Alexander6x6
Member
Then it seems the best medium format lenses to adapt to a different system are the Pentax lenses. I don't know the 645, but the 67 has a slide on all the lenses to stop down and it will stay in either position.
Hasselblad lenses as well. But if you are looking for the top performers on the digital sensor, then the Mamiya RZ67 or K/L together with the latest generation of Hasselblad Carl Zeiss lenses is the best option.