Nikon D850 Menu Manual page 239

4
f: Group the remote flash units.
Choose a group (A–F) for each of the remote flash units. The
master flash can control up to 18 flash units in any
combination.
5
C/f: Compose the shot.
Compose the shot and arrange the flash units. See the
documentation provided with the flash units for more
information. After arranging the units, press the i button in
the flash info display (0 243) and select M Test flash to test
fire the units and confirm that they are functioning normally.
6
C: Frame the photograph, focus, and shoot.
Optional Flash Units
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