P3D Re: Re Stereo Base

[aifxtony@xxxxxxxxxxxxx (Tony Alderson)]

(This message seems to have been lost in the server problems, I'm resending it.)

Abram Klooswyk's illuminating posting (digest 2902) has got me pondering again.

This whole thread started with a request for a formula to determine an
appropriate baseline for a given scene. Some correspondents have puzzled
that there is no precise, agreed upon methodology after 150 some years of
stereography.

It seems to me an unreasonable request is being made of mathmatics. It
appears a formula is being sought to solve an aesthetic problem: what
baseline will make a stereo "look good." This is not really within the
realm of the depth-range equation.

Let's recall what the equation calculates: there are five variables: focal
length, interaxial, deviation, near distance and far distance. Given any
four, we can determine the fifth. But there isn't any formula for what lens
one "should" use for a stereograph; that's an aesthetic decision. The limit
on parallax is based on the conditions of viewing the stereo image, a
subject beyond the depth range equation. And knowing the near and far
limits of the scene, or what interaxial will "fill" the Standard Stereo
Viewing Space (I like this explanation Abram!) doesn't say what interaxial
will give a pleasing shape to the subject. Again, that's an aesthetic
decision.  (Except in engineering applications, where orthoscopy is
important; but I assume engineers can do math).

The most one can expect from the equation is the maximum interaxial that
will be projectable, for a given scene and a given theater.  And it is
helpful to derive some convenient rule of thumb for a first approximation
of stereo base. But math can't predict what interaxial will satisfy the
intent of the photographer, or taste of the audience . A formula for the
"perfect" interaxial seems about as likely as a formula for the "perfect"
color. There is beauty in mathmatics, but there is no equation for beauty.

That is why I bracket my slide bars: it allows an aesthetic decision to be
made aesthetically.

Tony Alderson
aifxtony@xxxxxxxxxxxxx



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