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09-11-2008, 05:39 PM   #1
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Sigma 10-20mm w/ K20D oddity

I noticed that images were very soft to the point of looking out of focus when using the Sigma 10-20mm on the K20D. Today I shot several test pics in raw and jpg and thought i had a focus problem. Now I'm not sure what I have. all pics shot with the same settings and 100% crop, except, pic 1 was shot 10mpx jpg, pic2 was 14mpxjpg and pic 3 was raw and converted to jpg 14mpx. Anyone else with this lens and K20D that is experiencing this? The 10mpx jpgs are fine, but at i4mpx raw or jpg they are terrible. Suggestions/Comments?


Last edited by ivoire; 04-18-2009 at 09:23 AM.
09-12-2008, 09:10 PM   #2
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That is really odd...
When you say 10mp are you talking K10D or K20D set to 10MP?
My Sigma works really well on my K100D super, K10D and K20D, but it does produce richer colors in my 6MP camera..Likely the settings I use though....
09-13-2008, 05:21 AM   #3
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I never had this problem on the k10d, but it started showing up on the k20d. thats how i got the idea to try it with k20d set to 10mpx jpgs. I think i'll have to send it in for service since its still under warranty. just a nuisance since its my 'money making' lens and business has picked up. may have to use it in 10mpx jpg mode until thanksgiving/xmas when biz halts for a few of weeks
09-13-2008, 08:19 AM   #4
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Could it be a bf/ff issue? If so the K20D will let you tune it in for this. Have you tried manual focus?

09-13-2008, 08:55 AM   #5
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I downloaded some bf/ff cards and did the test. the results were fine at center of focus with equal falloff as per the test instructions on front and back. thats when i thought of the 10mpx jpg test. You would think 10mpx or 14mpx results would be the same, but the photos indicate otherwise. I'll try cleaning the lens and body contacts and do a reshoot. If it happens again, will return it for service in late november. Thanks for the suggestions. For anyone else who suspects focus problems, heres a link for test cards you can print and instructions on how to conduct the test:

PART-1. Autofocus Adjustment for the Pentax K20D, Custom Setting No 35 - Digital Photography - Zimbio
09-13-2008, 10:06 AM   #6
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I should have followed the KISS formula, which would have eliminated several hours of work. After cleaning the lens and camera contacts (even tho to the naked eye they looked fine), i noted quite a bit of 'black stuff' on the q-tip. Tested the lens again and no more fuzzy pics at 14mpx. I can only guess that the randomness of the pic quality was due to the dirt/gunk on the contacts...... live 'n learn
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