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08-28-2010, 12:30 AM   #1
emr
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DFA 100mm f/2.8 WR problem

I have the mentioned WR macro and while it mostly works just fine, every now and then I get quick-shift focus related problems. Usually I can easily rotate the quick-shift as it is supposed to, but sometimes it gets "stuck" so that there's a friction and I can feel something turning, probably the AF motor in the body. Haven't of course done that a lot due to the fear of breaking the AF motor. This has not happened with other lenses on the same K20D body. Also, switching to MF and back to AF does not help. When the lens is off the camera body, I can see that switching to MF completely retracts the AF screw. Then, having focused normally with the camera body (AF button or shutter release), the problem goes usually away.

Has this happened to anybody else and do you think it could be anything else than a malfunctioning lens? The lens is still under warranty and I guess I'll send it to the service site. The reason for not having done that already is that there's only one official service in the whole country (of Finland) and my previous experience with them wasn't positive. (I sent my malfunctioning K200D there twice and after whatever they did to it, it was still the same, but that's another story)

08-28-2010, 01:40 PM   #2
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Happens to all my non-SDM DA lenses with QS too. I believe it has to do with the way the QS "clutch" was design and best left the AF finished its turn b4 trying to MF. But when it jammed, don't try to MF, just AF a little will free it up.
08-28-2010, 01:54 PM   #3
emr
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Thanks! Then I probably won't send it to the useless service site. I only wonder about this thread having 173 readers and only you report the same problem. Hasn't anybody else experienced this?
08-28-2010, 02:13 PM   #4
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Only had my 100 WR for a week but have not experienced this problem as yet.

08-28-2010, 03:32 PM   #5
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I've actually taken to manual focusing mine most of the time because in most situations I find myself in, it's easier and quicker. The quick shift on this particular lens has never really impressed me as the AF wants to take over anyway (if I'm half pressing the shutter release).

Usually, the camera gods can tell which lens I have mounted, they already know what I want to do with it, as soon as I bring the camera up to focus, they kick up a good strong wind. It can be dead calm all day. As soon as I mount a macro lens of any sort, hurricane force winds.

08-28-2010, 04:04 PM   #6
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QuoteOriginally posted by JeffJS Quote
...
Usually, the camera gods can tell which lens I have mounted, they already know what I want to do with it, as soon as I bring the camera up to focus, they kick up a good strong wind. It can be dead calm all day. As soon as I mount a macro lens of any sort, hurricane force winds.

Oh thank god. I thought I was the only one the camera gods hated. its good to see this happening to others.
08-28-2010, 04:27 PM   #7
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All my QS lenses are like that too, even the DA 40 limited. It happens WAY more often on the MZ rather than the K-digital series bodies though.
08-28-2010, 05:05 PM   #8
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I think the reason is that the QS was designed during the DSLR era and Pentax DSLRs AF were designed to kick back a little so that the QS clutch will be disengaged. If the camera didn't kick back slightly at the end of the AF cycle, the QS might jam. This is my observation anyway.

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