amazingly fast. But learning to use this technique allows you to take spontaneous stereo images. Most of my stereo images are taken with a single digital camera.
Keep it level. Keep the camera horizontal, and facing forward (do not toe in), or aligning the pictures will be a problem later. When you frame your subject, make a note of features near the top and bottom borders and use that for alignment. For a normal scene within say, voice range, shift the camera by about 2.5 inches (the approximate spacing of the eyes) between the two pictures. One technique for doing this is called the cha-cha. This name derives from the idea of shifting your weight onto one leg, then the other, to give you about the right spacing. If you are lucky enough to have a convenient flat ledge or rail, you can set your camera on it to maintain a levelness and also gauge your distance more accurately.
Lens spacing. You will need different spacings for subjects very far away or very close up. A distant object, such as a mountain, will work with several feet between pictures (just keep any foreground objects out of the picture). From an airplane, it is easy: just aim out the window and take pictures a few seconds apart. Likewise, a macro shot of a flower's stamen will work with only a half-inch or so separation. The idea is to think in terms of the angle, not the lens spacing. Try to imagine the relationship between your two eyes, and the subject. The angle formed when viewing everyday objects ranges from a few degrees (something across the yard) to maybe 10 degrees (reading a book).
Viewing the pictures. Now that you have two pictures, you need to learn to view them as a pair without using any special glasses or viewers. This is the best way to quickly know if you've made a successful shot or not. I you remember the Magic Eye books popular about 15 years ago, this is the same eye technique used for what's called "parallel viewing" (as opposed to "crosseyed viewing"). Basically, you put the two images side by side, with the left image on the left, right on the right. Now look at them and relax your eyes, so they actually drift apart. As they do this, guide them so the two images drift into three, until the image in the middle pops into alignment as your stereo image. You are now compositing the left and right images on top of each other, and letting your brain focus on this image alone. Once you get it there, you can easily lock it into place. If this is difficult, try reversing the pictures (right on the left, left on the right) and crossing your eyes until the third image locks into place in the middle. Some people find this easier. If your digital camera has a flip out screen, preview your pictures in a grid so your pairs are side by side. Then freeview them to see if your depth is enough or not. You won't discern any detail, but amazingly enough, you can tell if there's depth or not.
Subject matter. Sometimes a scene is all wrong for flat photography, but ideal for stereo. A subject with a busy background can kill a photograph by distracting from, and even obscuring, the main subject. But if the busy background complements the subject in some way, the depth difference can work in your favor. Sometimes a subject is wonderful to behold in real life, but a photo disappoints. With stereo, you can capture the interplay of the layering that made it interesting in the first place.
And then some. This should be enough to get you started, but there are many other ways to take stereo images, such as mounting your camera on a slide bar, syncing two cameras to fire together, having two people press the shutters on two cameras simultaneously (often used with landscapes where the cameras are several yards apart), and of course using a stereo camera like a Realist. Viewing stereo images comes in different flavors also. Slides in viewers, slides projected on a screen, stereocards in a viewer, anaglyph prints with red/cyan glasses, Viewmaster reels, and a few other formats.