Tamron 17-50mm AF problem

tibbitts · 05-24-2014, 11:41 AM

I've been using a Tamron 17-50mm for about a year (lens was bought new) without incident on a K5, K5ii, and K200. The AF needed a substantial adjustment on both K5s, but otherwise there weren't any problems. On the day before a 2 week trip, I went to dust check the sensor, and, for the first time ever, the AF failed. Specifically, the lens seemed to intermittently disconnect electrically - it might rotate the barrel in one direction to focus, then the finder indicator would revert to MF, and then only intermittently switch back to AF if the lens was fairly forcibly rotated the tiny fraction of a mm that it could be rotated on the body while still mounted. Generally after mounting it would make one attempt to AF, then disconnect. The behavior was exactly identical on the K5 and K5ii. I tried the usual contact cleaning (with electrical contact cleaner), not that the contacts were apparently dirty, but it had no effect.

Throughout the 2 week trip (with the K5 and K5ii), through dozens of mountings/unmountings, AF behaved this way on both the K5 and K5ii. I tried AF periodically but no luck, which wasn't the worst thing ever, but mildly annoying. Exposure and all other functionality was good. Other AF lenses, Tamron brand included, worked fine with both bodies.

Upon returning, I tested the lens on the K200, and, just once, it behaved exactly as on the other two bodies. Then, after unmounting and remounting on the K200... it worked correctly. No wiggling of the mount had any effect. After repeated additonal unmount/mount cycles, it still worked. What's stranger, back on the other two bodies, same story... the AF is now working on all three bodies.

I'm wondering if anyone else has experienced similar behavior.

Adam · 05-24-2014, 04:01 PM

It could just be wear on the lens mount that caused looseness or just a poor electrical connection, hopefully it doesn't happen again!

rawr · 05-24-2014, 04:44 PM

I've not struck the same problem, but if it's the AF but nothing else, then it may be worth paying some attention to how the AF screw in the lens is mating with the body. There may be some movable grit or grime in the vicinity of the AF screw on the lens.

EarlVonTapia · 05-24-2014, 09:46 PM

Originally posted by tibbitts

I've been using a Tamron 17-50mm for about a year (lens was bought new) without incident on a K5, K5ii, and K200. The AF needed a substantial adjustment on both K5s, but otherwise there weren't any problems. On the day before a 2 week trip, I went to dust check the sensor, and, for the first time ever, the AF failed. Specifically, the lens seemed to intermittently disconnect electrically - it might rotate the barrel in one direction to focus, then the finder indicator would revert to MF, and then only intermittently switch back to AF if the lens was fairly forcibly rotated the tiny fraction of a mm that it could be rotated on the body while still mounted. Generally after mounting it would make one attempt to AF, then disconnect. The behavior was exactly identical on the K5 and K5ii. I tried the usual contact cleaning (with electrical contact cleaner), not that the contacts were apparently dirty, but it had no effect.

Throughout the 2 week trip (with the K5 and K5ii), through dozens of mountings/unmountings, AF behaved this way on both the K5 and K5ii. I tried AF periodically but no luck, which wasn't the worst thing ever, but mildly annoying. Exposure and all other functionality was good. Other AF lenses, Tamron brand included, worked fine with both bodies.

Upon returning, I tested the lens on the K200, and, just once, it behaved exactly as on the other two bodies. Then, after unmounting and remounting on the K200... it worked correctly. No wiggling of the mount had any effect. After repeated additonal unmount/mount cycles, it still worked. What's stranger, back on the other two bodies, same story... the AF is now working on all three bodies.

I'm wondering if anyone else has experienced similar behavior.

I own a Tamron 17-50, and while I've never experienced quite something like that with it (I'm having other issues with my own Tamron right now), I have had that behavior you are describing happen to one of my other lenses: a Pentax F 35-105 that I bought second hand. The AF basically just died a slow horrible death over a period of a couple of days. Since I was new to the whole photography thing at the time, I decided to try and fix the lens myself. Big mistake. All the little parts exploded into my carpet, I found what I could and shoved them all into a bag, and a year later I sold it all for parts.

