All shots apart from the one with the Pentax A 50mm were auto focus, the conformation beep was heard before the shot was fired, all shots were taken on a tripod using a wireless remote. Also apart from the 50mm with all shots the focus ring was moved to put the lens out of focus and the shutter button half pressed for AF to correct as required once the conformation beep heard the shots were taken with the remote. With the 50mm, as AF was selected it will not fire until the focus ring is turned and focus is achieved (catch in focus) again with a conformation beep.

Thanks Gary, I've now taken some shots and cropped to the focus point the final 3 using your advice.
Focus achieved by pressing the shutter half way except while using LV when the AF button was used.

1. 16-50 @ 50mm through viewfinder



2. 16-50 @ 50mm using Live View



3. SMC Pentax A 50mm f1.7 @ f2.5



4. 55-300 @ 55mm through viewfinder



5. 16-50 using 0 AF adjust



6. 16-50 using +5 AF adjust



7. 16-50 using +10 AF adjust



verdict ... still very poor for a £700 DA* lens!
Even adding +10 AF adjust it gets nowhere near as accurate a result as the 55-300
If anyone has any ideas on what to do I would be eternally grateful as I have a family function to photograph next weekend (no, not that one!)
and I want to be sure the photos are sharp and in focus.

The lens was pointed at the writing on the bottle, focus confirmation beep was heard and shot fired. So for a £700+ lens I kind of expect the picture to be sharp and in focus. As stated earlier it was repeated on a tripod with a wireless trigger and the same result (blurred and oof). The same shot was taken with a Pentax A 50mm and a DA 55-300 and both faired better...much better.

Am I right in reading that you have used the 16-50 under water!

Yes focus is set to centre

My DA*16-50 doesn't appear to be focusing at all, I have included a link to a photo taken this morning and would like your expert opinion on whether it's me or the ff/bf issue people have been talking about with their K-5s. The shot was taken on Program mode and the camera pointed at the writing on the side of a pop bottle. The camera automatically opted for f2.8 and a shutter speed of 1/40, center focusing but on close inspection nothing is in focus. I admit there may be a little camera shake but this is OOF blur not CS blur, also there is an alarming amount of CA at 2.8. I have repeated the test on a tripod with the same result, with Live View it is marginally better but considering the price of the lens I would expect it to be perfect. Is there anything I can do to put it right?

Lovely set of (alternate name) May Bugs they have an awesome set of antennae. Well taken.

Brilliant

I previously had a bridge camera a Fuji S100fs, this had a crosshair in the viewfinder and whatever that crosshair was on was focussed even in very busy areas, also in the dark it had a very green light that was used to illuminate the subject and it focussed brilliantly even in total darkness... are you watching Pentax?

Took a walk with the wife around Bonvilston here's a few pics from the day. Most where taken with the old 50mm, it is almost permanently attached to the K-7 lately with or without tubes.

1. Crane flies making the next generation



2. Fungi



3. Fields of gold



4. Butterfly (no tubes used just stealth)



5. Pretty pink flower



6. Odd coloured bee/fly



7. Buzzard getting mobbed



8 And of course the obligatory spider shot