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08-08-2010, 03:31 AM   #1
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K7 does not recognize Sigma lens (sometimes)

Strange thing as it only happend 2-3 times on a trip, so I could not make more tests.
My Sigma 18-50 / 2.8 normally works fine on Pentax K7, but recently the camera started with "input focal length", not knowing anything about the lens (no aperture range etc.), so I did not have: aperture settings, AF etc..
One day later everything was ok again, and later it came up again....

There is still warranty on camera and lens, but the point is that I can't show the effect as it is very rare. I don't even know, if the camera or the lens is to blame for it (as my other lenses are all old MF-Pentax). After all - at the moment everything is ok again.

So my question is, if anybody else encountered this or heard about it? I could not google anything sensful on this.


P.S.: There was no lens change, so I don't think it is an contact issue. I even once had a jittering between "AF" and "MF" in the display, which I think is an indicator for "loosing the lens".

08-08-2010, 03:40 AM   #2
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Has the aperture ring slipped off A? That happened to me once, and it was that the aperture ring was not on the A setting.
08-08-2010, 04:24 AM   #3
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aperture ring

no, not he case, there is no aperture ring with this lens (and therefor no chance to set the aperture manually when the lens is not recognized.)

08-08-2010, 07:07 AM   #4
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Yeah my sigma 18-50mm ex 2.8 macro has no aperture ring either. But never came across such an issue with my K-7

08-08-2010, 08:20 AM   #5
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I have a Sigma 70-300 APO on K-7 body. Also happened to me what you're descibing. The body would not recognise the lens, the aperture indicator stayed at F-- and AF was not working (it was like having a MF lens). I sent the lens to service and came back ok. The shop didin't tell me what was the cause. Now, 6 months later after being serviced it started acting up again, but like you say it's not constant and after moving the lens on the mount it becomes ok...

You should try to clean the contacts on the mount (both body & lens) with an eraser (or some special cleaning stuff that you find on the market) and see if that helps.
08-09-2010, 07:03 AM   #6
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My 10-20mm Sigma does the same on my K-7 for just literally a split second when I turn the camera on and then it gets recognized and all is good.
08-09-2010, 03:13 PM   #7
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I had the same issue with a Sigma 105 macro lens. Sigma uses a terminal block for the contact pins below the mounting base and mine was shifted a hair over so the pins were not dead center in the openings. Plus the terminal block was a bit loose inside which probably lead to the shifting. I had it shifted to direct center and of course made sure the contacts were clean. Problem solved.
08-09-2010, 05:40 PM   #8
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Sounds like your contacts are not fully connecting but there is also a chance that your contacts are shorting out. If a simple clean does not work then I would send it in for warranty. You do not have to reproduce the error, just explain to the service center.

08-09-2010, 10:44 PM   #9
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QuoteOriginally posted by ulrich Quote
There is still warranty on camera and lens, but the point is that I can't show the effect as it is very rare. I don't even know, if the camera or the lens is to blame for it (as my other lenses are all old MF-Pentax). After all - at the moment everything is ok again.

So my question is, if anybody else encountered this or heard about it? I could not google anything sensful on this.
Contact Sigma support, before your warranty runs out.

I had the same thing happen to me—in the middle of a graduation shoot—with my Sigma 28 f/1.8. One of my favorite lenses. But suddenly it just stopped communicating with the camera. I could not control my settings the normal way, and in any case I didn't at the time know whether the problem was with the lens or the body. I think I suspected the body, actually. Fortunately I had another body and another lens and I was able to keep shooting.

After I got home, I did some research. Might even have posted a question like yours here in this forum. Anyway, I found reports from other users who had had similar things happen to them. I called Sigma. The tech support guy was a bit skeptical—which considering the uncertainty of the issue, isn't too surprising—but suggested that I send the lens in. I did. Not sure if they fixed it or sent me a new lens. I didn't record the serial number on the lens I sent in. That was about 2 years ago. Not a single problem since. And it's still one of my favorite lenses.

08-09-2010, 11:50 PM   #10
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Thank you

Thank you all for the posts. This all sounds that its the lens (hard to believe that its the contact, as during my 3 weeks trip the lens was permanently mounted).
Warranty is still more than 1.5 years, so I think I will send it back to Sigma.

08-09-2010, 11:54 PM   #11
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I think this might be a fragility with the K mount in general, I had a DA limited present this exact behavior right out of the box, nothing is wrong with my camera though, I think some lenses might just have a bad mount or connection
08-26-2010, 09:29 AM   #12
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I suddenly had a similar problem on my K20D w/ a Pentax 18-250 3.5 -6.3 len. I received an error message (F_ _ _ , actual message on display) on the Aperture display. After research online, the suggested options were 1) reset the camera from the menu, 2) take the battery out for 15 minutes 3) check to see it the Aperture ring was on "A" and 4) check to see if the "Using Aperture Ring" option in the "Custom" Menu was set to "Permitted" to allow "Pictures to be taken even when the Aperture Ring position is other than in "A" mode".
None of these worked for me, think I have bigger issues but, # 4, might be worth checking for your problem.
08-26-2010, 10:27 AM   #13
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The most probable reason for this is bad contact of lens and body.
Try to slightly rotate lens inside bayonet. You may hear some sort of click and get your lens working again.

Had the same problem with Sigma 18-50/2.8 EX DC Macro and K10D.
The lens got slightly overrotated inside bayonet.
08-27-2010, 12:52 AM   #14
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I hit this issue several times with my Sigma 105. Never hit it with any other lens, although occasionally I did get some random aperture reading when using non A lenses
08-28-2010, 07:34 PM   #15
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I had that problem with a sigma lens on a ist dl after firmware upgrade. I stoped by sigma with the lens and camera and they adjusted something for me and it worked fine after that. They have great support. they did it while I waited In there lobby.

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