Re: Stretch and squash

[P3D Dr. George A. Themelis <fj834@xxxxxxxxxxxxxxxxxxxxx>]

Those who wonder about the manifestations/application of "squash" in stereo
images, consider these two cases:

1. Portraits taken with 135 mm SLR lenses and viewed in a regular slide
viewer.  The result is that the distance from the nose to the ears appears
compressed and that gives the impression that the nose is smaller and the
ears larger, which is fine if you have a large nose and small ears, but a
problem the other way around!

2.  Sometime ago I talked about a stereo pictures of crosses taken in
Arlington national cemetery.  This was taken with a Realist and was
subsequently "stretched" in projection.  A good project would be to try and
record this scene using longer focal length lenses to compress the depth
and make the pattern of the crosses look more impressive.  Other pictures
with patters would also work better with "squash".

The "stretch/squash" phenomenon in not unique to 3d.  It also occurs in 2d
photography and most of us are familiar with the "compressing" effect of
longer focal length lenses and "expanding" effect of wide angle lenses. 
The principle is the same.

George Themelis


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