photographing small; projecting big?

[T3D Richard Young <young@xxxxxxx>]

Say we have an object 20 feet away that is about 15' wide. We do a 3-D
shoot using 65 mm separation between camera positions (for left and right
images), using a 35 mm lens, and the object just about fills our 35 mm film
in width. We then project onto a 12' wide screen that is 12' away, using 35
mm projector lenses for the Left and Right images. Great -- people see the
original object in 3-D at the original distance, as we intended.

Now however, we have 1/3 scale model of an object (that is, it is now only
5' wide) . The question is -- at what distance, with what lens, and at what
camera separation should the object be photographed, such that if we use
the identical projection situation as above -- 12' screen that is 12' away,
with 35 mm projector lenses -- will the object appear to be a full-scale
model of the object (that is, it should be seen as 15' wide, with no
distortion, seen at the same 20 foot distance as the full scale object)?
There may be no exact solution -- but can anyone recommend at least an
approximate one that would produce good results? Are there any good books
that would shed some light on this subject?

The solution would be easier in 2-D (look at all the sea-battle scenes
filmed in miniature for the film industry), but I don't believe the answer
is so obvious for 3-D, if you want things to look right.

- Dick Young



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End of TECH-3D Digest 152
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