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02-22-2011, 05:02 AM   #1
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Please explain the SDM failure issue

I experienced an SDM failure on my DA* 60-250 a while back that I was able to correct. I'm curious to find out if the issue I observed is what people here are categorizing as "the" SDM failure issue.

When my lens messed up I could not auto or manual focus the lens except closer to me when mounted on the camera...even with the camera off. With the lens off the camera the manual focus worked just fine.

Is this the issue people have been seeing or is it something else?

02-22-2011, 07:04 AM   #2
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Uh, are you sure that your camera's screw drive isn't giving resistance somehow?
02-22-2011, 10:57 AM   #3
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Adrian, please explain how you were able to 'correct' your SDM failure.
When the camera is off, a DA* lens will act like an MF lens anyway. This has nothing to do with SDM.
You can be sure that the SDM 'issue' isn't a made up fantasy - it's a relatively common loss of AF function in a DA* lens that was working previously. Sometimes there are warning signs (sluggish AF response when first operating the SDM, perhaps related to the time lapsed between usage, and/or requiring several AF engagements by the camera to try and 'kick-start' the SDM to working, for example) and sometimes there aren't.

Problem is, there's no way to tell which DA* has this fate. There are lots of happy DA* users out there who have never had a problem with their copies for a number of years now, never needing SDM repair, and others have had to repair theirs multiple times...
02-22-2011, 03:57 PM   #4
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You know I think I have read just about every post on DA*16-50 SDM issues. And it seems some people have multiple problems and others have not had any problems.

One thing I have not seen discussed is whether an individual uses AF-C or AF-S. Is it possible that using one or the other causes a different reaction in the lens? Or do I not understand how this works?

02-22-2011, 04:19 PM   #5
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The failure I experienced was one in which the manual focusing wouldn't even work when mounted on the camera body. It did not matter if the camera was turned on, had a battery in it, or anything...so long as it was mounted on the camera all the way.


QuoteOriginally posted by Ubuntu_user Quote
Uh, are you sure that your camera's screw drive isn't giving resistance somehow?
It is my belief that the camera's screw drive was giving the slightist amount of pressure on the lens' screw drive mechanism. The reason I suspect this is because when I pressed the lens release button and still had the lens on the camera body, both the SDM and the MF worked just fine.

After finding this out I took a small screw driver and gave the lens mechanical AF system a slight turn, re-mounted the lens and everything worked as I would expect it to.

This was back in November. After I started this thread someone posted a link in another thread to this thread https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/130429-diy-sup...or-repair.html which basically describes how I "fixed" my SDM failure issue.


I'm not trying to say that this is everyone's issue. I'm just wondering how many people are seeing an issue with the SDM function and it turns out to be something like this?

The failure didn't happen just by me putting the lens on one day. I had it mounted and over the course of an hour or two of using it the function started to die by not allowing focusing past ~5 feet.


Sorry for the long winded reply.
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