RE: Random Stereograms

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Wed, 26 Feb 1997 6:12:58 -0600
>From: P3D  Chuck Field writes:
>.......................
>  I have never been able to pull an image out of a stereogram.  It also took 
>me a year to learn how to free-view stereo pairs.  My eyes stay out of focus 
>for at least two minutes, after doing so.  I have to wonder if I'm trying to 
>free-view crosseyed.  The pictures in Stereo World do not look pseudo, to me.
>  So I've always assumed that I was free-viewing correctly.  But then, maybe 
>I just can't tell the difference.
>    Could I be able to free-view true stereo pairs properly, but NOT be able 
>to view a stereogram?  It doesn't make any sense to me.
>   Any thoughts on this?  
>Chuck Field
>ECF004@xxxxxxxxxxxxx

The process is the same but the stereogram pattern may be more difficult
because it is a random pattern so presents more of a challenge for
interpretation than a stereo pair, for some people. The biggest cause of
discomfort or stress during attempts to freeview is that as a newcomer to
that process a person tends to overuse the eyes by trying all ranges of
motion in an effort to force the issue. After you finally get it worked out,
it takes very little real effort so becomes something you can do for
relatively long periods of time. I regularly spend many hours each day
freeviewing as I work on images.

The very best advice is to relax and give it time. If you can freeview
stereo pairs but not stereograms, try placing a stereo pair image on top of
a stereogram. View the stereo pair first and in a relaxed manner allow
awareness of the stereogram patterns to grow by itself. It would be best to
make the size of the stereo pair you are using small enough to match the
obvious average repetition of the patterns in the stereogram. That would
make the stereogram pattern coexistent with the stereo pair and facilitate
being able to see both with relative ease. Once you *get it* it gets easier.

I strongly recommend that you teach yourself both parallel viewing and
crossed viewing. By using both methods you strengthen opposing sets of eye
muscles reducing the amount of difficulty involved in freeviewing. This
helps prevent over use of some muscles compared to others which can make
returning to normal vision difficult at times. The other big advantage is
that with crossed viewing you can enjoy much higher resolution images than
is physically possible with parallel viewing.

There is additional hope for those of you who have traditionally had
difficulty with stereograms. LCS glasses!!! With this technology you can
easily set up the views to allow viewing of a stereogram without teaching
your eyes new tricks. Within the realm of viewing with LCS glasses you can
still use and/or learn the techniques of freeviewing so it's possible to see
the stereogram as a flat pattern, displaced from the screen depth, or as a
3D image at the screen depth in the same manner as you would scan your eyes
througout the full depth of an ordinary 3D photo. If a person views a
stereogram through LCS glasses it would become easier to obtain the same
view without the LCS glasses because of the knowledge of what it contains.

Larry Berlin

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


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