> What the heck is inverse quadratic diminution? Maybe I shouldn't ask!
> I believe you are seeing vignetting. I it seems more pronounced on
> large format cameras with a short focal length.
For a flat film plane, the light from a pinhole falls off as the forth
power of the cosine of the angle from the center of the image. One factor
of cosine squared is due to the increasing distance from pinhole to film
and the other factor of cosine squared is due to the fact that when viewed
from an angle, the round pinhole looks like an increasingly smaller
ellipse. That's why the corners get dark in wide angle pictures. On the
other hand, an oatmeal box or other cylinderical camera corrects for these
factors.
Received on Fri Dec 14 10:22:16 2001
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