I was a bit shocked this afternoon when I took my Tamron 17-50 out of the bag to put it on the camera and found the front of the lens was wobbling - i.e. loose. On closer examination it appears to be a ring around the front of the lens which holds the filter thread and lens hood thread, but is other wise separate from the lens assembly, i.e. it doesn't seem to affect the front element.

In some ways I'm not surprised as fiddling with filters over the years I have often been concerned that I was putting undue pressure on the front of the lens, and more recently the lens hood has been very stiff to take off (I store it reversed on the lens). This is also by far my most used lens over the last 5 years and so I guess if anything was going to wear out then it would be on this lens.

I thought this might not have any impact as the lens elements were not affected. However it does seem to alter the edges of the frame with filters mounted. There are no obvious screws to tighten or method to disassemble this filter assembly. I checked my Tamron 11-18 and this has the same sort of lens front assembly, although there is no play on that lens; it is nice and tight.

Anybody any experience with this sort of issue?

I know that situation. So:
There's a plastic ring screwed like a filter (just there where you screw on a filter, down to the end).
Take a small piece of rubber, gently squeeze on that plastic rim (don't worry, you wont damage the front lens) and enable it to unscrew from its place, as if you were taking out a filter. You might use 2 rubber pieces and do the same from 2 opposite points.
Once its loose it will easily screw off.
Take it out and you'll see some screws underneath which are there to firmly hold the front part of the lens. You'll see they are loose, it's even quite possible that 1 or 2 would be out of their holes.
Just firmly screw them and mount (screw on) that plastic rim in its place firmly with the rubber(s) mentioned above.
BTW, you might even consider for a rubber a small part of the inner camera of a bicycle tire.
Good luck.

Thanks for the advice Doc. I will investigate.

Yep, I had the same issue and fixed it as suggested.

I had a second issue when the lens fell out of my pocket - the zoom ring became stuck, a bit of effort freed it up, but now it is out of position with respect to the focal length markings. At least it still works (but in the exif it only reports a zoom up to 30mm, so I guess the anti-shake could be a bit off).

Birma I couldn’t find any repair manuals or exploded views for part numbers etc. so far on the 17-50/2.8 but I did find a discussion fairly similar to what Doc was saying, there was a guy with the same problem on the same lens in the second last paragraph/post, so it sounds like an issue with that model lens maybe, the op had a different model (28-75/2.8 ) but similar problem, supposedly, and he fixed it himself, he said Tamron were a little excessive with their repair charges quote and I tend too agree. http://www.fredmiranda.com/forum/topic/661823 (there could be his version of fixed and the Tamron version of fixed as well, and they might not necessarily be the same)
I don’t know how one damages the hood bayonet area on the 28-75, I had a look at mine (it’s a KM but the design should be the same, one would think) and it looked pretty solid too me, I guess if one actually drops the lens onto the hard floor or such, that could do damage of some sort.
Greg

Thanks Anthony and Greg for your help as well.

I have investigated and discovered that on my lens the piece that I need to take off to expose the screws 'pops' off rather than screws off. There is a small gap to enable you to prize it off with a tiny screw-driver. This exposed three screws. I tightened two, which imporved the 'wobble' a great deal, but the third screw was jammed. I suspect what ever impact or force caused the damage has damaged this screw in-situ and it is now stuck. I can live with the remaining wobble, so not a right-off. I will start storing the lens hood loose from now on .

Anthony - I have had the problem you describe as well. The zoom grip has slipped its gearing. I managed to get mine back in the right spot through applying quite a stiff, controlled twist. I advise extreme caution however as this could have been terminal if it had gone wrong .

Obviously, I now have a GAS attack - what wide to normal tele zoom should I be after as a replacement? My first instinct when I noticed the wobble was a rather perverse "whoopie - now I can get the CZ 16-80", rather than "oh no - my lens is damaged". I believe there is also a G zoom lens expected for the Nex? Something else to think about.

Thread lock is your friend! I've heard of this but didn't notice it with my lens when I had it. But I didn't have it that long so I probably wouldn't have anyway

Sorry to hear of your lens troubles. One obvious lens to consider as a replacement for your Tamron 17-50mm f2.8 is the Sony 16-50mm f2.8. Bigger and heavier though, I think.

My copy wobbles in the exact same way, only there seems to be some kind of interior damage, also. I can see a distinctly formed ring on one of the elements, concentric with the axis of the lens, appearing to have been worn into the coating (or deposited there) by some repeated mechanical means. I really ought to send it in to Tamron, but I don't know how much to expect of them.

I was having a good look inside my lens while fiddling with it, but don't remember anything like this. I will have to check again.

Thanks Henry, and DK has just posted a review of the same - very handy

Strictly speaking, the optically best of all fast zooms is the Sigma EX 17-50 OS HSM. It's focus plane is as flat as that of a regular macro lens, and it's also very sharp all across the frame.

But the Sony 16-50 gives you all-time DMF, weather sealing and auto CA and geometry corrections with a77...

Open to debate on this one. The Tamron does better on the edges at faster apertures. I was happy to shoot at f2.8 at "ALL" focal lengths. The Sigma is a nice enough lens but on bang per buck the Tamron kicks it out of the park and then some.

I should have mentioned the Tamron alongside the Sigma at the end of the article, I'll add that.

David