Out with the camera this afternoon, the AF stopped on my 50-135 as I took the last shot on a windy ridge. I went through all the usual checks and walked back to the car thinking the worst. It is one of the very early copies of this lens, owned from new and has had a good deal of use and abuse as my most often used lens, so I considered the SDM had done well on balance; I mean every SDM fails sooner or later yes? Well I got it home and had another play and it seems I had knocked the lens into manual - I only checked the camera AF selector and forgot about the switch on the lens - idiot ! I was all ready to enable it's screw drive.

Anyways, the weedy SDM in this chunky 2007 lens is still going strong. I guess some of the old ones just keep going. I'm very happy, but that's only because I believe I am on borrowed time wiith my SDM...

Let's hear it for the SDM's that keep working.

Thanks for all the feedback. One more question if I may. Is the zoom ring action like that of the 50-135, which has very little resistance and can be thrown quickly and easily from one extreme to the other without destabilising the camera? Very few lenses have this advantage; in fact, I can't think of another that's comparable . Because the 16-50 extends, unlike the 50-135, I'm guessing it will have a good deal more resistance to turning. There's no dealers with this lens close by unfortunately.

Mmm, I might get a quote for the calibration of mine - you are not the only one to talk of major improvements from that course of action. It's good to know your 16-50 is a happy match with your K3. In what respect did it improve after calibration?

Thanks for your response Blythman. I really enjoyed browsing your images.

I have the 50-135 which is wonderful (7 years with it and no SDM issues). Can anyone who has both lenses tell me if the 16-50, despite all its known issues, has some of the 'bite' and generally fab IQ of the 50-135. I've read many reviews and users accounts, but I'm still not clear about this. Are their respective IQ's discernibly related by their DA* lineage, or is the 16-50 just another WA zoom that would in practice be near impossible to differentiate from my 16-45. In particular, is it sharp at infinity and useable for landscape work. I can bear a bit of softness in the corners if it is distributed evenly amongst all four of them.

I am beginning to think the 50-135 has spoilt me and that I will struggle to find a good partner for it unless I buy primes. That said, my 35 macro is unreliable at infinity despite AF tuning to my K5 and I'm forced to manually focus it for landscapes most of the time (no bad thing really). However, this still yields results that don't stand up to my 50-135 in terms of sharpness. My 12-24 is good in the centre, but is a bit de-centred and not at all impressive at the long end. My 16-45 has the same de-centred problem it seems with the right hand side suffering quite noticeably (checked on three bodies). Unsurprisingly, I'm low on confidence with Pentax sub-50mm glass at the moment.

Ordered mine from the supplied Jessops link on Thursday (thanks jeallen01). No seal on box, Shutter count 8, battery charged and installed, serial 497xxxx, build 03/2014, V1.00, no signs of menu use, electronic level seems fine, chassis warmer to the touch than my K5 (thicker plastic coat?) and 20g heavier. No complaints, but yet to test it thoroughly.

The last Pentax DSLR with a CCD was the K-m surely? The 'mini' was dismissed by most on this forum and is not destined to be a classic, but I won't be getting rid of mine based on its output. No focus point, but it always seems to know where the subject is..

Lens received. Thank you Russ.

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