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08-25-2010, 06:09 PM   #1
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K10D (and other bodies) AF adjust values

Background:
I'd been having issues with shots not being in focus, which I thought was due to my main lens (DA21) having been knocked around quite a bit, and confirmed this morning that the combination of the lens and my K10D was back-focusing quite a bit. This afternoon, I was lucky to be able to pick up a DA35 at B&H, and after seeing the same issue on this pristine lens, figured it must be my body. I got home, went through the AF adjustments detailed in this thread, and ended up with much better results from both lenses... after making a +330um adjustment!

A third of a millimeter seems like a tremendously large distance for a mechanism with ordinarily such small tolerances.

I was wondering what adjustment values others have seen successful in the past?

08-26-2010, 02:11 AM   #2
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-110 on my K-m.
08-26-2010, 02:18 AM   #3
axl
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On my previous K10D I had to do +240 to get FA43 to focus correctly. Problem with K10/20 is that the mirror seems to develop play over the time or after some knocks and this AF problem is then getting progressively worse (since the AF sensors are at the rear of the mirror). This was the case with my previous K10D. When I got FA43 all it needed was +110 to get things right. 7 months later I had to be setting it to +240! Keep an eye on this....
-------
here is my thread about it:
https://www.pentaxforums.com/forums/pentax-dslr-discussion/97312-k10d-deterio...-possible.html
08-26-2010, 06:29 PM   #4
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I think you're definitely right about the mirror. I noticed shooting today that my adjustments had been a bit off, but more worryingly, when the image is in sharpest focus in the viewfinder (when manual focusing), its out of focus when it hits the sensor, which must mean the mirror is out of whack enough to not line up with the sensor properly.

I'm sure I'll be able to compensate for this with AF microadjustment, and get it so that the lens auto-focuses properly, the problem will be that when it does focus properly, I'll think it hasn't!

08-27-2010, 04:52 AM   #5
axl
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QuoteOriginally posted by dantekgeek Quote
I think you're definitely right about the mirror. I noticed shooting today that my adjustments had been a bit off, but more worryingly, when the image is in sharpest focus in the viewfinder (when manual focusing), its out of focus when it hits the sensor, which must mean the mirror is out of whack enough to not line up with the sensor properly.

I'm sure I'll be able to compensate for this with AF microadjustment, and get it so that the lens auto-focuses properly, the problem will be that when it does focus properly, I'll think it hasn't!
There is a remedy for this. Use shim(s) to adjust the position that it is aligned with the mirror. First, set your AF adjustment so you are 100% sure it's spot on (ideally with something quite a bit longer than 21ltd) and then use the shim(s) to adjust the screen so it shows correct focus when the lens is in focus according your AF. Bit tedious but it works. I used to do it with my previous K10. Ultimately though you will have to have your body serviced or buy new one because this issue tends to deteriorate rapidly once it occurs (at least on my camera it did).

Regards
Peter
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