Homepage | Color Stereo Directory About Stereograms
by Gene Levine
There is a lot of information on the Internet concerning all aspects of autostereogram history, science, and creation. There are even programs and/or programming code available to make make your own SIS or SIRDS. Since it is my wish to promote autostereograms as an art, rather than a science, I'll only try and give a quick overview of what we're dealing with. I make no real claim to accuracy.
A stereogram is a flat two dimensional image viewed in such a fashion as to produce a three-dimensional effect. Traditionally done with opto-mechanical devices: when such an effect is accomplished with the eyes alone it is an autostereogram.
From birth, we learn to view the world using our normal stereo-vision. With this, each eye focuses on an object, seeing the same object on the same plane, but that small distance between each eye feeds the brain enough different information to give our minds a sense of depth. This phenomena is called stereopsis.
Stereopsis takes place within the brain, and that is key to the stereogram 3D effect. But unlike normal convergent vision, with stereograms we either diverge or cross our eyes to feed the brain subtle differences in a pair of objects.
There are several kinds of autostereograms, but only two ways to view them for the 3D effect. (Figures 2, & 3)
PARALLEL VISION: Each eye locks on the image separately but parallel, as opposed to converging as with normal vision. This is the most commonly used way for viewing autostereograms.
CROSS-EYED VISION: Each eye views the image separately, but right eye views left side, and left eye views right.
Unlike normal viewing, the stereo offset is innate to the stereo image, not the environment. The brain does not care, and the subtle differences within an image's pattern create the 3D effect.
There is much confusion between Parallel and cross-eyed viewing. The effect is essentially the opposite. Eventually, your eyes will tell you which works with what. To the best of my knowledge, all hidden-image stereograms require parallel viewing. All stereograms on this site are made for parallel viewing. Cross-eyed viewing is frequently used for stereo-pairs. Cross-eyed viewing is more likely to cause eyestrain.
An interesting esthetic with a stereogram is no matter how profound the effect of depth is, all is in focus at one time. After all, it is really a two-dimensional representation. This is what often gives a stereogram its ethereal, meditative appeal.
For more info: Wikipedia - Stereogram
http://en.wikipedia.org/wiki/Stereogram
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