: >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.