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12-04-2011, 11:33 AM   #1
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Autofocus issues 50mm with new K5

I recently purchased a new K5. I have there different lenses. Two of the three work fine; however, the 50mm SMC FA 1.4 will not autofocus on the K5. It works well on my K10. My other lenses work on the K5.

I can hear the autofocus motor running, but it won't take any pics. Works well on manual focus.

Any ideas as to what could be the problem?

12-04-2011, 01:02 PM   #2
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What are the other two lenses?

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12-04-2011, 02:00 PM   #3
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The two lenses that work are: Pentax SMC DA 18-55mm kit lens and Tamaron DI 70-300mm

Thanks in advance for any insight you can provide.
12-04-2011, 03:24 PM   #4
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You first said it was an AF problem, but then you said it won't take pictures. That could well be something entirely different. Could you describe in more detail what is actually happening?

12-04-2011, 07:35 PM   #5
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It will take pics with manual focus, but not when asking it to autofocus. The motor tries to autofocus but never locks in enough to allow for a picture. Sorry for any confusion. I appreciate your trying to help.
12-04-2011, 07:38 PM   #6
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Have you tried to AF on a high contrast object, something with clear edges of colour/contrast? Or are you shooting a backlit scene maybe?
12-04-2011, 07:56 PM   #7
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Have tried a variety of lighting situations and photo subjects.

Here is an interesting twist. If I focus on an object using manual focus, get it in focus manually, then switch back to AF, I can take a pic. When on AF it will take a pic if I have it in focus by manually focusing before moving switch to AF. Hmmm. . .
12-04-2011, 08:13 PM   #8
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You are talking about the FA 50mm 1.4 and not the DA*55mm 1.4??

12-04-2011, 08:20 PM   #9
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I don't have issues AF with my fa 50. Some things to test:

Does this occur at any aperture setting or only at 1.4? Perhaps it is due to thin depth of field, so try smaller aperture.
Is this occurring indoors in dim light? Try outdoors in daylight?
Clean the contacts on the lens.
12-04-2011, 08:32 PM   #10
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I will try a greater variety of fixes tomorrow. How would you recommend cleaning the contacts on the lens? It is the FA.
12-04-2011, 09:44 PM   #11
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I would start by just wiping them off with a lint free cloth. Perhaps add a tiny bit of alcohol to the cloth.
Don't use a method that will contaminate the lens with dust particles, and be sure to blow it off with a rocket blower or similar? before reinstalling on the camera.
12-05-2011, 02:31 AM   #12
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I use a teflon pencil eraser to clean contacts, followed by a dust-off. No problem.
12-05-2011, 09:15 PM   #13
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Woo-hoo!! After lots of agonizing, wondering, posting and cleaning, I noticed a bit of debris located in a little hole just to the right of the lens contacts. Got the debris out and it works like a champ. Thanks to all for the advice to clean. Never would have found the pesky particle without it. Time to take pics!!!
12-05-2011, 09:56 PM   #14
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Good deal!
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