However, it seems your Tamron has corrected itself, so hopefully your Tamron was just feeling under the weather for a while and nothing permanent has happened.

apfhex · 05-26-2014, 04:26 PM

Originally posted by tibbitts

I'm wondering if anyone else has experienced similar behavior.

Yes, pretty much exactly as you describe, once when I first got it. I took the lens off, wiped off the contacts, and it's been fine since. I think it probably is a poor mount connection of some sort.

tibbitts · 05-28-2014, 07:33 PM

Originally posted by apfhex

Yes, pretty much exactly as you describe, once when I first got it. I took the lens off, wiped off the contacts, and it's been fine since. I think it probably is a poor mount connection of some sort.

Thanks for letting me know your similar experience. I don't think there's anything I can do about it now, since I can no longer reproduce the error.

tibbitts · 02-26-2015, 09:09 PM

Not surprisingly, this problem returned after a few months. I returned the lens to Tamron, and it was returned promptly within the promised 3-day service window (hopefully Pentax is listening: three days!)

However the problem wasn't resolved. When I sent the lens in, I'd thought that wiggling the lens at the mount (there's only a tiny amount of normal play, same as Pentax lenses) would make/break the contact (and trigger the display of MF in the finder.) But now I've noticed that instead of seemingly being sensitive to the connection at the mount end of the lens, very slightly moving the focus ring (in AF - it won't move that far of course, not having a clutch) reliably returns AF functionality and turns off the MF indicator. But the problem occurs again almost immediately, of course - it seems to occur especially frequently after the focus motor drives the ring far to the left.

The lens is pretty easy to focus manually, and now that I've got a fairly quick workaround it's not so bad, although the obvious problem is not noticing the MF in the finder and therefore not noticing that the lens hasn't focused (if it's just slightly off.) I might send the lens back again with this new information - at least it's nice to have a long warranty that will let me do that if I choose.

**niceshot** · 03-03-2015, 04:47 AM

Hi Tibbitts you don't say why they didn't resolve it. Was it something they could not fix

tibbitts · 03-03-2015, 07:53 PM

Originally posted by niceshot

Hi Tibbitts you don't say why they didn't resolve it. Was it something they could not fix

It's intermittent, and always has been, so it's possible they couldn't reproduce it. I took a dozens of pictures with the lens last weekend and didn't experience the problem once. When the problem appears, it's persistent, even through lens changes, and occurs on multiple bodies. But then it goes away for a while.

tibbitts · 04-09-2016, 08:24 AM

I'm back to update this situation. As was the case three years ago, I'm again about to leave on a trip, and after a couple of years of perfect behavior, my 17-50 AF has again gone out to lunch. Same intermittent AF/MF switching issue - it's like it loses contact.

Here's new info: this is an important trip, and I really like the Tamron, so I bought another one from KEH. 100% identical behavior. The lens will usually make one attempt to focus, and at the end of the run (when the focus gets close, at least), will drop the body back to MF mode. In live view I can just move the camera slightly and the body will keep toggling into and out of AF. But on my bodies, the 70-300 LD Di, 10-20mm Sigma, and a whole bunch of screw-drive (and non-screw-drive) Pentax AF lenses work perfectly.

Oh and the KEH copy: also exactly a -10 (or maybe -11 if it was there) on microfocus.

The odds of this happening with my two different K5 AF mechanisms (K5 and K5ii) AND two different copies of the lens are... wow. I don't know what to do. MF on this lens isn't horrible, but I'd really like AF.

Incidentally KEH was good about taking the lens back, no hassles. They were as mystified as I am.

---------- Post added 04-09-2016 at 08:26 AM ----------

Originally posted by niceshot

Hi Tibbitts you don't say why they didn't resolve it. Was it something they could not fix

Sorry if I hadn't explained but Tamron returned the lens basically not identifying the problem, just saying they'd cleaned and adjusted it under warranty. I can't blame them, since for a couple of years now, I haven't experienced the problem either, and if it can't be reproduced, I can't expect them to fix it.

