Re: Dominating eye -> stereoblindness ???

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Sun, 12 Jan 1997 20:36:54 +0000
>From: P3D  Dr. George A. Themelis  observes:
>
>I just made an interesting discovery... 
>
>You know how by freeviewing you can find the differences.....
>....  I am talking about the "Find the differences" cartoons in
>newspapers and puzzle magazines. 
>
>I copied the two pictures.......snip.....
>I plan to include this slide in my "scientific 3d" talk (not 
>very scientific but the idea does have some practical uses).

*****   Great idea!!!

>
>I put the slide in a viewer and showed it my wife explaining that this
>is what I see when I freeview the cartoons.  "Sorry, I don't understand... 
>what do you mean?"  what her reaction...  "What two pictures? I only see 
>ONE picture!"
>
>Hmmm... Houston, we have a problem... ;)

****  Sounds like teaching people to see stereograms!

>......snip ....... but with both eyes open she could only
>see the long beak which was the LEFT picture and had NO clue that there
>was a second different picture involved.
>
>Clearly, with both eyes open, her left eye is dominating.

*****  Quite typical I think.

>..............snip.................
>I have heard some talk about "dominating eyes".  Can that explain the
>very different people's reactions when exposed to stereo images?  Are
>people who have one "strong" (dominating) eye less impressed by stereo 
>than those who have "equal strengths" in both eyes?  Is this thing
>measurable?  Any studies, statistics on the subject?


****  I'm sure it'a a part of the situation. It's also a situation that is
not fixed. You can train your eyes and mind to be more aware of these
differences. We probably all have dominating eyes. Further, normal eyesight
seems to compensate for missing information by selecting the most available
information as dominant, such as *seeing around corners*. When the effect is
very strong by habit or other condition, it reduces the stereo effect by
very significant amounts or even obliterates it.

I can't offer statistics but I've encountered this many times with lots of
people and have played with it in my own experience. Specifically, once you
become aware of this controllable element, you can learn to shift your
mental awareness from one eye to the other while both eyes are open. Eye
dominance can be overcome somewhat with training of awareness.

Since I work on stereo images while viewing them, I frequently need to
determine which side, left or right, is the cursor really on? Which side of
the pair needs fixing? I sometimes alternate eyes but also have learned to
block out one or the other at will while both eyes are open and in viewing mode.

One test that I find fun is to have a repeating pattern in which the colors
are different. Which color do you perceive when viewing it in stereo? I did
that with some Chrismas paper this year. The stripes were red and green,
which were nearly impossible to merge as some combination of both. With
practice, I could be aware of either color, which is by extension awareness
of one eye or the other's viewpoint. It helps if there is a strong border of
other feature in the images which otherwise are large spaces with different
coloring. The features, best in black or other high contrast color, lock in
the stereo viewing aspects and allow you to easily work on the color without
losing fusion of the images.

I believe this is mostly a mental-image-processing kind of thing and is
established early in one's life. There is no one who can direct you to be
more aware of how this develops. Some of it could be in the complexities of
the genetic coding itself, which provides tendencies to one thing or
another. If awareness of stereopsis is weak, only repeated exposure and
exploration of the phenomenon can improve the ability, but it can be improved.

Larry Berlin

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


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