Pat wrote:
I purchased a used DA 16-50 from B&H, rated at 9+. I put the lens on
my K200D and immediately realize that the lens won't auto focus....
OTOH, when I place the lens on the *istDS, the lens will auto focus.
I'm guessing that the SDM component on the lens has failed. If that
is the case, will it not revert to the standard screw drive on a body
that has SDM ability?
_____
Yes, the SDM is faulty. If you get another copy of the lens, check
carefully for element misalighment, indicated by edge softness at the
right side. Oh, and some copies have it at the left side.
There have been many, many requests to Pentax to give us a firmware
option to use either SDM or shaft drive on DA* lenses that have both.
Pentax refuses to do this, and they will not acknowledge that there is a
problem. When SDM fails you may be able to focus manually. When the SDM
on my (second of three) DA* 50-135 failed in Rome last November, I
couldn't even turn the focus ring manually.
Until Pentax get these problems fixed, I won't buy any more SDM lenses.
Hoya has dramatically increased the price of lenses while refusing to
improve manufacturing quality.
Joe
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