Originally posted by funkythiru Shouldn't true MF be 6x4.5? Is it possible Pentax is working on that?
The 645z and D are the equivalent of cropped frame versions of 645 film size.
The new sony sensors are close to the original 645 film format. As far as lenses are concerned, if you buy the film lenses (or the non-cropped lenses), you are good to go on the full frame sensors. Except of course of they switch to mirrorrless and change the distance between lens mount and sensor. Will have to wait and see.
Apologies to those that think this is off topic. Just hard to resist being passionate about my addiction :-)
There are other threads on the forum with detailed information about the lenses and sensor format dimensions, etc. etc.