p131, under focusing, in the memo section.

But the wording doesn't make what actually happens all that obvious.

Don't saw it off the lens, silly - machine the mount down by 8mm. That'll bring the whole lens closer to the sensor, and you'll still be able to attach filters, or indeed a teleconverter for a very handy 20-94.

Thank heavens she was on the way up...

You seem to be considerably more expert at sarcasm, than you are about understanding testing techniques.

Maybe your photographic technique really is so unusually expert, that you can discern the quality of a lens when you're taking hand-held photos of dark, moving subjects, with slow shutter speeds. Maybe you really are that excellent at holding a camera steady, and picking the 1/15s when the subject isn't moving at all.

And maybe you aren't, I can't say.

What I can say is that if you return your lens to Pentax, you might need some evidence that they believe as well.

And unless you exclude all the obvious things like shake, subject movement and depth of field, using sensible test conditions, you might find that they don't believe you.

You may be completely right about your lens. I'm not ruling it out, and I'm in no way blind to the possibilities of equipment problems. Indeed I was one of the first ones here to point out (in the face of some opposition, I might add) the K10D's metering issues with old lenses.

All I'm saying is that the conditions in which you took the pictures you cite as evidence for your claim are very bad test conditions which will prove nothing to an outside observer.

Getting some good shots with one lens at slow shutter speed, and then some bad shots with another, also at slow shutter speed, proves nothing, because other causes of variability have not been excluded.

Like it or not, the least consistent bit of equipment used in picture taking is the person pressing the button.

It's very easy to put a camera on a tripod and exclude camera shake and test for back-focus.

Rubbishing a lens simply on the basis of a few shots taken hand-held in the dark seems premature to me. Sure, if you're suddenly getting worse results than you're used to, it warrants some more in-depth testing, but unless you do the testing, you can't possibly make a meaningful judgement.

It is functionally, and as far as anyone seems to be able to tell, electronically identical to the Pentax AF540-FGZ, which is the most powerful and newest flash from Pentax that is compatible with the K10D.

The only apparent difference is that it says "Samsung" on the front, instead of "Pentax".

The Pentax badge isn't worth approx £120 to me, on a flash gun at least, so I got the Samsung, and it's been fine.

Depending on how 'ish' you are in reality, rather than in your hopes, the Samsung equivalent of the Pentax AF540-FGZ is periodically on sale at Amazon for £181 delivered.

It's the SEF-54PZF, and well worth waiting for, at that price, IMHO.

I think it's going to have to go on my wish list then.

Once I realised (talk about a flash of the bleedin' obvious :roll that for AF purposes, the camera 'sees' at the lens' widest aperture, the 16-50's potential utility in low light became a lot clearer.

It's not often that I'd want F2.8 for landscapes, but for seeing in the dark I definitely would.

Ok, supplementary question.

How much better?

Is it going to be along the lines of "much, much better; will substantially improve hit rate in bad light", or more like "a bit better, still quite hit and miss"?

I realise this is a bit harder to answer meaningfully, but I'd appreciate any attempts.

The context for all this is my attempts last night to take pictures at a dance venue, where the light was low, people were moving about quite a bit, and there were bright flashing coloured lights about.

AF aside, I was quite impressed with the ability of the AF540 (Samsung version) to expose decently. I was using it off-camera, all auto, mostly bounced with pop-up. Given that quite a few of the couples were wearing predominantly black or white, they wasn't the easiest of subjects.

Optical qualities and AF quietness and speed aside, would you expect the ability of the K10D to get AF lock in poor light to be better with the 16-50, purely because of its wide-open aperture being F2.8 rather than that of the much slower 18-55?