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>sorry if this a dumb question, but I was curious:
>Is there a formula to compute the angle of view from the
>focal length and vice versa? Are there other relevant variables (e.g. film
>size)?
The basics:
- lens angle of view is generally given for the diagonal of the covered
rectangle (or circle).
- lens focal length is given for infinity focus.
- the diagonal of the film frame can be easily measured.
- given the above, using basic trigonometry, you can figure out either
the angle of view, or the focal length, if you know the other of them.
BTW, you will see as you try some, that with long lenses a doubling
of the FL very nearly halves the angle of view. As FL's get short, though,
this is no longer true (a 25mm lens does not have twice the angle of view
of a 50mm, for instance). And with most non-IF lenses, close focus reduces
the angle of view.
BTW, there are few dumb questions (but there are a few! ;-).
Hope This Helps