Viewing stereo pairs. There are two types - cross-eyed and wide-eyed:

Cross-eyed: This seems easier for most people to manage to view.

First, don’t be anxious about the “crossing your eyes” phrase - all that means is that you’re focusing at about the level you’d need to see your finger six inches in front of your face. You do that all the time.

Sit 2-3 feet back from the screen. Look at the line where the two panels join. Cross your eyes slightly, and a third panel will appear between the two. Continue crossing your eyes until the images in the left panel completely merge with their counterparts in the right panel. At that point the effort of crossing your eyes will disappear and the 3-D image will snap effortless into focus - it’s very odd.

If you have trouble with this, hold your finger up about six inches in front of your nose and focus on it. That’s the level of eye-crossedness you need. Now slowly pull your finger down out of the way without breaking your focus and the third panel should be there, close to what you want.

Notice that I’m using the word “focus” rather loosely. Your finger should not be in sharp relief, just bring the two fingers together into one - by “focus” here I really mean “positioning your eyeballs”. Once that’s done right, your eyes will really focus.

Wide-eyed: These appear to be harder for most people to manage, and even one beer destroys the ability for me to do it.

To view the image, sit back about 3 feet and gaze toward the screen, but don’t focus directly on it. Relax. Let your eyes defocus as you would when daydreaming. Start out by pretending to focus about a foot *behind* the screen. A third image will appear between the two sides of the picture. Let the image on the left and the image on the right come together. Play around with your focus until the middle image comes into sharpness, and you’ll get a 3-D view.

Don’t try to cross your eyes; if it’s uncomfortable, you’re not doing it right. This is a zen thing.

What’s happening in the cross-eyed approach is that your right eye is viewing the left panel, and the left eye is viewing the right panel. They accomplish this by focusing on a point between you and the image. This is in contrast to wide-eyed approach in which your left eye views the left panel while the right eye views the right panel; this is accomplished by focusing at a point far behind the image. (Normally of course your eyes are viewing BOTH panels, focusing directly on the image.)

The difference between the wide-eyed and cross-eyed approach is simply the order of the panels; switch the left and right panels to turn one into the other.

One expensive way is to use two slightly offset cameras at once, but that's not necessary. Taking the two slightly offset pictures with a single camera is easy. Find a distant target in your camera’s view of a likely subject, center it in the viewfinder in a way you can remember, and take the pic. Now without moving away from or toward the subject, step a foot to the right. Again center that distant target in the viewfinder and take the pic. The first pic will be your right panel and the second will be your left panel if you’re doing crossed-eyes. If you’re doing wide-open, you reverse the panels.

Ideally you should be centering your viewfinder at infinity. With landscape shots this is usually easy. With macro shots it may be harder - you might have to intuitively guess at what is infinity behind the magnified image you're trying to take. It is NOT appropriate to center on the same spot in the image you're trying to take - you won't get a 3-D stereo pair that way. Rather, shift the camera slightly to the left or right, and recenter the viewfinder on a spot slightly to the right or left (respectively) of the initial shot.