Mamiya RZ lenses (factor) and ZD back

[Graham Welland]

Sweet spot ...

[John Camp]

I have a pretty complete set of Mamiya RZ lenses which I haven't used for a while. If I buy a Mamiya RZ IID, and stick a ZD back on it, how will the lenses interact with the sensor? Since the ZD is essentially a 645 sensor, will you wind up with a lens factor like the Nikons in 35mm, where you gain on the long end and lose on the short? Or won't this have an effect? If the ZD will work as a fully functional RZ back, this is gonna bring a lot of RZ equipment out of the closet. The lenses are extremely sharp, and if they're going to work theway I think they will,we'll be using only the sweetest spot of amazing lenses...

JC

[BJL]

There will be considerable "sensor cropping" of between 1.44x and 1.56x depending on whether you compare the short of long edges of the differently shaped frames: the ZD sensor is 48x36mm (4:3) while the 6x7 film frame is about 70x56mm (5:4). So you lose about as much wide angle coverage as with 35mm format lenses used on the smaller format DSLRs from Canon, Nikon etc.

My guess is that sensors could move up to about the full 645 format of 42x56mm, giving about a 1.33x factor, but probably not beyond. The industry wide concentration on moving to and modernizing 645 format combined with the lack of efforts to update the larger roll film formats (no sign of auto-focus etc.) suggests that "medium format" is consolidating on 645 format for its digital future.