resolution, useless & otherwise

[T3D Peter Abrahams <telscope@xxxxxxxxxx>]

>the resolution of the image... as it relates to stereo acuity which is many
>times finer than ordinary acuity.  But it seems like I keep coming
>up against the fact that the eye can see a lot of stereo in fuzzy 
>images.  Makes it seem like very little resolution is needed for 
>stereo, and what's needed for ordinary vision is only 1 minute of 
>arc, so why give more resolution than that?

I'm not sure that "what's needed for ordinary vision" is a meaningful
criteria, we have what biology & evolution (or what have you) have managed
to come up with.  Better vision would have undoubted survival advantages,
as well as enhancing our lives.   

To increase the resolution of the eye would require some fundamental
re-engineering, packing more receptors (shrinking the receptors?),
compromising the field of view, enlarging the skull, etc. Stereo acuity can
apparently be taken beyond ocular resolution without these extreme
measures, by the refinements of the eye & brain.
It would seem that stereo acuity would by its nature be better than the res
of one eye, since it has a 60mm base, in some ways comparable to the res of
an eye 60mm in diameter.  There are problems with the dual elements of the
binocular system, such as tracking, but when it works its pretty impressive.

As noted, one can see depth in defocused images.  If I take a Holmes card
with a lot of detail, and defocus it by viewing with a stereo viewer for
aerial photos, all of the fine detail gets fuzzy, but the larger forms
preserve most of their depth.  Much of the information in a focused image
is present if the image is defocused, for example it retains the color
(hue, saturation, & value).  Or, a very nearsighted person can catch a
basketball with no glasses.  However, one of the tests for stereo acuity
would probably show a dramatic fall off in acuity as the target is
defocused.  Or just try to catch a BB without your glasses, you might see
the glint of light but have a tough time anyway.

>For papers on stereo acuity vs resolution, see Gerald Westheimer.

Can you be more specific with that citation, is there a book?  I find about
40 listings in Howard & Rogers' Binocular Vision, but all for obtuse
sounding articles in professional journals.
_______________________________________
Peter Abrahams   telscope@xxxxxxxxxx
the history of the telescope, the microscope,
    and the prism binocular


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