Sent a pm but if a group meet can be arranged then I would like to come. Like davidwozhere I am pretty busy but life takes priority sometimes!

Erm, my comments are about the new lens so apologies to theonenadeem if that's not the one he is interested in. Maybe we should split this into two discussions?
.

To my eyes only John's first photo looks very sharp, this is the only one I have which I am happy with in terms of sharpness. The more distant the subject, the less good it gets.

I am struggling to get really sharp photos with this lens on landscape and general views but managed a couple of acceptable ones at close-up so it's probably me. Nice blurred background though. One of the comments was that it's ok for a 'cheap' lens - at £529.00 I don't think so! I opted for this as a general walk-around lens on the K-1 in preference to the much heavier 24-70mm and I do find the combination very manageable.

If you mean Outdoor Photography then I am a subscriber, it is not equipment or technique obsessed but just publishes stunning images from amateurs and professionals alike with some great journalism.

PS. So here is a simple test to check whether a lens mount is ok - take a standard Pentax rear lens cap and see if it covers the mount; if not, then be careful.

I am sure the issue is with Sigma's mount construction. Here is a side by side comparison with Sigma on left:


To emphasise the difference in mount diameter here's one with a Pentax cap which completely covers a Pentax lens mount, but leaves a Sigma mount exposed by a wide margin:


The outer part of the Sigma mount with the four screws is raised by a very small amount, and as the screws are countersunk marginally below the surface of this ridge you can just feel the edges of the holes. I reckon these are the cause of the problem.

Well I will be swapping my Sigma for a Pentax lens as soon as funds permit.

Correction - having seen the photo in the link above, yes there is a very faint scratch just above the lens mount of my K-1 from the Sigma 150-500. Not as noticeable as in the photo and cannot be seen with a lens in place. So, Sigma will modify their lenses but who is going to rectify the damaged bodies? I guess Pentax will say they aren't responsible for what third party products do and maybe Sigma weren't given a pre-production model to test, so it's down to goodwill by someone.

Comparing a Pentax lens mount with the Sigma, the Sigma has a much wider plate with countersunk screws near the outer rim. If you run a finger over these you can feel a sharp edge to the hole the screws are set in which is presumably what is causing the problem. So I would say the fault is definitely with Sigma's mount.

Yes because it is still better than the alternatives and the lenses will be fixed. I have used the Sigma 150-500 which didn't scratch the body and got really sharp results, and compared to my K50 any noise at high ISO or poor light can much more easily be removed in Lightroom without noticeable loss of sharpness.