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10-05-2015, 06:00 PM   #1
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Sigma 10-20 stuck in manual focus

Before I send out my lens wanted to see if anybody knew of a way to fix this issue. I have a Sigma 10-20mm F4-5.6 EX DC that does not seem to want to work in auto focus anymore. I've tried it on my k-50 and k-3.

It worked fine and then one day I decided to try it on manual on the k-50. After that when I tried to put it back on auto I get a message to chose focal length on the lcd screen and it would not auto focus. I tried switching it to the k-3 and same thing.

I have tried taking the battery out and putting it back in, charged battery to full and tried still nothing. I have wiggled the AF MF switch thinking maybe it got stuck and nothing. This is the first real problem I've had and don't know of anything else to try any suggestions would be appreciated.

10-05-2015, 06:13 PM   #2
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I'd try cleaning the contacts on the camera body and the lens.It sounds like the camera is not communicating with the lens when you have to input the focal length.
10-06-2015, 06:02 AM   #3
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I have this lens, it has screw drive for the AF, with the lens off, turn the focussing ring and the screw coupling at the rear of the lens should rotate. As bcshriver11 says, cleaning the contacts usually helps, use a lens cloth or spectacle wipe.
10-06-2015, 08:14 AM   #4
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Tried cleaning the contacts, no luck. The screw coupling does move when it is off the body, looks like I'll be sending it out. But since I just use this lens for landscape and buildings using it on manual is not that difficult, maybe I should just live with it. Thanks for the help.

10-08-2015, 11:46 AM   #5
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Have you checked that the camera body works with another lens, the kit 18-55 would be ideal. When you mount the 10-20, rotate it in the anticlockwise direction to make sure it is locked onto the body. With some lenses locked onto the body, there is a tiny bit of rotational free play which might interfere with the alignment of the drive couplings. When any lens is fitted, the projecting screw drive coupling is pushed down flush with the mounting flange. The tiny pip in the centre allows this to happen without damage to the camera or lens. When you press the button to unlock the lens prior to removing it, the screw drive coupling is withdrawn below the flange surface. If you push down on the screw drive coupling with your finger, it should pop back up when you take your finger away, it has a weak spring. If all these tests fail and the body is working ok, then an electrical fault in the lens may fool the camera body into thinking that the lens is an early manual focus lens and disable the autofocus and ask for the focal length to be input.

---------- Post added 10-08-15 at 11:51 AM ----------

I forgot to ask if the aperture controls work as the lens does not have an aperture ring. The 10-20 is one of the most suitable lenses to use with manual focus as the depth of focus is so great, you could just use the feet/metre scale with no problems.
10-10-2015, 04:21 PM   #6
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Other lenses work fine on the body and the screw drive coupling does pop back out when pushed in by hand. I didn't notice before but the aperture controls do not work either, I will definitely be sending it out for warranty service.
10-11-2015, 10:41 AM   #7
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QuoteOriginally posted by KiloHotelphoto Quote
Other lenses work fine on the body and the screw drive coupling does pop back out when pushed in by hand.
Well, then there is a fault in the lens electronics that set the state of the mount contacts. Your first clue is the F---. That means that the camera does not detect the lens. With any luck Sigma service will get this fixed for you.


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10-11-2015, 12:33 PM   #8
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Hope the bill is not too high, the lens is worth repairing, my copy is amongst my five favourites.

10-12-2015, 07:54 AM   #9
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Just got the lens in March so I hope it's covered under warranty.
10-15-2015, 04:59 PM   #10
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Shipped the lens to Sigma on Monday the 12th and got it back working properly today the 15th. Have to say I am very impressed with Sigmas warranty service.
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