P3D Re: Realist mounting and the "stereo window"

[Paul Talbot <ptww@xxxxxxxxx>]

Dana asked:

> >Could someone define for me what the stereo window is, exactly?

and, as Greg W., mentioned, Dr. T supplied an excellent treatise
in reply, allowing the rest of just some nit-picking opportunities.  ;)

> "Exactly"?  No.  There is no mathematical definition.

Well, actually there is.  Charles Piper provides a mathematical
formula for the perceived location of the stereo window.  P3D's
resident formula wiz John B has elsewhere worked out a formula
as well.  And in the course of so doing, he determined that there
is a conceptual flaw in Piper's formula, causing a slightly different
mathemetical result for the window calculation.  But that's a topic
for off-list or Tech-3D.

> This stereo window is normally positioned at
> around 7 feet from the camera.

The "7 feet" figure is the most commonly mentioned one for the
built-in window.  But the built-in window is a function of *both*
the camera aperture offset and the mask aperture of the slide
mount used--as suggested by DrT's later reference to using a
different mask for closeup shots.  Piper's compilation includes
a chart of the "apparent window distance" for various combinations
of stereo cameras and different slide mounts.  For example, the
same slide mount that gives a 7 ft window distance with a Realist
gives a 9 ft window distance with a Kodak (or vice versa?).  I'm
trying to do this from memory, not having the chart right here,
so check Piper's chart if you need to know for sure.

Paul Talbot


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