Pentax 645 lens to Pentax 35mm body

How well does the adapter ring work on the more modern slr bodies? I have a bunch of manual focus 645 lenses that I'd like to use if it's worth doing.

Ok. I'll come clean. I bought a Pentax istDL digital slr for the business and I'd like to save some company money by not having to buy a new set of lenses for this camera. That's what I want to use these lenses on. I still only use film for my artwork. B&H says this about the lens mounting of this body.

"PENTAX KAF mount compatible with PENTAX KAF2, KAF and KA mount lenses
Power zoom function not available
K-mount lenses usable with restrictions
S-mount lenses usable with adapter and restrictions
67/645 lenses usable with adapter and restrictions"

What are the restrictions? I don't care if I have to use the camera manually just as long as it meters internally and runs the aperture blades when I shoot. Will the adapter ring allow me to get a ttl meter reading and run the blades?

Any help will be greatly apreciated. If a moderator kills this thread because I used the "D" word, I'll understand.

From an identical thread on "ThePhotoForum" :

I have a DS and also used to use a manual focus 1.7 50mm lens on it. I imagine it's probably the same as using a medium format lens w/ the adapter. It does not provide any metering for you at all, so you're pretty much on your own. There's some trial and error involved, but you should have a good idea as to the correct aperture/shutter speed to expose close to correct if you used medium format cams before.

Click to expand...

If you use the Pentax K adapter, your lens' focal length will operate as the 35mm lens of the same numerical focal length (eg. Your 75mm standard lens for the 645 will be the equivalent of a 75mm lens on the 35mm camera body). Makes things awfully simple, doesn't it? Also means your "super-wide" 645 35mm lens is just a wide "normal" for 35mm work. This same holds true when using a 67 lens on a 645 using the 645 adapter.