Digitally-designed lenses have a telecentric design. This means that light rays are parallel when they exit the rear element. The light thus falls squarely into the pits on the sensor surface that hold the individual pixels.

Some film designed lenses will work very well, especially from short telephoto onwards. Some won't, especially the wider angles.

The Pentax experience is already there and indicated very well by their approach to the 645D. By and large the existing 645 lenses have been kept, but the wide angle and macro have received new updated designs. I would expect that any "FF" Pentax system would do the same. Pentax are not going to release a system camera without any lenses to use with it.

There's nothing to fear about this and I will just wait and see what actually happens before making any decisions. The only thing I can say at the moment is that I am very unlikely to want to move to a FF system of any kind.

PS This all presumes that the sensor used in a Pentax FF camera still had pits in its surface. It's always possible that new sensor designs could render telecentric design requirements as obsolete.

I missed answering the question about the lens I used in my picture: it was the 18-135mm WR

It does Deryn, although I find it a little on the harsh side.

The Yashica 60mm Macro looks very nice indeed.

Very nice blue Algi!

Tamron and Sigma won't be cheap either, no macro lens is.

How about the idea of close up lenses or maybe extension tubes? That will be less expensive.

The lenses are excellent and if it's all in top condition it might well be worth £100. Why not make an offer? You can sell what you don't want on eBay and recoup your outlay plus perhaps more.

Geordie01 has it in a nutshell.

With Adapter K even a screw thread SMC or Super Takumar 50mm f/4 would do very nicely.

Most manual focus ones go to 1:2, but the addition of an extension tube will take them to 1:1 with no problem.

1:1 is extremely close - it seems very close for food?

For pictures of food, why not try the humble close-up lens first? Stopped down to f/11 or f/16 it should give excellent results.

In terms of focal length a 50mm Macro, if needed, might be better. Normally I would opt for a 100mm Macro but sometimes that does leave us too far away. Why not a Pentax macro lens? Even a second hand manual focus one could be ideal for what you intend it for.