Mirror up operation is only recommended if using
Mamiya’s own double cable release.
The adaptor plate connects to the Mamiya body, and
the switch underneath is set to the L position (locked).
If you are using the Mamiya RZ Pro II adaptor you
should set the Shutter latency to ”Short latency”
It is possible to use Long latency on this camera, but
only when shooting using the capture button inside
the Capture One Application.