pinhole photography/ calculating focal length

Geoffrey V. Brown (
Mon, 07 Jul 1997 08:37:44 -0400

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.