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02-12-2013, 02:24 PM   #1
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Noob question: Should any K-mount AF lens work on K-01?

I was operating under the assumption that any K-mount AF lens would work (as in AF should work) on the K-01. I mounted a Sigma 75-300mm AF f4.5-5.6 on the K-01, checked that the K-01 focus switch was on AF, and turned on the camera. No matter what (I took the e-dial for a spin), there is no sign of AF working, and the shutter won't activate to take a pic (even unfocussed). The screen just blinks with a red F--

Camera works fine with DA lenses -- I've tried the 40mm xs and 18-55 DA II

Is there some setting in the camera that I need to turn on/off? I don't think there's anything wrong with the lens 'coz it does the same with another Sigma zoom (I forget its specs). I am not looking for fast AF, just some indication of AF.

Thanks for a pointer or two.

02-12-2013, 02:30 PM   #2
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The short answer is yes. The long answer is that telephoto lenses (especially consumer zooms) are really slow to focus. Slow to the point where I can't recommend using them in AF mode.

Check your lens's contacts and try cleaning them to see if that fixes the problem. Also, make sure the aperture ring is set to "A".

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02-12-2013, 02:51 PM   #3
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You should also check to see if it the auto focus works on a different Pentax DSLR. I had a similar issue with an old Sigma AF lens on a K-r. Turns out it the A setting wasn't working properly.
02-12-2013, 03:14 PM   #4
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Original Poster
Thank you both. The issue was operator ignorance :-) I saw the A marking by the aperture ring but didn't realize its significance (I did look vainly for a MF-AF toggle) nor that I had to press a nub to get it to click.

The AF is indeed slow but there are occasions when it locks in extremely fast (perhaps when there aren't too many objects confuse it).

Last edited by harioharima; 02-12-2013 at 04:22 PM.

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