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12-13-2012, 11:54 AM   #1
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Pentax K-30 + Sigma 18-125, AF does not work


Received my first proper DSLR, the Pentax K-30 today along with Sigma 18-125 F3.8-5.6 HSM lens. Went according to the manual and put the camera together. Everything was working absolutely fine. Then, I switched the lens into the MF position to try out how the manual focus ring feels. The camera display changed into the MF mode at the same time. Now, the problem is that after i switched the lens switch back into the AF position, camera is still in the MF mode. There is no response from the lenses AF motor.

What might have gone wrong? I have tried removing the battery and resetting the camera. Also removed the lens, cleaned the contacts to no avail. Also turned the camera on without the lens, and then turning the body switch to all the locations without any effect (still showing MF). I've also updated the firmware to the latest version without any help.

At present I have no possibility to test with another lens or have the lens tested on an other pentax body.

12-13-2012, 01:34 PM   #2
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Location: Brisbane, Australia
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It may be silly, but is the camera set to AF.C or AF.S?

You need to set both the lens and camera to AF.

Hope it may help.
12-13-2012, 03:04 PM   #3
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Yes, indeed the camera body switch is set to AF.S. Changing the position of the switch has no effect on the focus mode. Initially when i set the lens to MF, i did not set the camera switch to MF. However, the lcd showed that camera had changed to MF and it was hilighting focus with beep/red marker.
12-19-2012, 09:58 AM   #4
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Short update on the situation. The autofocus on the sigma lens does not work on an other Pentax body either, so the lens is at fault. I left the lens in for service and they hadn't heard of a similar case happening before. I'll update the thread once I get the lens back from service, will probably take 2-3 weeks due to part ordering and holiday season.

01-27-2013, 10:35 AM   #5
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The electronics have been changed and the lens is working again. The service also tuned the autofocus to my body, since after adjustment with their own pentax body there was some severe front focus at the telephoto end. After that the wide end was front focusing, but -7 fine adjustment solved that while still keeping the rest of the focal length in check.

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