Re: PHOTO-3D digest 1377

[P3D Michael Kersenbrock <michaelk@xxxxxxxxxxx>]

> If you think of it as the *apertures* being shifted *outward* from
> the center of the lenses, and remember that the images are inverted, it
> is easy to see the shifting the left aperture to the left causes that
~
>... I prefer to think of the offset as a selective
>masking at the film plane.

Another way to look at the camera's construction (that enhances what Greg
wrote above) is to concider "what if" the film apertures were wider such
that they were twice as wide as they are now *and* centered exactly behind
each lens (disregard details about how the film is advanced).

In that situation we would have no "tilting" of angles or lenses or any of
that.  However (this is the crux of my posting) Realist 
camera apertures are *included* in this fully centered configuration! 
If I now cut the film that I take with this centered image camera, but
cut the film to half width and cut it slightly off-center, I end up
with the realist-camera images.

In other words, as Greg says, it's "selective masking" ahead of time.  One
could mount those full double-wide films with a realist mask and get the
same result as if a Realist camera took them -- but the mounting person would
have much more responsibility in getting it in the right place so it'll look
good (and perhaps consistent).

Mike K.


P.S. - I particularly liked "Three Dimentional Photography('53)" for this kind
       of "stuff" (basics easy to read w/o excessive details).  Of course there's 
       a lot of books I haven't read yet, so there may be many much better (and 
       maybe newer.  It also explains why one doesn't tilt the lenses in much more
       convincing detail than "not to produce keystoning".  Good advanced-newbie (me) 
       book.







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