<Quote>
I was shocked when I noticed the terrible edge
sharpness at f3.5. Then calmed down because it's at
(too) short distance and I guess I did a really bad
job
focussing. What do you think? Is it my fault? The
other photographs seem ok.
</Quote>
Jochen,
I'm on the digest, so you've probably received several
more helpful responses by now. Here is my take on
your results. First, the 21 f/3.5 is not a flat field
lens, meaning that it will have a curved plane of
focus. You are shooting a flat map, so the edges and
corners are significantly farther away then the
center, and therefor out of the narrow DOF. The
higher your magnification, the shallower your depth of
field. Also, as someone already pointed out, the lens
is designed and optimized for use somewhere near
infinity, which means that your overall lens
performance is somewhat less at close distances. I
think that you must've been very close to the map with
that 21mm lens. In your photos, I think that the
curved DOF was the primary cause of your poor corner
and edge sharpness. That is not fault of the lens, it
just wasn't designed for that, macros are.
All that said, the true test of a lens are the photos
that you make with it, and I like both of the corn
shots and the vines with that one little spot of red.
Nice!
Marten
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