Thanks for these comments, guys. The lens was bought in Thailand - I have an international warranty, but the returning it to the dealers there is no easier than sending it for servicing in the UK. I suspect it might be an issue with the motor - that would certainly make sense.

I like the idea of buying a K20D to solve the problem...but then, as I won't be back in the UK until July, perhaps the K-7 might be a better option??!

Hi,

I've been lurking on this forum for some time and gaining lots of insights from everyone's comments, but thought I'd post now to see if anyone can help me specifically...

I have a DA* 50-135mm which I have been trying to use on my K10D. It started out with no problems, with the SDM focusing working fine (my firmware is up to date), but then it stopped working. Now it sort of stutters rather than locking into focus, meaning that I've been using the lens with manual focusing. When I took it to the Pentax Service Centre here in Beijing, it worked fine on their K20D...of course they didn't speak any English and my Chinese is pretty weak too and so I couldn't point out that I'd tried it on other K10D bodies and it wasn't working then either.

I'm pretty sure there's a problem with the lens, but I know the K10D can have issues with the AF. I'm coming back to the UK in a few weeks (about 4 days before the warranty on the lens runs out!) and am planning to send it off for servicing, but want to check whether anyone else has had a similar issue with this lens on a K10D body.

Any advice would be great!

Thanks,

corin