P3D Re: Pulfrich

[Dave Combs <dcombs@xxxxxxxxxxxxxxxx>]

Dave Spacey wrote:

>Are you sure one eye is a whole frame behind the other?  Only if the
>filter is dark enough to add exactly 1/30th of a second to the time to
>process.
>
>The brain does a lot of "tweening" in the process of perception, without
>which movies wouldn't work at all.  You could easily be just a half of a
>frame behind in the right eye.
>
>Just a thought.
>
You are correct in that one eye is not exactly a whole frame behind the 
other. In fact I set up an experiment with a video camera and a turntable 
on which I had placed a paper disc with spokes printed at intervals which 
represent 1/30 sec of rotation. I had expected to demonstrate that at a 
certain degree of opaqueness or darkness of the filter that the delay 
would be 1/30 of a sec. It wasn't. The delay is apparently much shorter 
than that. In any case I concluded that the delay obviously did not have 
to be a whole frame, only long enough for the brain to perceive the 
image. So there is only a split second during which the eyes are viewing 
different frames--enough to give the Pulfrich effect of 3-D.

I wish that someone would devise an experiment to actually measure and 
chart the actual delays using various levels of neutral filter 
transmissivity. This would be very interesting and make a great thesis 
for some technical paper. So far I have not been able to find anyone on 
the planet who has done such an experiment. (Maybe the sunglasses 
manufacturers lobby has buried such a study somewhere since they would 
not want the general public to know that sunglasses actually affect a 
person's visual reaction time by a measurable amount. :-) )

Dave Combs
Combs Music International
421 Cedar Trail
Winston-Salem, NC 27104 USA
E-mail: dave@xxxxxxxxxxxxxx
Internet Home Page: www.combsmusic.com
800-932-6627 (USA & Canada)
336-760-0037
336-760-3855 (fax)


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