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08-01-2010, 10:37 AM   #1
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AKum8's Avatar

Join Date: Jul 2010
Location: Milan
Posts: 89
Front back focus calibration - K20D

Hello guys, recently I bought a DA* 16-50 and yesterday I found out that some pictures shot at 50mm f/2.8 were out of focus.

Today I made some test with a couple of objects and it results that my K20D + 16-50 is affected by front focus.

I tried to calibrate it, and here is the result:
(focus on the middle battery, crop 100%)



My best result is when the calibration is set to +10. I would like to increase this value in order to improve the autofocus tuning. Is it possible in some way?


08-01-2010, 11:04 AM   #2
philbaum's Avatar

Join Date: Oct 2007
Location: Port Townsend, Washington State, USA
Posts: 3,659
small detail, but if the battery on the right is closer to the camera, then the lens/camera combo is backfocusing. Also +10 adjustment moves the focus towards front focus.

To answer your question, the answer is yes and no Yes, you could technically get a +20 adjustment. This would be done by dialing in a +10 for "all" lenses and a +10 for just this one lens.

But before you do such an adjustment, you'd probably want to check some of your other lenses to see where they and the camera are. Make a list and put down for each lens how much back Focus or front focus they have. If they are all back focusing to some degree, then using an all adjustment would help them all.

You could temporarily put in +10 for all and then adjust for this specific lens to see how bad it is. Then make a report this adjustment problem when, or if you send the lens in for an adjustment at a repair center. My brother recently sent his sigma zoom lens, 70 to 300mm, into a "precision" lens repair place on the east coast, recommended by Pentax, and they only charged $115 or something like that to clean the internals and fix the focus, etc. He was very happy with the result.
08-01-2010, 11:20 AM   #3
philbaum's Avatar

Join Date: Oct 2007
Location: Port Townsend, Washington State, USA
Posts: 3,659
Just read your thread again, new lens, should be covered by warranty. If you're sure of your adjustment numbers, then send it in is my recommendation.

best wishes,

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calibration, focus, focus calibration, front, front back focus, k-mount, k20d, pentax lens, result, slr lens
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