jump to medium format

[cdd29]

Hi. I'm considering moving to digital medium format. I do a lot of night, landscape and some astrophotography. Not much portrait work, at least for now. My work in the past has been 35 mm film and either crop sensor or recently full frame digital. For now, I'm considering a Pentax 645D. One question I have is would all older Pentax 645 lenses be backwards compatible or would they require an adapter?

[MattBurt]

They are all compatible. You might also like 67 lenses which do require an adapter.
The 645D's sensor is a little smaller than 120 film so there is a ~1.3 crop factor (IIRC).