P3D Re: One-eyed Hollywood

[Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

Tony Alderson quotes:
>And Jim Norman wrote:
>>Don't be so sure that none could see in depth. I recall reading in a
>>medical journal some time agao (sorry I can't be more precise) of
>>instances in which one-eyed people achieve depth perception by subtle
>>side-to-side head movements, with the brain accommodating itself to retain
>>the sequential images and combine them into a perception of depth as
>>effectively as two-eyed people.

We two-eyed people :-) also do this unconsciously. For example on
a mountain range, people will shift their heads from left to right
(animals do this also) to get a better fix.

Tony writes:
>I think we need to distinguish between depth perception and stereopsis.
>Clearly none of these directors could see stereoscopically, even though
>they probably could construct a mental image of depth relationships from
>other cues.

I agree. There is an interesting note in the book, "Perception," It 
mentions, "Relative depth judgments based on motion parallax are almost
as accurate as those made using binocular disparity (Graham, 1965)."

>No, stereopsis is not a survival imperative. It clearly, however, gave our
>ancestors a marginal survival increase, which may have been very
>significant in the long run for our species.  Sure, one-eyed people can
>drive and live happy lives. Stereopsis just allows us to judge distances
>more quickly and accurately than would be possible without.  That probably
>makes a big difference for wild animals, and even for a few humans today.
>I'm sure you can cite one-eyed race car drivers, but I'd guess stereopsis
>makes the job easier and safer.

It could have been a survival factor, although not as a prey but rather
as predator. Continuing from the book...

 Why is the visual system designed in such a way as to provide two
 equally sensitive mechanisms (disparity and motion parallax) for
 seeing depth. Wouldn't it be safer to relocate the eyes on the
 side of the head, thus also producing a panoramic view of the world?
 The loss of disparity could be compensated by the equally effective
 use of motion parallax. 

 A possible answer to this puzzle they give is, frontal-eyed animals
 are usually predators. Movement of the hunter's head could forewarn
 the intended victim, thereby costing the hunter a meal.  

Wow, who ever thought 3-D could be so interesting! It should be noted,
that the sense of movement shouldn't be underestimated. Humans and 
most animal's peripheral vision is very sensitive to movement. Example,
if you look away from your monitor and look at it with your peripheral
vision, you'll might notice the flickering of the screen.

>Yours in depth (but without high-frequencies)

Maybe no high-frequencies but alot of high frequency ringing! ;-)

Gabriel



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