Re: pinhole photography/ calculating focal length

Bozhidar Dimitrov (
8 Jul 1997 07:47:37 GMT

Adam ( wrote:
: >"Geoffrey V. Brown" <> writes: > Well, I've got some extra film and want to mess around with some stuff
: >> this weekend.
: >> I'm thinking about trying some pinhole photos, but doing them with my
: >> canon T-90 with the lens removed and a plate in its place. I'm
: >> wondering how if anyone has any suggestions on how to calculate the
: >> focal length.

: >I do this often with a Pentax Spotmatic with a body cap with a pinhole in it.
: >It is about equal to a 45mm lens, and I would guess that it will be about
: >the same on a T-90.

It will depend on the camera register (distance between lens mount and
film). I thought about this some more last night, and I think that a
pinhole has no specific focal length. One definition of f is a distant
image is rendered the same size as through a pinhole f mm away from the
film. SO moving the pinhole back and forth (while adjusting the size of
the opening [for best results]) is like a zoom lens with an infinite range.

I think...
Boz Dimitrov