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08-07-2011, 05:20 AM   #1
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FA 31mm infinity focus

I'm having a problem with my 31mm. I did AF adjust with my K-5 and I found it needed an adjustment all the way to 10 (I forget if + or - at this time). The problem I'm having is that when trying to auto focus on something at infinity it won't lock on sometimes. The lens will focus to infinity as per the distance scale. I'll have to switch it to manual focus to take the shot. Is this a problem that is a result of the AF adjustment?

08-07-2011, 06:07 AM   #2
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Does this only occur with your FA31, not other lenses? Any AF system can have trouble locking onto infinity if infinity doesn't have enough contrast for the AF to see.
08-07-2011, 06:18 AM   #3
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I too see this occurring from time to time with my K20 - and just about any lens, including my 31. If the camera does not sense that AF lock has been achieved, even though the lens has been run out to infinity and its an infinity image you are trying to take, the body will not allow the image to be taken.

In some way, I guess the K5's AF has been improved, but still not all there yet, which is some what disappointing (I have a K20 and pondering an upgrade). I do have to say that at times I wonder what the AF algorithm is trying to do. I was out walking up to a vantage point, decided to take a picture of a cactus up on the hillside in the late afternoon - plenty of light, high contrast - and still no way to achieve lock. So the bottom line is - it all has to deal with the image you were trying to take and the lighting conditions at the time, along with what the camera was sensing.

08-07-2011, 06:53 AM   #4
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Hmm. The only other AF lenses I have are the 18-135 WR (which I don't use that much anymore) and the 10-17 fisheye which always focuses very well. I guess I'll have to do some in-depth tests with the 18-135 and the fisheye. Thanks for the info, guys.

08-07-2011, 11:30 AM   #5
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Did it try to AF fast infinity? If so, maybe your FA31 cannot hit infinity.
08-07-2011, 10:56 PM   #6
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Can you manual focus to infinity? If you can't then its a lens problem. If you can, then its a camera problem.
08-07-2011, 11:20 PM   #7
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I had the very same issue on my old GX20 when 31ltd was mounted. Sometimes it seemed like camera thought the focus point was pass lens' infinity. This behaviour stopped once I readjusted the AF. So yes, I believe it's result of you adjusting the AF setting. I'll bet if you lower it your lens will focus on infinity without problem. Question will be how accurate it will be at shorter distances...
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