[Scot628]

Hi all
Hopefully someone can advise me if I'm making an obvious mistake or whether I have a problem. I bought a Tamron 17-50 f2.8 new from Amazon (uk). The problem is that it often but intermittently resets itself to manual focus, regardless of what the setting on the K5 body says it should be. It doesn't do it every time, and sometimes if you give the lens a gentle twist it goes back to AF.S, but then back it goes to MF. I've tried my 18-55 kit lens and the FA35mm and they don't do it. So....is this just a lens with a bad connection that should go back, or is there an easy solution? Help!

[VoiceOfReason]

Clean the contacts and see if that works.

[Scot628]

Clean the contacts and see if that works.

Hi, I did try that (lens and camera) - it didn't help.

[felixkh]

Send it back for a replacement

[VoiceOfReason]

If it is seated correctly and you have no issues with other lenses then I would send it in for repair.

[Scot628]

Thanks, it's heading back to Amazon!

[LittleRestraint]

I've just had the exact same problem with a brand new 17-50 I've had delivered as well.

There's a faint click sometimes and it switches to MF in the viewfinder display, then the lens won't auto focus at all. I have to switch the AF on the K-5 body to MF, then back to AF to get it working again.

I'm pretty sure it's the AF screw drive connector not seating in the lens properly, almost like the lens is slightly out of tolerance. My K-5 is only a couple of weeks old, and all other lenses work fine.

Seems there may be a bad batch of 17-50 lenses. I'll be interested to see whether anybody else has an issue.

Shame really as it was my first foray into 3rd party lenses for my K-5. I so nearly bought the Pentax 17-70.

OP, did you get yours changed like for like, or did you opt for something else?

:LR

[krp]

I just discovered I have the same issue. I guess I'm glad to find out it's not the K-5 that's the problem. The only other AF lens I have is the Pentax DA-L 55-300mm and that works fine. But it's odd since my Tamron 17-50mm f2.8 didn't have this problem with my K-x.

[LittleRestraint]

Yeah, I've heard that they often work on the older bodies, like the K20D etc. I can only assume that the tolerances are slightly tighter on the screw drive mech with the K-5 or something, meaning it just doesn't quite engage properly. It's an odd one.

[Scot628]

I've just had the exact same problem with a brand new 17-50 I've had delivered as well.

There's a faint click sometimes and it switches to MF in the viewfinder display, then the lens won't auto focus at all. I have to switch the AF on the K-5 body to MF, then back to AF to get it working again.

I'm pretty sure it's the AF screw drive connector not seating in the lens properly, almost like the lens is slightly out of tolerance. My K-5 is only a couple of weeks old, and all other lenses work fine.

Seems there may be a bad batch of 17-50 lenses. I'll be interested to see whether anybody else has an issue.

Shame really as it was my first foray into 3rd party lenses for my K-5. I so nearly bought the Pentax 17-70.

OP, did you get yours changed like for like, or did you opt for something else?

:LR

LR - I sent it back and got a refund from Amazon. I was originally going to get a replacement, but ended up going for a Tamron 28-75 instead, which has been faultless. Shame, because the pictures from the 17-50 were great.