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03-15-2018, 01:15 AM   #1
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Issues with SDM lenses

I've recently started having issues with SDM lenses on my K-3.

I have two lenses, the 50-135 and the Sigma 18-35.

The lenses occasionally just don't move when I half press the shutter, or press the AF button.

If I manually focus the lens sometimes it comes good, and starts to work again.

It seems like the lens isn't getting enough voltage and the motor can't over come the static friction. When it does move, it seems slower than it used to be.

If anything the Sigma lens seems faster / easier to get moving again.

Screw drive lenses work fine.

I've tried a number of batteries, and charged them fully, it doesn't seem to make any difference.

Any ideas?

Thanks.

03-15-2018, 01:30 AM   #2
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Maybe cleaning the electrical contacts on body and lens will solve the problem?

Last edited by nobody; 03-15-2018 at 02:32 AM.
03-15-2018, 01:31 AM   #3
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I have never had any such problem ( knock on wood )

but I have heard about this

does this article describe what you are dealing with:

Pentax SDM Failure Survey Results - Articles and Tips | PentaxForums.com

be sure to reviews the comments to the article

Last edited by aslyfox; 03-15-2018 at 03:02 AM.
03-15-2018, 01:47 AM   #4
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Hi alloneword, your DA* 50-135 is SDM, but your Sigma uses a different type of motor ( HSM ). As @nobody suggested, cleaning the contacts on both your camera and lenses would be a very good 1st step. Good luck.

03-15-2018, 01:51 AM   #5
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other thoughts

SDM to Screwdrive Conversions - Page 13 - PentaxForums.com

How To: Convert SDM to ScrewDrive + Video - Page 8 - PentaxForums.com
03-15-2018, 02:26 AM   #6
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Cleaning is the first step ... the second step is changing the SDM motor. The new series of SDM's are really good - just personal experience. If you feel the lens is not focusing well, go to the service.
03-15-2018, 02:41 AM   #7
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As has been suggested already, clean the contacts on both the camera and lenses first. It's worth cleaning all of the contacts and the mount ring, but for SDM operation pay close attention to the two gold-coloured contacts just inside the mount ring.

Also check that the two camera contacts are protruding the same amount. If I remember correctly, they're sprung. It's possible - unlikely, but possible - that one or both of them is stuck.

Good luck
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Last edited by BigMackCam; 03-15-2018 at 02:50 AM.
03-15-2018, 05:02 AM   #8
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sdm in my 50-135 died instantly
sdm in 16-50 - in the beginning it was not focusing on some occasions, than it stopped working altogether.
sdm in 55 has been squeeking for many years, but still working ok

repair costs are little more than 200$ (4000kc) here in CR and it takes 2 weeks

03-15-2018, 05:44 AM   #9
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The 50-135 can be converted to ScrewDrive, but you should verify that it isn't a problem with the body before you go to that effort. Does anyone have an sdm lens you can test with, or another body you can check the lenses on?
03-15-2018, 08:25 AM - 1 Like   #10
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If both the Sigma 18-35 and the 50-135 are having issues that points more to an issue with the body or the contacts, not the lenses since only the Pentax lens is SDM. Of course it could be both but that is unlikely.

As others have noted a good cleaning of the contacts on both camera and lenses is the first step.
03-15-2018, 08:43 AM   #11
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QuoteOriginally posted by jatrax Quote
If both the Sigma 18-35 and the 50-135 are having issues that points more to an issue with the body or the contacts, not the lenses since only the Pentax lens is SDM. Of course it could be both but that is unlikely.

As others have noted a good cleaning of the contacts on both camera and lenses is the first step.
My reason for asking about lenses is that the Sigma 18-35 has a history of poor focus across multiple brands. I didn't know if this was contributing to the problem. The 50-135 has a reputation for SDM issues as well. Given this I'd love to know if this was confirmed to be a body or lens specific issue before trying to dive in and solve it.
03-15-2018, 09:06 AM   #12
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QuoteOriginally posted by UncleVanya Quote
Given this I'd love to know if this was confirmed to be a body or lens specific issue before trying to dive in and solve it.
Agree. it is entirely possible the Sigma is having it's own (unrelated) issues and the 50-135 is having an SDM issue. It's not a good situation for testing because both of the lenses in question have a reputation for problems. Just not the same problem. Having another (known good) SDM lens to test with would be a good idea. After the obligatory contact cleaning.
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