I had a pinhole photography (noncredit) class at the University of
Minnesota last spring. There was a lot of variation on the pinhole
cameras that people used. A couple of people bought high-end pinhole
cameras that used Polaroid 4x5 film. One person built a couple of wooden
box cameras that used the same 4x5 film and film holders. Another person
used a body cap with a hole in it to modify a 35mm camera into a pinhole
camera. I took a 120 box camera (bought at a garage sale) and replaced
its lens (a small single element glass lens) with a pinhole.
I have seen older plans that require 126 film cartridges, but because of
limited availability, I didn't try that route. The 120 film I use is
T-Max 100 and 400, mainly because it behaves better when subject to
reciprocity failure. (It requires only longer exposures, not changes in
developing, which is required for Plus-X and Tri-X, for example.) Some of
my exposures were as long as 10 or 20 minutes, depending on lighting
conditions.
David S. Cargo