Mamiya RB67 Pro SD User Manual page 33

Using the Mirror Lock-up Cable Release
1. When exposure is shorter than 1 second:
(1) Screw the short cable into the mirror lock-up
socket, and screw the long cable into the
shutter release button.
(2) By pressing the cocking lever forward as
far as it will go,cock the shutter and the mirror.
(3) The first stroke will make the mirror rise,
and the second will release the set speed.
*For lenses which use the mirror lock-up
operating knob, align the knob with the
MIRROR LOCK-UP indicator, screw in
the short cable, and screw the long cable
into the shutter button. The first stroke
will make the mirror rise, and the second
will release the set speed.
2. When exposure is longer than 1 second,
it is convenient to integrate with time(T):
(1) Screw the short mirror release cable into
the bulb unit of the lens, and screw the long
cable into the mirror lock-up socket.
(2) Set the shutter speed ring to T.
(3) Raise the mirror by pressing the shutter
release button on the body.
(4) The first stroke of the mirror release will
open the shutter and the second stroke of the
mirror release will close it.