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04-29-2009, 06:46 PM   #1
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Anyone else have this DA* 50-135mm problem?

After not using the lens for a while, I take it out of it's bag, and connect it to the camera, and it won't auto focus. I turn the focus ring back and forth a bit, and then try auto focus, and it does so grudgingly, and intermittently. I have to operate the auto focus repeatedly until finally it starts working reliably. It behaves as if the SDM motors are "frozen" and have to be worked in a bit before they start responding.

This happens every time I put on the lens and it has been sitting for more than a few days. To head off the inevitable questions, here are some conditions:

-The lens is always stored in its bag, indoors, in an air-conditioned room.
-It has never been damaged or even bumped.
-The contacts are very clean.
-It does this on the k20d
-No other lens I own has AF problems. Only the SDM on the DA* 50-135.
-I have the latest k20d v1.03 firmware
-The lens is attached properly

I guess I am just not meant to have an operable DA* lens. First 3 defective DA* 16-50's and now this!


Last edited by PentaxPoke; 04-29-2009 at 06:53 PM.
04-29-2009, 07:07 PM   #2
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QuoteOriginally posted by PentaxPoke Quote
After not using the lens for a while, I take it out of it's bag, and connect it to the camera, and it won't auto focus. I turn the focus ring back and forth a bit, and then try auto focus, and it does so grudgingly, and intermittently. I have to operate the auto focus repeatedly until finally it starts working reliably. It behaves as if the SDM motors are "frozen" and have to be worked in a bit before they start responding.

This happens every time I put on the lens and it has been sitting for more than a few days. To head off the inevitable questions, here are some conditions:

-The lens is always stored in its bag, indoors, in an air-conditioned room.
-It has never been damaged or even bumped.
-The contacts are very clean.
-It does this on the k20d
-No other lens I own has AF problems. Only the SDM on the DA* 50-135.
-I have the latest k20d v1.03 firmware
-The lens is attached properly

I guess I am just not meant to have an operable DA* lens. First 3 defective DA* 16-50's and now this!
I had that happen while I was *trying* the lens at my local camera shop. The shop is great and its not their fault. But the shops DA* lens have been sitting for some time, at least that I know of. So I was thinking of buying the DA*50-135mm and tried it out. At the shop sometimes it would focus, sometimes not. The sales man got it going, gave me the camera I tried and nothing, gave it back to him he gets it to go after a few tries and gives it back to me, it worked after some time of playing like that... well I decided to buy a kit lens ver II, and cover it when it rains. I was not taking a chance with all this bad news I have been reading of late. You know if Pentax gave at least 3 years of warranty like everyone else I would have bought it. But one year, nope not me, thats when it goes bad after one year. My Sigma 10-20mm EX came with 4 years of warranty, Tamron 6 years... I can see with the regular DA lens one year, but a DA* premium lifetime lens....
04-29-2009, 07:11 PM   #3
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Mine sometimes exhibits the same behaviour. I have found that dismounting and remounting the lens is the most reliable way to get it going. I think the contacts may not be protruding as much as they should, but I am not ready to ship it out for weeks for fixing. We have a two year warranty here in Canada, so I'm going to wait until nearer the end of the warranty period.
04-29-2009, 07:58 PM   #4
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I had a similiar experience recently with my 50-135 after it sat for most of the winter. In my case cleaning the contacts and remounting did not work. While it focused fine in manual mode the auto-focus no longer worked. I sent it back to Pentax and instead of repairing it they just replaced it for me. The new lens works really well so far.

04-29-2009, 08:36 PM   #5
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had it happen with mine, same exact thing. eventually the SDM failed and it was sent to pentax and replaced (sent it before 1 year warranty was up)
04-29-2009, 09:17 PM   #6
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Thanks for the advice all. My warranty expires on May 19 so I just boxed up the lens to ship off to Pentax service.

/rant on

Why is it that I am now having to ship back my fourth DA* lens? I feel like I need to start adding a "shipping costs" line item to my lens budget whenever I buy a Pentax lens. If I knew then what I know now, I would have passed on the whole DA* hype and got the equivalent lenses from Tamron for less money and 6x longer warranty. I was under the impression that the "*" meant something good. Maybe the "*" is not a "star" but an asterisk that means: "buy this lens at your own risk."

/rant off
04-29-2009, 10:53 PM   #7
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It's happened to mine twice. Both times I pushed back the inner panic, carefully cleaned the contacts on the camera mount, including the inner SDM/PZ contacts, and those on the lens. Re-mounted the lens and it worked fine again.
04-29-2009, 11:57 PM   #8
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QuoteOriginally posted by Venturi Quote
It's happened to mine twice. Both times I pushed back the inner panic, carefully cleaned the contacts on the camera mount, including the inner SDM/PZ contacts, and those on the lens. Re-mounted the lens and it worked fine again.
Didn't work for me. As a last attempt, I cleaned the contacts, mount rings, etc. with microfiber cloth and a mild cleaning solution. I could darn well blind myself from the reflection coming off the spotless contacts, and the K-mount ring. No difference. I am sure the intermittency is in the SDM motors themselves. Otherwise, why would I have to "jump start" the motors by spinning the focus ring manually in order to get them to move?


