An M lens set wider than f22, say f8, can only stop down to what it is set to, in that case f8. M lenses do not have electrical contacts so cleaning the mount contacts on the body will make no difference, just set the aperture and the camera will work out the shutter speed (and should show you the shutter speed in the viewfinder, just like using the lenses on an M series camera.) With the DSLRs now you have to press the green button to take a reading, but not so with that.
With the A lens, you can either set the aperture on the lens and it will work like your M lens, or put it on the A setting (just beyond f22) and you can set the aperture from the camera body as you would with a current DSLR (it'll use those contacts to communicate.)

The only lens I nearly boo-boo'd on trying them out was an old K/R mount telephoto. Just stopped in time! Not had any problems with lenses not fitting otherwise. I suppose even that K/R one would have fitted... but possibly permanently!

I've not noticed any issues with mine either. Seems to work quite well with the K-1.

I don't agree with that though! If you want dedicated video one buy a video camera! If video can be incorporated without impinging on the still camera aspects then fine, at least video is incorporated to some extent for those that have the occasional need. If one's main need is for video then it might be the wrong camera for them (though not necessarily even as it is.)
I never expected my Pentax ME to produce super 8 movies, and vice versa. If you want steady video, buy a tripod, or perhaps dedicated video lenses could be produced with inbuilt stabilisation, I do believe that technology exists?

I agree with that too.

I didn't particularly want to install PDCU again as it performed so badly on my PC last time. It was frustratingly slow. Once bitten, twice shy. (Must have been written in 8 bit basic!) What's more my SSD is practically full and I think Windows needs much of the spare capacity left (only 7Gb remaining) so I'd need to uninstall something else first! I've already ditched Adobe reader, that gained more than I expected! And I tried those Nik plug-ins and they've gone already too. Anything installed has to be something essential now.

I've just converted my pixel-shift test image using Adobe's latest DNG converter (v.9.5.1.)
This is a 100% crop (actual pixel crop)




So it is clearly each image merged but no other processing done on it - seems ACR doesn't do it.

This is the in camera jpeg version at actual pixel crop.



and this is how the older Adobe Camera Raw 7.3 handled the dng file




Not sure what to make of them all!

In case you're wondering, this was from near the edge of the frame and wasn't the point of focus but it does show how the image was processed.

Clearly, any use of pixel-shift requires the use of a very rigid tripod, not hand holding as i've seen suggested elsewhere. And any failed images can be rescued in ACW 7.3 which looks better than the camera's own jpeg version.

If one only got one of the four images that make up the raw file surely it would be either all red, all green or all blue. But it isn't. The camera processes the data and combines it to produce the jpeg so presumably the raw file is combined too. (Presumed being the operative word!) Maybe PDCU can separate the layers back out. I'm in no rush to install it to find out given its previous sluggish performance that led me to uninstall it last time.

Perhaps someone with a K-3ii has experience of how to process it?

I'm not completely sure on this, but the raw file image I tried in pixel shift mode loaded OK into Elements 11, the only oddity was the file size of the dng was massive, 160mb compared to a normal one's 40mb. So it seems the camera does any necessary processing (it takes a moment or two to combine the four images) and presumably the camera jpeg is ready processed. So one can see right away if its worked OK or if need to try again. It seems much the same system as the in camera's HDR process, you don't need any dedicated software for that.
What I will say is that the out of camera jpegs from the K-1 are the best I've seen so far, seems post processing makes them worse!

I also have an A 35-70. I've not really used it much but will take something tomorrow. The reason I haven't used it is that I also have a Chinon 35-70 and that has always amazed me with its sharpness. i'll do some comparison shots tomorrow (well, later this morning when I get up!!). Melness, is it for use on Full Frame or APS-C? I'll take the samples accordingly.