Just a few more notes on the original Pentax 645 lenses:
- the manual only (which you should look for for the 645) are the "A" versions
- the autofocus versions and usually more expensive, but working fine in manual mode on the 645 are the "FA" versions. If you think about using the 645n one day, nothing wrong in these already now. But the other way around, "A" on 645n is fine as well.
- ignore the "D-FA" and "DA" versions, they are meant for the digital 645D and 645Z. While they technically work, some (all?) have no manual aperture control, are more expensive, and the "DA" probably covers not the full film format.
- special case: "LS" lenses are leaf shutter lenses (75mm or 135mm), for higher shutter speed with flash then the camera's flash sync time.
And when I say "affordable" (of course for quality medium format lenses), here some examples of what I had payed, from Japanese auctions. All prices in Canadian Dollar, shipping and importation tax not included. All in great used condition.:
- (all manual A version): 75/2.8 & 150/3.5 & 200/4 & LS 135/4 & adapter to Fuji G-mount. All for CAD 640. I sold the Fuji adapter for CAD 140, so this makes CAD 500. Buying a single new full frame lens is often more expensive.
- (most FA lenses) FA 35/3.5 & FA 45-80/4.5 & FA 80-160/4.5 & teleconverter 2x & Pentax 67 lens 135 & adapter Pentax 67->645, all for CAD 395. Sold the Pentax 67 lens for CAD 140, the adapter for CAD 100, which makes it CAD 155. The 35mm alone sells often for 300-400$. Compare this to the listed price at B&H for the lenses (current rebates): The 45-85 for USD 2,400, the 80-160 for USD 1,900, the (newer D-version) 35mm for USD 1,600.
- the A 55/2.8 for CAD 155 (and a few more longer FA lenses, all below CAD 200)
I think I bought not bad, but I guess with a bit more waiting you can find them even cheaper.