For regular parallel viewing, you only look at the left image with your left eye and the center image with your right eye. But for now, stare at the three pictures for a while. Allow your eyes to relax as if looking at a distant horizon. If you succeed, you will see four images instead of three. You have now succeeded in overlapping the three images. Now disregard the outer two images, and concentrate on the middle two. The center two images might be fuzzy for now, but with some concentration they can be clear and sharp in 3D. The left image in the center should be in 3D and the right image in the center should be 3D in reverse. If you see the right center image in good 3D, and the left center image in reversed 3D, you are viewing in cross-eyed, (see below).
To view cross-eyed stereo images, you need to look at the center image with your right eye, and at the right-hand image with your left eye (called convergent or cross-eye viewing). Below are a few tips on how to develop this skill using three images.
Gaze at the three images, but try to pay attention to the center and right images, keeping your eyes level (don't tilt your head left or right), now try crossing your eyes slowly, until you see four images. Paying close attention to the center two images, and ignoring the two outside flat images. When the center two images come together, (converge or fuse), you will see the center images as two different three-dimensional images, the right- center image will be in correct 3D, the left-center image will still be 3D, but in reverse. At first, the center two 3D images may be blurred. Keep trying to hold the stereo pair together while you focus. The longer you can hold it, the more time your eyes have to adjust their focus. Usually, even before you begin to get the hang of focusing, the two central images lock together, because your mind begins to interpret them as a two 3D objects.
Still having trouble? Here's another approach.
Cover up the left image with something. Now with your head level and about 2.5 feet from the screen, hold up a finger, with its tip about 6 inches in front of your face, and centered between the stereo pair on the screen. Focus on your finger tip, without focusing on the screen. Notice how many images you see there, (they will be blurred). If you see four images, move your finger slowly toward or away from you eyes, keeping focused on your finger tip, until the middle pair of images converge, which means you now see three images. With your finger still in place, partly covering the converged pair, change your focus to the screen. The image partly hidden by your finger should appear three-dimensional. Your finger should still appear single, but blurred. With some practice, you can remove your finger and still keep the screen images converged into a stereo image.
Stereoscopic viewing of these images requires concentration and may take some patience to master. If you are not successful after five minutes, try again after a few moments. Most people need a little time and practice, but once you can do it, you will remember it forever!
Try following all these directions to see cross-eyed at a distance. Again only looking at the center image and right images. Hold your right hand about a foot away from your eyes and make a circle with the thumb and index finger. Close your right eye and look with your left eye through the circle to the right image. Now, without moving your hand, close your left eye, open your right eye and look with it through the circle at the left image. Move your hand forward and back, until you can see the same part of the left and right images with your right and left eyes when you are looking with each by itself. Now, open both eyes at once and stare into the circle, so that you can see the two images on the screen in the background together. Get them to fuse in your mind into one, stereo image. This bit is a trick, and it might take some practice to make it happen. Once it happens, remove your hand and you should be able to keep your eyes crossed, with a little concentration, and keep the image in stereo.
© 2007 Jerry Oldaker. All rights reserved.