05-24-2014, 11:41 AM	#1
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,196	Tamron 17-50mm AF problem I've been using a Tamron 17-50mm for about a year (lens was bought new) without incident on a K5, K5ii, and K200. The AF needed a substantial adjustment on both K5s, but otherwise there weren't any problems. On the day before a 2 week trip, I went to dust check the sensor, and, for the first time ever, the AF failed. Specifically, the lens seemed to intermittently disconnect electrically - it might rotate the barrel in one direction to focus, then the finder indicator would revert to MF, and then only intermittently switch back to AF if the lens was fairly forcibly rotated the tiny fraction of a mm that it could be rotated on the body while still mounted. Generally after mounting it would make one attempt to AF, then disconnect. The behavior was exactly identical on the K5 and K5ii. I tried the usual contact cleaning (with electrical contact cleaner), not that the contacts were apparently dirty, but it had no effect. Throughout the 2 week trip (with the K5 and K5ii), through dozens of mountings/unmountings, AF behaved this way on both the K5 and K5ii. I tried AF periodically but no luck, which wasn't the worst thing ever, but mildly annoying. Exposure and all other functionality was good. Other AF lenses, Tamron brand included, worked fine with both bodies. Upon returning, I tested the lens on the K200, and, just once, it behaved exactly as on the other two bodies. Then, after unmounting and remounting on the K200... it worked correctly. No wiggling of the mount had any effect. After repeated additonal unmount/mount cycles, it still worked. What's stranger, back on the other two bodies, same story... the AF is now working on all three bodies. I'm wondering if anyone else has experienced similar behavior.

05-24-2014, 04:01 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	It could just be wear on the lens mount that caused looseness or just a poor electrical connection, hopefully it doesn't happen again! Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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05-24-2014, 04:44 PM	#3
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	I've not struck the same problem, but if it's the AF but nothing else, then it may be worth paying some attention to how the AF screw in the lens is mating with the body. There may be some movable grit or grime in the vicinity of the AF screw on the lens.

05-24-2014, 09:46 PM	#4
EarlVonTapia Veteran Member Join Date: Oct 2012 Location: Vancouver Photos: Gallery Posts: 1,207	Originally posted by tibbitts I've been using a Tamron 17-50mm for about a year (lens was bought new) without incident on a K5, K5ii, and K200. The AF needed a substantial adjustment on both K5s, but otherwise there weren't any problems. On the day before a 2 week trip, I went to dust check the sensor, and, for the first time ever, the AF failed. Specifically, the lens seemed to intermittently disconnect electrically - it might rotate the barrel in one direction to focus, then the finder indicator would revert to MF, and then only intermittently switch back to AF if the lens was fairly forcibly rotated the tiny fraction of a mm that it could be rotated on the body while still mounted. Generally after mounting it would make one attempt to AF, then disconnect. The behavior was exactly identical on the K5 and K5ii. I tried the usual contact cleaning (with electrical contact cleaner), not that the contacts were apparently dirty, but it had no effect. Throughout the 2 week trip (with the K5 and K5ii), through dozens of mountings/unmountings, AF behaved this way on both the K5 and K5ii. I tried AF periodically but no luck, which wasn't the worst thing ever, but mildly annoying. Exposure and all other functionality was good. Other AF lenses, Tamron brand included, worked fine with both bodies. Upon returning, I tested the lens on the K200, and, just once, it behaved exactly as on the other two bodies. Then, after unmounting and remounting on the K200... it worked correctly. No wiggling of the mount had any effect. After repeated additonal unmount/mount cycles, it still worked. What's stranger, back on the other two bodies, same story... the AF is now working on all three bodies. I'm wondering if anyone else has experienced similar behavior. I own a Tamron 17-50, and while I've never experienced quite something like that with it (I'm having other issues with my own Tamron right now), I have had that behavior you are describing happen to one of my other lenses: a Pentax F 35-105 that I bought second hand. The AF basically just died a slow horrible death over a period of a couple of days. Since I was new to the whole photography thing at the time, I decided to try and fix the lens myself. Big mistake. All the little parts exploded into my carpet, I found what I could and shoved them all into a bag, and a year later I sold it all for parts. However, it seems your Tamron has corrected itself, so hopefully your Tamron was just feeling under the weather for a while and nothing permanent has happened.

