At 20:12 2/4/01, Frank van Lindert asked:
Jim, why the cable release?
Frank.
I'd be willing to guess that exposure will be measured in tens of seconds
with an aperture in the high double-digits to low triple-digits.
It will depend on how he designs the pinhole (distance from the film plane)
and speed of film used. Technically, a pinhole has no focal length, but
the distance of the hole to the film plane (on axis) is often described as
if it were one. There is an optimal diameter for a given hole-to-film
distance . . . with several different philosophies about how "optimal" is
defined. A hole too small suffers from diffraction limits. A flat film
plane will have cos^4 falloff whereas a curved film plane will reduce the
effect.
Extension tubes would be ideal for increasing the distance from the film
plane. A separate pinhole with optimal diameter would have to be made for
each combination of tubes though. Sorta like changing lenses again!
A body cap pinhole would give new meaning to the term "pancake lens." I
have a couple old generics for the OM system that are about half the
thickness of the Oly ones.
A good source for learning more about pinholes is here (the URL should
_not_ be a big surprise):
http://www.pinhole.com/
-- John
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