Orthostereoscopy

[P3D John Bercovitz <bercov@xxxxxxxxxxx>]

I think we need to make distinctions on the ortho bit.  Many writers 
consider violation of either of the main criteria an error.  I can't
quite do that myself because the two have such qualitatively different
effects and can legitimately be used creatively or for other purposes.
 
Hypo (stereobase < normal human eye spacing) is legitimately used in
macro stereo (as in taking a picture of a bug) to make the bug look
big and coincidentally not have too much on-film deviation.  How can
this be an error?
 
Hyper (stereobase > normal human eye spacing) is the only way to see
the Grand Canyon in true 3D.  How can this be an error?
 
Hypos and hypers reconstruct all three dimensions in proportion to each
other; if one dimension is reconstructed twice what it should be, so are 
all the others.
 
Stretch (viewing from too far away) can be used for effect.  As an
example, you might have a giraffe with his head and neck coming through
the window.  It might be fun to stretch his neck out for emphasis.
 
Squash (viewing from too close up) can also be used for effect.  You 
might want to take an airplane nose on and squash it to make it look 
funny.
 
Stretch and squash only affect the depth or third dimension; they have 
no effect on the other two dimensions.
 
Ortho is only useful when you want an exact reproduction.  It is also 
the easiest to digest - you'll have fewer viewer complaints, in general.
I'm personally not to fond of stretch or squash but have seen it used
to good effect.  I do like to make hypers and hypos to get an otherwise
unattainable view of the world.
 
John B


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