There is new firmware for the 645DF that corrects a minor issue with the Schneider Kreuznach 150mm LS. The issue is that if you set the camera body to half step aperture (1/3 steps are default) then sometimes it will jump the setting f/4, and go directly from f/3.5 to f/5.6. Users who do not own and do not plan to rent the 150mm LS can disregard this firmware update.
Download
www.phaseone.com/en/Downloads/Firmware/FirmwareUpdater.aspx