Re: PHOTO-3D digest 1375

[P3D Neil Harrington <nharrington@xxxxxxxxxxxxx>]

LeRoy Barco writes:

>     The lenses aren't centered on the film apertures, but are shifted
>slightly inward. This lens shift creates one distance at which both lenses
>place the same visual field in the film apertures, which would not happen
>with parallel lens axes. 
[ . . . ]

>     Corrections, additional thinking, other viewpoints welcome...

One minor correction:  The lens axes ARE parallel, I believe.  You're
correct that they aren't centered on the film apertures, so that the viewing
angles of the lenses are slightly toed in, so to speak.  But if the lens
axes were not parallel there would be some keystoning.  Granted, the
keystoning would be very small with small angles of toe-in, but no purpose
would be served by doing this anyway.  As long as the frame apertures are
spaced slightly farther apart than the lenses, the camera will have slightly
converging angles of view (taking each view as a whole) while the lens axes
remain parallel. 


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