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.
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