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07-06-2015, 06:37 PM   #1
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DA*50-135 no focus

A week and a half ago B&H had a great sale on the DA*50-135 and I jumped on it. I've been wanting this lens to compliment my DA*16-50. I put it on my K3 and it focuses a few times and then nothing. I took it off and put the DA*16-50 on and bang, bang, bang... focused and fired every time. Put the 50-135 back on and push to focus and take a picture and nothing. I get the red dot on the screen but no audible signal that focus has been acquired and no firing of the shutter. If I switch the lens to manual focus I can focus, get the audible signal and the shutter will fire. Switch the lens back to autofocus and nothing..... Do I have a DOA lens or might I be doing something wrong? The DA*16-50 works great but not the brand new DA*50-135. I still have about three weeks to return it to B&H but I want to make sure I'm not doing something wrong.


Thanks, Bob

07-06-2015, 07:02 PM   #2
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Check all contacts on the lens. Are they clean, raised, and undamaged in comparison to your 16-50? Do you have "Auto" focus selected on the lens? Otherwise, suspect you may have a bad lens that is damaged before or during shipment. Hope it is a simple fix.
07-06-2015, 07:08 PM - 1 Like   #3
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Sounds like SDM failure to me. Back to B&H it goes.
07-06-2015, 07:12 PM   #4
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QuoteOriginally posted by Sandy Hancock Quote
Sounds like SDM failure to me. Back to B&H it goes.


I suspect that you're right but it breaks my heart. I've sooo wanted this lens and there really isn't another option. I was hoping the SDM was a thing of the past but maybe not. I'll give it another try though and see if the second one is OK. Does the forum keep records of the serial numbers of lens that have SDM failure?



07-06-2015, 07:28 PM   #5
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You would need to enter the serial number and issue yourself at SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM Serial Numbers - Pentax Serial Number Database - PentaxForums.com
07-06-2015, 07:36 PM   #6
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My DA*50-135 is still going strong after three years of solid semi-commercial use. Early on though I was concerned that the SDM was dying, but it responded to the occasional warm-up involving some rapid manual focussing from infinity to MFD and back.

Definitely make sure the SDM contacts are clean too.

Then there is always conversion to screw drive. I hacked my DA*16-50 two years ago and it continues to be one of my most reliable work horses.
07-06-2015, 07:44 PM   #7
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QuoteOriginally posted by crewl1 Quote


Thank you.... interesting reading!

---------- Post added 07-06-15 at 09:46 PM ----------

QuoteOriginally posted by Sandy Hancock Quote
My DA*50-135 is still going strong after three years of solid semi-commercial use. Early on though I was concerned that the SDM was dying, but it responded to the occasional warm-up involving some rapid manual focussing from infinity to MFD and back.

Definitely make sure the SDM contacts are clean too.

Then there is always conversion to screw drive. I hacked my DA*16-50 two years ago and it continues to be one of my most reliable work horses.


I see that others have tried this "warm up" trick. I will try tomorrow and see but still.... brand new... it should work. Might return it and say the hell with it and buy the FA 77mm....

07-06-2015, 08:04 PM - 1 Like   #8
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QuoteOriginally posted by woodywesty Quote
Thank you.... interesting reading!

---------- Post added 07-06-15 at 09:46 PM ----------





I see that others have tried this "warm up" trick. I will try tomorrow and see but still.... brand new... it should work. Might return it and say the hell with it and buy the FA 77mm....

Before you do that, how much do you love your 16-50? The 50-135 is better. I would give a second copy a shot. I had both, but sold the 16-50 cause it didn't curl my toes like my 50-135 does.

07-06-2015, 09:00 PM   #9
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QuoteOriginally posted by woodywesty Quote
but still.... brand new... it should work. Might return it and say the hell with it and buy the FA 77mm....

