Mamiya 645 PRO TL - Manual (Page 29)

Time Exposures Multiple Exposures
For time exposures set the Shutter
Release Selector to the self-timer
mode, and set the Shutter Speed
Dial to "B". Press the shutter release
and both mirror and shutter will stay
open until the shutter release is
pressed again. You may also use a
cable release together with the cable
release adapter. (The battery circuit
will automatically switch off to save
power.)
can be terminated by shift-
ing the Shutter Release Selector
from or the Shutter Speed Dial
from
Aligning the white dot of the Multiple
Exposure Lever with the yellow
“MULTI” square, disengages the mul-
tiple exposure prevention mecha-
nism, and the film will not advance
after an exposure is made and the
Film Advance Crank is turned.
However, the shutter will be recocked,
thus making multiple exposures
possible. In this mode the Exposure
Counter will not advance.