P3D Slide Mounting Rotational Error Mis-Correction

[Michael Georgoff <Michael_Georgoff@xxxxxxxxxxxxxx>]

Fritz Waack done me wrong.  He does say to correct by rotation.  Hell,
beginners will believe anyone who writes a book, I suppose.

Thanks again for education.  George said (though not in this order) "Any
rotation (even a small one) will introduce a vertical displacement when the
displacement is projected in the vertical direction... Vertical
displacements cannot be fused by the eyes and cause eyestrain... The more
depth in a stereo pair, the more the horizontal displacements and the more
of a problem will be a specific rotation."

I almost get it.  In addition to introduction of vertical displacement, any
rotation introduces more depth.  This would add up to eyeball trouble in
fusing (fusion?).  Attempted correction of a stereo photography error
(non-level shooting) is actually error introduction at the reconstruction
end.

So, strictly speaking, it's a stereo no-no.  But the eye/brain accommodation
of this, and other errors or limits, is a personal accommodation thing.  My
brain might be able to make it "work" if I do some horizon straightening,
but it may fail for others.  

My personal lesson: Shoot as straight as you can, but mount straight (even
if horizon is off level), as attempts at correction introduce trouble.


Thanks.

Michael Georgoff
San Jose, CA

(Between the vignetting and the lack of a level, maybe I best put the
Realist 3.5 in the closet for a while and seek out a Kodak...)


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