Re: freeview/assisted view

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Bob Wier comments:
>Yes - we had a discussion on the effect awhile back (check the archives). 
>I don't know if we decided whether it was really an optical effect, 
>or psychological, or both... I see it quite strongly myself.

I find myself able to parallel view easiest so only recently with a lot of
practice has crossed viewing been comfortable for me. 

If you trace the visual paths from the eyes through each part of the image
to the convergence points seen while viewing, you find that there is a cone
of space expanding outwards from the eyes to the image and beyond. If you
are parallel viewing, the convergence is behind the image and is located in
the farther area of the cone, so appears magnified or larger. The deeper
into that space that you converge corresponding points of the image, the
greater the magnification.

In crossed viewing, the convergence is in front of the image so located in
the smaller more compressed area of this visual cone, so the stereo image is
correspondingly smaller. The more you have to cross your eyes, the smaller
the resulting apparent image.  I think that qualifies the effect as optical
in nature, though there are likely to be psychological effects to it as well.

The relative size change is most noticable in front of the image making the
shrinkage from crossed viewing very noticable. The magnification due to
parallel viewing is less noticable, but if you pay attention to these
comparisons as you try both viewing methods, you begin to be very aware of it.

Larry Berlin

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


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