Re: Why 3D

[P3D Morris M. Keesan <keesan@xxxxxxxxxxxxx>]

Julius Martin wrote:
>I've often thought about setting up a wall with two eye holes
>and a well lit stereoscopic view on the other side of the wall to demon-
>strate the idea. If there is nothing in the view that would move,
>I don't think anyone would be able to discern whether what was seen
>was real or a photograph.  After all, everything is fused in the brain
>into depth, and if the eyes see what they would have seen at the moment
>of the stereoview, how can the brain know the difference?

The answer is that the brain knows the difference because of where the focus
of the eye is (Jim Crowell or others will correct me if I'm wrong, but I
think this is called "accomodation", as well).  The only depth cue we get in
stereo photos that's not in flat photos is parallax ("convergence" in the
eye), but when viewing a stereo photo, our eyes are focussed at a single
depth. I can easily see depth, in the real world, with one eye, by holding my
finger out at arm's length, and alternately looking at my finger and at
things in the background.  When I look at the background, my finger is out of
focus, and vice versa.  When viewing a stereo photograph, all items are
typically always in focus, whether or not they're what the eye is paying
attention to.

out at 
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Morris M. Keesan -- keesan@xxxxxxxxxxxxx


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