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05-29-2010, 11:24 PM   #1
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DA* 200mm - Unusual SDM Behavior?

After a lot of soul searching, I finally sold off a bunch of gear to free up some funds for a lens that I've wanted since my film days: a prime 200mm F2.8.

Picked up this gem of a lens from Adorama and took possession the other day on my way into the U.S. on a vacation to Portland (pics will be posted later).

Spent the day shooting pretty much only with the 200mm today and while it is superbly sharp and seems to behave 99% of the time, I have noticed some odd behavior and wanted to see what other DA* prime owners might think.

Basically, the lens will generally lock on focus pretty much immediately without a lot of back and forth adjustment. It's quiet, so can be hard to tell when the focus starts and finishes; meanwhile, the image just magically sharpens in the viewfinder and you get the focus lock confirmation.

However, every once in a while, the lens gets a mind of its own and despite being able to focus properly, it (or the camera?) loses the ability to focus and will focus back and forth trying to find the proper focus point before stopping and the focus lock light starts blinking. Changing subjects doesn't seem to snap the lens out of the state and only a quick flip to the on/off switch and/or AF/MF switch seems to recover the ability to focus.

I'm still doing some testing to see what conditions bring about the focus issue but in the meantime, I'm wondering if anyone (aside from dgaies) has noticed a similar issue? It's not an issue of whether the SDM motors work (I can hear the motors quietly whirring away and there is no hesitation for the motors to spin up and try to focus) so I'm wondering if it's something else?

Thanks in advance.

05-30-2010, 03:00 AM   #2
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QuoteOriginally posted by legacyb4 Quote
However, every once in a while, the lens gets a mind of its own and despite being able to focus properly, it (or the camera?) loses the ability to focus and will focus back and forth trying to find the proper focus point before stopping and the focus lock light starts blinking. Changing subjects doesn't seem to snap the lens out of the state and only a quick flip to the on/off switch and/or AF/MF switch seems to recover the ability to focus.
Can you say anything else about the state of the camera? Was it AF-C, AF-A, AF-S? Were you shooting in (really) low light or was it at daylight? I don't own any DA* so I can't help further, but this looks like low-light hunting or something with AF-C more than a problem of the lens itself.
05-30-2010, 07:41 AM   #3
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It happened in both outdoor and indoor lighting conditions under AF-S mode; it seems once the lens has trouble locking in focus, it's unable to get focus lock back until I reset the lens (turning power off/on).

Will do some more testing today and see what happens.
05-30-2010, 08:38 AM   #4
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Did you notice any correlation between the distance to the object and difficulty getting a focus confirmation?

05-30-2010, 11:04 AM   #5
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If there is a lot of stuff in the foreground or background, the camera may have been trying to lock focus on something other than your intended target. I have had that happen often with my standard screwdrive telephotos. Usually, it's the background and the way I tried to frame the photo that causes it to go nuts. If you're photographing a barn in decent light that takes up much of the frame, then there may be a problem.
05-30-2010, 11:06 AM   #6
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QuoteOriginally posted by legacyb4 Quote
It happened in both outdoor and indoor lighting conditions under AF-S mode; it seems once the lens has trouble locking in focus, it's unable to get focus lock back until I reset the lens (turning power off/on).

Will do some more testing today and see what happens.
Now that I reread your post, I think it's probably a different than the issue than the one I described that happen to my previous copy of the 17-70. When it was having issues locking, I could get it to lock by just releasing the half-press of the shutter (or AF button) and starting over; I never had to turn the body on and off. Do you happen to have a second body (w/SDM support) to try with the DA*200?
06-12-2010, 02:49 PM   #7
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I did try it out on dugrant153's K7 and it exhibited the same behaviour so I contacted Adorama who has arranged for an exchange.

Here's to hoping I don't get another lemon!
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