Last edited by PentaxPoke; 04-30-2009 at 12:03 AM.
04-30-2009, 06:23 AM   #9
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Happened to me too. Used to flip the AF/MF switch on the lens back and forth a few times and the AF would work. This is no longer the case. I was transferred a third party warranty (SquareTrade) so I will be making a claim. Hopefully all goes well as this is my favorite lens.
04-30-2009, 06:55 AM   #10
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QuoteOriginally posted by PentaxPoke Quote
Thanks for the advice all. My warranty expires on May 19 so I just boxed up the lens to ship off to Pentax service.

/rant on

Why is it that I am now having to ship back my fourth DA* lens? I feel like I need to start adding a "shipping costs" line item to my lens budget whenever I buy a Pentax lens. If I knew then what I know now, I would have passed on the whole DA* hype and got the equivalent lenses from Tamron for less money and 6x longer warranty. I was under the impression that the "*" meant something good. Maybe the "*" is not a "star" but an asterisk that means: "buy this lens at your own risk."

/rant off
Now that they have almost doubled the price of the lens, they had better start shipping lenses that are flawless as well. Almost 2K for that lens is too high for a lens that odds are is going to crap out after a short service life.
04-30-2009, 07:29 AM   #11
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I have a quick question for you guys. Do any of you use the batterygip with you cameras? I have this lens had it for around 7months have not run into a problem yet. I always shoot with the battery grip and two batteries. I'm just curious if the sdm prefers the extra juice? I'm wondering if Pentax power system just does not have enough juice to effectivly power these lenses and in turn actually stresses the motor overtime to the point were they eventually fail.

Just a thought.
04-30-2009, 07:34 AM   #12
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I always shoot with a grip, not so much for the juice aspect, but for me it is more of a balance issue. With 50-135, K10 or 20 are both too small and too light, and my shot tends to come out with slightly different angle than anticipated.
04-30-2009, 07:45 AM   #13
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QuoteOriginally posted by GnusMas Quote
I have a quick question for you guys. Do any of you use the batterygip with you cameras? I have this lens had it for around 7months have not run into a problem yet. I always shoot with the battery grip and two batteries. I'm just curious if the sdm prefers the extra juice? I'm wondering if Pentax power system just does not have enough juice to effectivly power these lenses and in turn actually stresses the motor overtime to the point were they eventually fail.

Just a thought.
The camera only uses one battery at a time. You don't have twice the current with the grip.
I think this is a situation where they have put a high failure rate component into the lens, and the customers are now seeing the result.
04-30-2009, 08:33 AM   #14
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I have a relatively new DA*50-135 (B&H got it as part of a shipment in March), and what I've noticed is that the SDM focusing is rather slow and pokey compared to the version I tried in a local store (which was older). No difference after the 1.01-1.0.3 firmware update in my K20D, either. After a month of moderate use it hasn't failed to focus, but it's basically glacial compared to even a screw-drive equivalent.

Of course, the last SDM-type lens I had was the Canon 70-200 f/4 L, which was a comparative speed demon, even when the AF on the body was hunting. Plus, I rarely used it, and once after nearly 2 years of sitting (the rubber grips had started to go white!) the motors would still zip right up, nice and tight.

I wasn't terribly impressed with the Pentax 17-70 SDM and got the Sigma (while louder, it is faster and quite crisp), and I really wonder why it seems I'm "expecting too much" from this now $1700 CDN lens! (If I had paid that price, I'd expect it to at least equal an "L series" in performance.)

Frankly, I think Hoya/ Pentax should hold these DA* lenses to the same QA and standards that the Limiteds go through. These are modern "pro level" lenses in spec and cost, and should act like it *and* stay that way.
04-30-2009, 09:30 AM   #15
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QuoteOriginally posted by GnusMas Quote
I have a quick question for you guys. Do any of you use the batterygip with you cameras? I have this lens had it for around 7months have not run into a problem yet. I always shoot with the battery grip and two batteries. I'm just curious if the sdm prefers the extra juice? I'm wondering if Pentax power system just does not have enough juice to effectivly power these lenses and in turn actually stresses the motor overtime to the point were they eventually fail.

Just a thought.
I have the grip, but set the camera to use the grip battery first (one battery at a time). You just gave me an idea. I'll mount the 50-135 and if it acts up do nothing except switch the battery usage to "both" and see if it magically fixes the focusing.
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