I performed my own little test of distortion with the 35-80/2.8 at
35mm. I tried but didn't successfully get the film plane precisely
parallel to the wall, so I don't think these tests are definitive by
any means, but I think it is still possible to get an idea of the
problem.
There are three frames: 1) 35-80/2.8 at 35mm, 2) 35/2.8 shift
(unshifted) for comparison, and 3) 35-80/2.8 at 40mm (to see at
what stage the problem goes away)
I made shots at 40mm, 45mm, and 50mm to see at what point there is
no longer any distortion. I didn't include the 45mm and 50mm shots
because I felt the distortion was gone at 40mm. There almost looks
like a waveform distortion in the 40mm shot, though focus is not as
good and the lines of this wall are not ideally straight for tests
of this nature. (Live and learn.) I probably should have focused
directly on the wall, but I didn't (the main subject is the red
pump). The difference in DOF between 35mm and 40mm at f4 may be a
factor of some sort.
At least from these shots I will be operating henceforth under the
assumption that distortion is basically gone by 40mm. The 35/2.8
shift shot gives one a reference on the quirks of the wall itself,
and in relation to that the 40mm shot looks quite good to me.
Anyway, see for yourselves here:
http://soli.inav.net/~jdub/35distortion.html
Joel W.
There is also, apparently, a little darkening in the corners for both
the 35mm shots. Were these wide open?
--
Winsor Crosby
Long Beach, California, USA
mailto:wincros@xxxxxxxxxxx
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