Re: Those who cannot see or enjoy stereo

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Thu, 16 Oct 1997
>From: P3D  Gregory J. Wageman writes:
>
>Dr. T. observes:
>
>>One young fellow left in the middle of the
>>presentation.  Later he told me that he was getting a
>>headache.  ..............
>
>I'll throw my 2 cents into the stew (add metaphor; mix thoroughly).
>
>At NSA '97 I noticed that after long periods in the Stereo Theatre, my
>*neck muscles* were becoming sore.  I commented on this to Susan, and she
>said that hers were also.  My theory is that because one must hold one's
>head almost perfectly vertical for long periods, one doesn't do the usual,
>unconscious head tilts and movements which normally prevent muscle tension.
>I further theorize that in some people, this leads to headaches (or
>possibly, the muscle tension is mistaken for, or misreported as, a
>"headache").

*****  This is a very good observation. I did notice that there was a
negative reaction to tilting my head. I did not get a headache from it and
found myself occasionally tilting my head to explore the resulting ghosting
effect. Maybe that brief activity was enough to ward off the potential ache.
Another thing that is helpful during the odd moment when the projection
might be off during set-up or something is to simply close my eyes for a
brief moment. Once things are lined up again, it's easy to get back into the
images.

>
>One possible way to obtain evidence to support or discredit this theory
>would be to check with long-term users of LC shutter glasses, to see if
>they also report headaches.  Of course LCS users have a (hopefully) high-
>frequency flicker to contend with that slide viewers don't, but on the
>other hand the LCS glasses allow head movement without losing the stereo
>effect.

*****  I seldom if ever have a headache reaction to stereo viewing. I've
experienced fatigue from long term freeviewing when working on a project,
which could at times be described as a mild headache. I had no problems with
the NSA projection, other than noticing that tilt of the head was not
recommended. I spend relatively long times with LCS glasses without a
problem, though if someone were using a low frequency filcker rate, I can
see that could cause an occasional headache. When I'm stereo viewing with
LCS glasses, I notice that I tend to leave them on even during times when
I'm looking through Windows Explorer for more files and occasionally during
image editing. However, the flicker effect is exagerated when looking at the
standard screen, so after a while I do take the glasses off because it
*feels* easier and more comfortable without them. With a stereo image to
view, this feeling doesn't seem to exist.

>
>Use of circular rather than linear polarization should be better in this
>regard.  I wonder if any studies have been done...?
>

That would be a good reason to switch to circular polarization! Supposedly
it's not as strong or effective as linear polarization, but it seemed to
work well with the projected video at NSA. I haven't seen it used with slide
projection.

Larry Berlin

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


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