"F. Craig Callahan" wrote:
> is it the case that the angle of view of a 90mm lens in 35 mm format will necessarily
> be roughly the same as the angle of view of that lens's 4x5 equivalent (equivalent in
> terms of magnification and depth compression/exaggeration)?
Ah . . . a quick consultation of Michael Langford's "Basic Photography," 6th ed. (Focal
Press, 1997--highly recommended!) reveals the following:
"[A] lens of short focal length used with a small-format camera gives the same *angle
of
view* as a lens of longer focal length used in a bigger camera. You are just scaling
everything up and down" (p. 37).
And then there's a handy chart (p. 82) that lists different angles of view and their
focal
lengths for different film formats; for a "normal" AOV of 46�, the focal lengths are
50 mm
(135), 93 mm (6x6) 105 mm (6x7), 180 mm (4x5), and 360 mm (8x10). Of course--doh!--the
necessary focal length doubles when doubling film size (i.e., 4x5 vs. 8x10). A
corollary
to this is the remark that "angle of view is inversely proportional to focal length.
For
example, a 100 mm lens gives half the angle and twice the image magnification of a 50
mm
lens, assuming distant subjects" (p. 78)--and also assuming the same film format.
So my "common sense" speculation was incorrect, as "common sense" conclusions often are
(being based on unexamined assumptions).
:-)
Craig
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