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03-22-2009, 02:50 PM   #1
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AF adjustment problem. Different corners, different focus results.

I have tested my lens on AF adjustment chart. The lens is Pentax 31 mm. F/1,8.
After number of tests I am confused. In the left side of a chart I see perfect results with exact focus on -00-, while in the right side it performs about 3 mm. front focus. Adjustment in my K20D does not help as one side of the lens shows perfect results. The lens is still in the warranty time period. Should I send it back? How to react on this?


03-22-2009, 04:37 PM   #2
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
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Either jump up and down and scream like a baby, or just get out and take pictures.
Odds are, there is a problem with your testing procedure, not with the lens, but either way, you don't want to open up a lens for something that insignificant.
03-22-2009, 06:49 PM   #3
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Location: Melbourne, Australia
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I would not bother the fine tuning of the autofocus on k20d. You would have to fine tune everytime a different lens is used.

Back focusing does happen from time to time. Just test it in the field instead of doing these tests that are not indicative of true applications of this lens.
03-22-2009, 06:50 PM   #4
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3mm doesn't sound like much. but if one side is sharper than the other and might be worth sending it back for decentering issues.
do you have any samples?


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