Thanks to everyone for your input - the point about the contacts and paint needs to be investigated further - one thing I can report is that I tried the 'a' 28mm with a tube attached, but not on the camera , just in my hand - now when I move the tube bayonet to one side then the lens aperture WILL adjust in accordance with the ring position - but with the tube bayonet moved to the other position then I lose the aperture control.

So it seems that when the tube is mounted on the camera that this bayonet is being moved into the position that holds the aperture wide open (this is for normal metering operations isn't it?) - something is stopping it from moving to the other position when mounted on the camera?? Is this to do with the contacts matter?

They have a black paint same as the tube body on the camera mount end - and a silver colour (like a standard lens metal mount) on the lens attaching end.

Actually, now you mention it, I have to say that on the Tamron (which does give me aperture control with the switch in Manual), the stop down metering is a bit inconsistent - sometimes it doesn't work well - I've had to judge the shutter speeds mentally after changing aperture sometimes.

But surely not all three in exactly the same way Andrew .. Could they all individually develop the same fault? Seems unlikely surely? The drinks vouchers can stay where they are, its worth it just for the learning and experimenting ... None of this would be anywhere near as much fun if I was actually able to take any photos with them!

Hi Andrew, to clarify those specific questions ... firsty about lens on camera only - with no tubes, and lens directly on camera, I have full control of the aperture with the lens aperture ring, plus I have correct stop-down metering (press green button in M mode, little pzziz noise, lens stops down and shutter speed is set) - all normal.

Now with the tubes on, any tube or combination of the 3 ... with the Tamron Adaptall auto-diaphram switch in 'manual', I have full control of aperture with the aperture ring, and I also have normal stop-down metering as described above.

Withe the tubes (any combination) and either the Pentax 'a' 28mm or 'm' 75-150 then the aperture ring on the lens has no effect - it does not change the brightness in the viewfinder, and there is no stop-down metering (no pzziz noise) - and the aperture remains fixed at full open. With the tubes and lens in my hand looking through, moving the aperture ring does not close the aperture in the lens - it remains fully open even at f22. Mystery?

But these lenses have an aperture ring, and are not set to 'A', so there's no electronics involved. I can turn the aperture rings but there's no effect when they are attached to these tubes. Removing the tubes and attaching the lens to the camera directly restores full control of the aperture from the lens aperture ring, including 'A' setting control from the camera e-dial in the case of the 'A' 28mm.

I don't understand why the bayonet lever on the lenses is being moved over and pulling the apertures wide open when attached to the tubes?

MORE HELP NEEDED PLEASE !!

Might as well ask this here, its a related issue. Having got sorted with my stuck Neewel tubes, I have also acquired a set of Jessops ones, which are more sophisticated with a proper mount and the bayonet lever ... the Neewel ones have none of this, they just attach really.

Unfortunately I have not been able to get the Jessops ones working properly. The problem is something to do with the 'auto-diaphragm' system, because I am not getting any aperture control at all - when my 'A' & 'M' series lenses are on the tubes the aperture remains fixed at full open. I see how this is happening with the metal lever (is that the 'bayonet'?) which when moved opens the lens fully. It seems that the lever on the tubes is moving this lens lever when the lens is fully mounted and therefore locking the aperture full open.

The shots I took recently (flowers) I had aperture control because this was using the Tamron Adaptall 135mm which has a 'manual / auto diaphragm' switch ... when switched to manual I have full control, but with the tubes and the switch at auto its the same as the Pentax lenses - stuck full open.

When the lens is not fully engaged onto the tubes there is some movement of the aperture, but not when fully locked in place. Its a mystery whats going on as these Jessop tubes seem to have all the required components for proper K mount operation. Any ideas and experiences would be much appreciated - I would much prefer to keep using the Jessops tubes as they are far higher quality and more solid than the other ore simpler ones.

Thats a lovely flower, and a very nice composition and pleasing colour. Its not looking critically sharp I have to say ... would that be because of the 'converter' - (is that a glass filter type?) -I have been looking into this lately and some advice suggests that 'close-up filters' can degrade IQ and sharpness a bit. Forgive me and correct me if you're set-up here is not in fact a filter.

Great advice, agree totally with all of that - they'll have to wrench the K7 from my hands when I finally .....

Another strong coastline set Tom! Favourite for me is No4 with its beautiful rocks and motion in the foreground, and it is all perfectly balanced I feel. No1 is so tranquil, really lovely with natural tones.

I do wonder if the sandy areas in 2 and 3 are just a tiny bit too bright, perhaps 1/3rd of a stop? And I'm not keen on the colours so much in the last flower one, not very nice green, and I don't find enough objects in the image to be in focus really.

Yes these are very cool and amazing! Best I think are 3 and 5, but they all have such vibrant colour and energy from the spinning which makes a winning combination. Did you need special permission to use the tripod? And do you mind me asking, with the big stopper, what sort of shutter speeds did you end up with to get the spinning ?