Re: Stereo Window - Poll time!

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Fri, 20 Jun 1997
>From: P3D  Dr. George A. Themelis challenges:
>..................
>With a stereo viewer in mind (NO PROJECTION) I am asking:
>If the window is fixed, WHERE IS IT FIXED (at what distance
>from the observer) and HOW LARGE IS IT?
>
>I don't believe anyone can answer this question by looking at
>a slide in a viewer.
>

*****  I did precisely that while visiting Michael D'Abrosca the other day.
My chips were full frame and his mounts were 5 perf. We cut a couple larger
openings out of cardboard and did some exploring. I was able, by familiarity
with the process, to see exactly where the plane of coincidence was by
referencing the slide mount edges. Michael was surprised at this, but
quickly caught on to what to look for. He continued adjusting the chips we
were using and was able to clearly state that in a certain instance the
window was precisely behind one thing and in front of the other. I specified
where I wanted the window to be placed for this particular image and he
easily navigated the chips to that location, by referencing the results of
his work in a Themelized Red Button viewer.

Back to definitions. The window is defined as the plane of coincidence.
Wherever that is, you have a stereo window. It's natural place in projection
is the screen. On the computer with full screen displays using LCS glasses,
the natural window is the screen itself. In a hand held viewer it is at the
edge of your awareness where the mount itself forms the edges of what is
visible. Don't believe me, try playing with different sized mounts in a
viewer, and move the chips back and forth. That exercise is much easier to
do on the computer and is very instructional to learning what the window
really is.

The same is true for either a hand viewer or projector. It's a universal
stereoscopic phenomenon. Because of the function of a slide mount, that
device most often defines the window, by existing at the window. 

The window depth itself is not the only point of convergence while viewing a
stereo image. It is the *central most* depth within stereoscopic projection
and the natural resting place for your eyes. There is an apparentdoubling up
of images either side of the window.  The same identical image appears
larger when seen as behind the window, and proportionately smaller when in
front of the window due to projection issues. When you view a stereo image
you may converge your focus of attention to any point within the image all
the way from in front of the window out to infinity. That convergence is a
changing thing and becomes a significant part of the interpretation of the
image itself.

One can back off in the interpretation and see the wholness of the image
relative to the window, or focus in on small details and compare where they
exist spatially relative to other things nearby within the image.

 
Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/
http://3dzine.simplenet.com/


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