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03-21-2011, 10:06 AM   #1
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Sigma 10-20mm/4-5.6 not recognized by K-5

Hi, I have a weird issue and would like to know if anyone else has encountered it.

When I mount my Sigma 10-20/4-5.6 DC on the new K-5 (firmware 1.03), the camera asks for the focal length, then shows F-- instead of aperture. When I release the mount lock a bit and slightly push or move the lens sideways , I sometimes get the camera show aperture values in AV mode (but the values have nothing to do with reality - I can choose f1.2 if I like). Also the autofocus never works - the motor does not even try to rotate. The lens has connection to the AF axle, because focus ring is loose when AF is off on K-5 and heavy when AF is on.

The Sigma works just perfectly on my older K200D. Also other lenses like Tamron 90mm Macro and Pentax 35 Ltd both work fine on both bodies.

I have cleaned the contacts of the Sigma and the K-5. I can see no mechanical differences between the K-5 and K200D mounts. I'm wondering if the K-5 does not communicate with the chip(?) within Sigma, and so does not recognize the lens at all.

Could some K-5 owner with the older model of the Sigma 10-20 confirm if the combination should work OK?

I guess I'm going back to the camera store to test the Sigma with another K-5 (if they happen to have one).

03-21-2011, 10:33 AM   #2
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Is there any chance the aperture ring is moved out of the "A" position? Perhaps the old camera is set up to accept that whereas the new one is not.
03-21-2011, 10:37 AM   #3
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QuoteQuote:
enoeske Is there any chance the aperture ring is moved out of the "A" position? Perhaps the old camera is set up to accept that whereas the new one is not.
There is no A-ring on the 10-20 4-5.6.
03-21-2011, 11:33 AM   #4
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I have both the K5 and 10-20 (4-5.6) and have not had any issues. Hope you work out the problem.

03-21-2011, 12:28 PM   #5
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When I first got my Sig 18-200 it would do this, but turning off and re-mounting the lens made it go away.
03-21-2011, 12:52 PM   #6
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Clean the contacs
03-21-2011, 01:17 PM   #7
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Thanks for the helpful suggestions. I already had cleaned the contacts on the body and the lens, also remounted several times with shutting down and removing batteries. I also did the factory reset.

I'll do the cleaning once more, this time with isopropyl alcohol. Then it is off to store tomorrow. It is good to know K-5 should work with Sigma 10-20 without problems (thanks frogfish!)

EDIT: cleaning did not help. But I noticed I can make the electrical contact by pulling the lens heavily against the camera body. There is no play between the lens and camera, so there must be a tiniest amount of gap between the contacts. Needless to say, this combo is unusable as it is now, so I'll make a trip to the camera store.

Last edited by lockheed; 03-21-2011 at 02:07 PM.
03-21-2011, 02:03 PM   #8
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My K5 and Sigma 10-20 talk to each other without any problems.
Hope you can sort it out.

03-21-2011, 04:58 PM   #9
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I had similar problem when my Sigma 24-70 f/2.8 had problem. I ended up with new replacement from Sigma (after several other issues FF, focus-hunting, etc).
03-26-2011, 03:52 PM   #10
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Been using my K-5 (Software V1.03) & 10-20mm Sigma a lot this afternoon = no problems
03-26-2011, 05:28 PM   #11
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I've had no problems with my Sigma UWA lens either or any of the other lenses.
03-27-2011, 02:53 AM   #12
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I took the K5 and Sigma for service on Tuesday, and the contact fault was confirmed on Friday. Hopefully some adjustments can be made on the body, will know more on Monday. Yet another week without K5, the first body took 3 weeks to replace

The current body also has occasional problem with the horizon being some 10 degrees skewed to left, like the floating sensor getting stuck in wrong position. I just hope the repair shop can reproduce the problem too...

EDIT 2011-03-29:
Just to close this thread, an update: I got the K5 and Sigma 10-20 back from repair shop, and it is working now. The service report says that a circuit/connection was repaired and the sensor has been adjusted. I hope this is the end of my K5 troubles at last.

Last edited by lockheed; 03-29-2011 at 05:10 AM.
10-28-2011, 08:09 PM   #13
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Hope so, I recently got my K5 and am waiting for the sigma 10-20mm f4-5.6
10-29-2011, 06:44 AM   #14
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Occasionally experienced same problem with my Sigma 10-20.. K5 shows F-- and ask for focal length input, but imo that's just a minor problem since by pushing the lens a lil' bit firmer to the body solves the problem. Never happened before with my old K20D though
10-31-2011, 08:27 AM   #15
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QuoteOriginally posted by silverelantra Quote
Occasionally experienced same problem with my Sigma 10-20.. K5 shows F-- and ask for focal length input, but imo that's just a minor problem since by pushing the lens a lil' bit firmer to the body solves the problem. Never happened before with my old K20D though
same here
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