P3D spherical field parallax distortions

[John Toeppen <toeppen@xxxxxxxx>]

Abram wrote: "the depth squeeze deformation by the long lenses (2d
deformation) affects only one of the three dimensions: depth, so it
cannot be corrected by the base deformation only.......by enlarging the
base even more, so that photographic convergence is increased too, will
do the trick."
I may not be getting the point here.  The orthoscopic effect -
flattening of distance with long lenses - eliminates the depth cue of
the diminution of size of an object at a distance - a total lack of the
"fisheye" effect. The telephone poles along the desert road appear to
all be the same size independent of distance.
These effects are related to field of view and the "mapping" of a 
spherical field onto the image plane of the film.  This kind of
"distortion" is corrected if the image appears to have the same angular
size for the viewer as it did for the photographer.  In stereo close-ups
with the Realist this seems to be one of the problems - the difference
in distortions from the two perspective may be as bad as the exaggerated
divergence/convergence.
What this means to me is that we should use wide or normal lenses when
shooting our hypers of landscapes.  Those of us that do electronic image
cropping know how to create the telephoto effect.  
One of my current approaches has included using 35 mm fl lenses on my
Nikkormats on 7.5" centers and producing interlaced images that are
2,400 x 4,000 pixels.  Now, any 1024 x 768 windowing of that image is
nominally "stereo correct" because I have effectively "zoomed in" and
reduced my effective baseline.
I have also used 2 1/2" base line and zoomed in with lenses to flatten
the field for macros.  Abram is quite correct about this working well. 
I think that is the FOV thing.  I certainly think that is worth shooting
a bit to see these effects for ourselves.  Some of my favorite shots
come from testing the principles and defining the space in the envelope.

John Toeppen
large interlaced and anaglyph images that overfill your screen 1,800 by
1,900 pixels at:
http://members.home.net/toeppen/index3.htm