05-26-2014, 04:26 PM	#5
apfhex Senior Member Join Date: Feb 2013 Photos: Gallery Posts: 117	Originally posted by tibbitts I'm wondering if anyone else has experienced similar behavior. Yes, pretty much exactly as you describe, once when I first got it. I took the lens off, wiped off the contacts, and it's been fine since. I think it probably is a poor mount connection of some sort.

05-28-2014, 07:33 PM	#6
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,196 Original Poster	Originally posted by apfhex Yes, pretty much exactly as you describe, once when I first got it. I took the lens off, wiped off the contacts, and it's been fine since. I think it probably is a poor mount connection of some sort. Thanks for letting me know your similar experience. I don't think there's anything I can do about it now, since I can no longer reproduce the error.

02-26-2015, 09:09 PM	#7
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,196 Original Poster	Not surprisingly, this problem returned after a few months. I returned the lens to Tamron, and it was returned promptly within the promised 3-day service window (hopefully Pentax is listening: three days!) However the problem wasn't resolved. When I sent the lens in, I'd thought that wiggling the lens at the mount (there's only a tiny amount of normal play, same as Pentax lenses) would make/break the contact (and trigger the display of MF in the finder.) But now I've noticed that instead of seemingly being sensitive to the connection at the mount end of the lens, very slightly moving the focus ring (in AF - it won't move that far of course, not having a clutch) reliably returns AF functionality and turns off the MF indicator. But the problem occurs again almost immediately, of course - it seems to occur especially frequently after the focus motor drives the ring far to the left. The lens is pretty easy to focus manually, and now that I've got a fairly quick workaround it's not so bad, although the obvious problem is not noticing the MF in the finder and therefore not noticing that the lens hasn't focused (if it's just slightly off.) I might send the lens back again with this new information - at least it's nice to have a long warranty that will let me do that if I choose.

03-03-2015, 04:47 AM	#8
niceshot Site Supporter Join Date: Mar 2014 Location: NY Photos: Gallery Posts: 1,565	Hi Tibbitts you don't say why they didn't resolve it. Was it something they could not fix

03-03-2015, 07:53 PM	#9
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,196 Original Poster	Originally posted by niceshot Hi Tibbitts you don't say why they didn't resolve it. Was it something they could not fix It's intermittent, and always has been, so it's possible they couldn't reproduce it. I took a dozens of pictures with the lens last weekend and didn't experience the problem once. When the problem appears, it's persistent, even through lens changes, and occurs on multiple bodies. But then it goes away for a while.

04-09-2016, 08:24 AM	#10
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,196 Original Poster	I'm back to update this situation. As was the case three years ago, I'm again about to leave on a trip, and after a couple of years of perfect behavior, my 17-50 AF has again gone out to lunch. Same intermittent AF/MF switching issue - it's like it loses contact. Here's new info: this is an important trip, and I really like the Tamron, so I bought another one from KEH. 100% identical behavior. The lens will usually make one attempt to focus, and at the end of the run (when the focus gets close, at least), will drop the body back to MF mode. In live view I can just move the camera slightly and the body will keep toggling into and out of AF. But on my bodies, the 70-300 LD Di, 10-20mm Sigma, and a whole bunch of screw-drive (and non-screw-drive) Pentax AF lenses work perfectly. Oh and the KEH copy: also exactly a -10 (or maybe -11 if it was there) on microfocus. The odds of this happening with my two different K5 AF mechanisms (K5 and K5ii) AND two different copies of the lens are... wow. I don't know what to do. MF on this lens isn't horrible, but I'd really like AF. Incidentally KEH was good about taking the lens back, no hassles. They were as mystified as I am. ---------- Post added 04-09-2016 at 08:26 AM ---------- Originally posted by niceshot Hi Tibbitts you don't say why they didn't resolve it. Was it something they could not fix Sorry if I hadn't explained but Tamron returned the lens basically not identifying the problem, just saying they'd cleaned and adjusted it under warranty. I can't blame them, since for a couple of years now, I haven't experienced the problem either, and if it can't be reproduced, I can't expect them to fix it.