Re: Dangers of freeviewing (repost)

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

Dr. George T. writes:
>In chapter 3, "Fundamentals of Photo Inerpretation", the author 
>Ellis L. Rabben writes the following about freeviewing:
> 
>   "Naked-eye stereoscopic vision is an interesting and 
>   often convenient stunt.  If adopted as a habitual 
>   practice, however, it can cause accommodation and 
>   convergence to assume a new and anomalous 
>   relationship.  The interpreter may then see double, 
>   or his vision may blur, at odd times, because the 
>   stabilizing relationship between accommodation and 
>   convergence has been disrupted."
> 
>I wonder if there is any scientific truth to this statement.  If 
>not, as I suspect, then how come it found its way in what appears 
>a reliable & scientific reference? 
>-----
>George Themelis, freeviewing with no side-effects (yet!)

The question of scientific *truth* is a very subjective one despite the fact
that it deals with supposedly scientific details that are somehow
*provable*. Such things are especially subjective when it comes to
describing non-exact processes which is true of most biological functions.
In this case I suspect the author is at least partially right. Whether he
speaks from conjecture or from experience isn't clear.

I do a large amount of free-viewing and have noticed tendencies for such
problems to come up once in a while. Sometimes there is difficulty getting
normal convergence to happen again after considerable parallel viewing.
Since I can parallel view easier than crossed viewing, I figured that too
much viewing in the *easy* way was the problem. My solution was to persist
in learning crossed viewing. It seems that toning muscles in both directions
keeps the facility balanced and generates fewer problems. This is consistent
with other muscle related exercises where proper toning is beneficial. Too
much exercise in too limited a way can lead to problems especially in vision
where the balance between delicate muscles is critical.

The author claims the relationship between accommodation and convergence
becomes *disrupted*. I think that is an exageration. The eyes are capable of
being trained with these viewing techniques to a degree that just about any
stereogram or stereo pair is instantly viewable. I no longer need narrow and
specific conditions to allow free-viewing to take place. I can freely adjust
my eyes, ignoring garbled results or extraneous side imagery until the
correct relationship for a given image is obtained. In multi-dimensional
images I can freely explore most of the levels at which stereo information
is available.  I believe anyone is capable of learning such methods and
developing corresponding muscle tone so that normal sight isn't disrupted.
All of the actual positions of muscle and eye used in most free-viewing are
within normal movement ranges, just a slightly different combination of
them. Practice builds familiarity as well as muscle tone and precise
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conscious control of what is normally a subconscious adjustment.

>John Merritt asks:
>The question for all of you free-viewers out there is:
>have you ever experienced any trouble with focus or
>fixation (blurred or doubled vision) after you began
>the sporadic practice of free viewing?  
>
>Any such effects right after free viewing?  Any at "odd times" ??
>

My answers: none of these effects until long after doing it extensively, not
sporadically. Occasional blurred or doubled imagery after viewing parallel.
Much less occasional instances at *odd-times*. Whether the odd times thing
even counts is questionalbe because I freeview so easily and do it quite
often. Once my eyes are *re-set* to normal there seems to be no problem. Now
that I regularly do crossed eye viewing as well as parallel, problems seem
much less frequent. I think balanced muscle tone is important.

Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/


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