Consider it done.

The Pentax is a perfectly good lens, but without electronic contacts.

The Chinon and makinon are £10 on eBay fodder...

I would have liked Julia Margaret Cameron, but in her absence chose someone else.

I have never seen any difference between the sharpness of my images focused by any type of light. I routinely do studio portraits which although lit by flash are focused under tungsten or fluorescent lights. It doesn't seem to be a problem.

The K10D has a slight tendency to yellow, probably intrinsic to the design. The IistD is warm neutral and the K7 neutral.

Of course you could change this with all the cameras.

The pictures look much better than the first set!

Now the whites are under control, without clipping. Excellent. The K10D seems to have a slight colour drift towards yellow. Another variable here if you're using AWB. Set everything to daylight and there should be less variation. All sRGB now?

The results are very close, but I prefer the colour rendidtion of the *istD and K7.

As for the metering there are two possible explanations. One is that Pentax have changed the K value of the metering - the value that defines mid grey. The other is that the readout only gives fixed values that are approximate, even though the camera can deliver any intermediate speed. A slight variation could send the readout value one way or the other. As long as the exposure is OK I wouldn't worry.

Spot on.

That may help. I have centre weighted metering set on all my digital cameras and find that exposures are less prone to over-exposure as a result.

If you resize to 800 pixels wide before uploading to Photobucket the forum will handle the images better.

In any event, there's a bit of a problem with clipping of the yellow tones, meaning that detail in the brightest part is being lost. A slight reduction in exposure will help.

It's interesting that you say two of the images are AdobeRGB, because for the web somewhere they are being changed to sRGB anyway. Whichever colour space you choose, it's essential that the camera and Photoshop are set to the same. You will also get better results with web display if you make your images sRGB.

Did you not get a warning dialog from Photoshop about colour spaces when you opened the files?

Hope that helps!

Sometimes it doesn't take much if you're unlucky as to where the impact occurs.

First thoughts are how old is the lens? Guarantee? Household All Risks insurance?

At least get a quote from someone, after all it's a superb lens and maybe it can be fixed easily. It needs a technician to examine it, not a shop person to make wild guesses.