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About Stereoscopy

There are many ways to produce stereoscopic images. The nature method, of course, where the brain creates a plastic image out of the two slightly different pictures that each of our eyes perceives.

Artificial three-dimensional images were hard to fabricate before the invention of photography. Painters could not easily produce two pictures from different perspectives, where the deviation was as small as that which occurs between the right and left eye.

The urge to see the world captured with maintained plasticity seems powerful, since stereoscopic photography was an early branch of this new medium. Cameras with two lenses were constructed, but often did photographers use one camera only. This could be done when the subject was static. The camera was mounted on a sort of sledge, on which it could slide a few inches between exposures. Many animals - certain owls for instance - perceive depth and/or distance this way, by moving their heads from side to side.

Maybe the image of the topless lady in the Art Bin's 3D section could be such a sequential stereogram. Here the model seems to have moved during the procedure. Her facial expression is not exactly the same in the left and the right picture. When viewed, especially if the differences between the individual pictures are bigger, images of this kind convey a strange, floating perception of depth, time - and even motion - simultaneously.

With the reversal film new possibilities emerged. When the images are projected on a screen, they can be merged and separated again if the spectator wears glasses. Either anaglyph specs with one red and one green filter for the left and right eye respectively (a technique that also works in print) - or - with polaroid filters, which is a better method, since the projected images need not be reduced to red/green only - they can be shown in full color. With this technique the images are separated not by color but by the polarization. One image is projected with light waves of horisontal polarization and the other with waves of vertical polarization.

Other techniques for 3D were developed too. Holography was invented in the late 40's by Dennis Gabor. He did not get full recognition for this until 1971, however. This was when he received the Nobel prize.

Today the so called SIRDs have become popular. Here, one single image with a complex pattern, might be interpreted by the eyes as two separate images, a sort of interference retraced or at work backwards.

(See also The Patch Stereogram Project)

© Copyright Karl-Erik Tallmo 1995
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