On Mon, 30 Jul 2001 15:11:14 -0400, you wrote:
>whereas the 28-105/3.5~4.5 is
>a "constant-aperture" lens (the maximum diameter of the diaphragm doesn't change
>(in principle), therefore the f-stop does change with focal length).
If this were *strictly* true, shouldn't we see a proportional change
in f-stop to the range of focal lengths? 28-105 is a range of about
3.5x and 3.5-4.5 is what, 2/3 stop?. My 75-300 has a zoom range of
4x, but is a f/4-5.6 lens, one full stop, or 2x. My 28-135 a bit
more than 4x, and is 3.5-5.6. My math is failing me now, but you get
the picture. So to speak.
Ken Durling
Website http://home.earthlink.net/~kdurling/
Alternate e-mail: [EMAIL PROTECTED]
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