I think it's too early for that. Although I am a huge fan of the FA77, there are times when the DA*50-135 will just keep on delivering the goods if you shoot events, especially outdoors in the weather. There are also times when silent focus is a real bonus.

My first DA*55 was stone dead right out of the box (and it has no screw-drive mechanism to hack into). Its replacement is an absolutely spectacular lens which I would not be without.
07-07-2015, 01:54 AM   #10
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I would just exchange the lens. DOA SDM still happens, unfortunately, but chances of it happening twice are slim.

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07-07-2015, 06:11 AM   #11
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QuoteOriginally posted by jayman_1975 Quote
Before you do that, how much do you love your 16-50? The 50-135 is better. I would give a second copy a shot. I had both, but sold the 16-50 cause it didn't curl my toes like my 50-135 does.


I do like the 16-50 but the 50-135 isn't curling my toes but it is making me grit my teeth!



---------- Post added 07-07-15 at 08:14 AM ----------

QuoteOriginally posted by Adam Quote
I would just exchange the lens. DOA SDM still happens, unfortunately, but chances of it happening twice are slim.



That's what I'm going to do. I suspect that there is a quality control issue with the contacts, their fabrication and assembly. A good manufacturing engineer could identify the problem in a week and be done with it. What a shame this has gone on for so long. Still, I'm going to give it another try and hope the next one is functioning OK.
07-07-2015, 06:40 AM   #12
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DOA is a less worrisome issue to me. Electronics tend to be DOA or work well for years I wouldn't sweat it. It could be a simple AF/MF switch issue. Return it and get another.

---------- Post added 07-07-15 at 09:42 AM ----------

Btw my 50-135 was dead SDM (known at purchase time) and the rapidmanual focus trick worked. It is still going strong.
07-07-2015, 05:42 PM   #13
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I jumped on that deal as well and I bought a 50-135 as well. So far mine is working flawlessly and I plan on putting it through all tests in the next few weeks. I have never had any issue returning anything to B&H ever in over twenty years.
07-07-2015, 06:58 PM   #14
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QuoteOriginally posted by Scorpio71GR Quote
I jumped on that deal as well and I bought a 50-135 as well. So far mine is working flawlessly and I plan on putting it through all tests in the next few weeks. I have never had any issue returning anything to B&H ever in over twenty years.


It was a heck of a price that's for sure. I hope yours works well for many years. I'll call B&H tomorrow and get the process started to return the bad copy and get me another one....

07-07-2015, 11:41 PM   #15
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Here's a different view: Keep the faulty new lens (from B&H) and send it in to Pentax service under warranty repair if you are satisfied with its optical performance (e.g. lens element centering).

Now my story…
Back in 2012 bought a new K5 and Sigma lens as my first DSLR. About 3 months later I bought a new 50-135mm and FA 43mm from B&H. The 1st copy of the 50-135mm couldn't focus to infinity with my K5 (the pair were at opposite ends of the AF fine adjust tolerances). Exchanged the lens for another copy via B&H's excellent service. The 2nd copy improved the situation somewhat but still not sufficient. Being a major fan of B&H (since 1986) I didn't have the heart to continue dragging them into Pentax's manufacturing problem. So I contacted Pentax service and discussed the situation with them. They advised me to send all three 'under-warranty' Pentax OE items to them (K5, 50-135mm, 43mm). They calibrated the K5 body AF to nominal using a master lens, then adjusted each lens to satisfy AF Fine Adjust = 0. Received the whole kit back in about 3 weeks. Unfortunately, with in a week or two the 50-135mm failed to successfully complete focusing in Live View. So off that lens went to Pentax service again for SDM replacement under warranty.

The outcome…
To this date (knocking on wood my K5 and its respective lenses have been amazingly accurate in acquiring AF lock. Excluding the effects of the large central sensor size, I have not had difficulties with front or rear focus and very rarely have experienced focus hunting. Of course this outcome was the result of system calibration rather than SDM repair and the K3 already performs more reliably.
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