P3D Re: Sharing Stereo

[fj834@xxxxxxxxxxxxxxxxxxxxx (Dr. George A. Themelis)]

Reply to message from asblair@xxxxxxxxxxx of Thu, 30 Jul

Quite possibly, the reason this lady could not see stereo, but was 
seeing double images instead is that her interocular (eye separation,
got this right Tony? :-)), is much smaller than the 64 mm standard
infinity separation of stereo mounted slides.

My wife cannot see VM in most viewers.  We have discussed this a couple
of times earlier in the list.  VM's infinity sepation is too high for 
kids, an unfortunate choice, but when the system was introduced, it was 
designed for adults, not kids.

If unusually small (or high, some times) interocular spacing is the problem
then the solution is viewers with larger lenses and introcular adjustment,
if possible.  Even though, in theory, interocular adjustment in a viewer
does not offer much, in practice, people with smaller or larger interocular
spacing, find it beneficial to adjust it.

I'd recommend creating a slide that tests ability to see stereo either
in the form of a hidden message in "random" dot/letter etc. images or
comparison of flat vs. 3d version of same image, and trying it with
different people.  I have a custom-made slide with random letters.  Some
of the letters are shifted, forming a message.  Those who can read the
hidden message definitely have sereopsis.  Those who cannot read it,
might or might not have stereopsis.  The time required to read it vary
from person to person.  I once thought to correlate this "response time"
with the person's degree of perception of stereo.... As we have discussed
in the list in the past, the degree of perception of stereo (manifested
also as degree of enjoyment when viewing stereo images) varies widely
among people.

-- George Themelis


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