Nikon D6 Reference Manual page 682

4
Adjust synchronized release settings.
Configure the master and remote cameras as described
below. Press 4 to return to the previous display when
settings are complete.
Option
[Group name]
[Master/remote]
630
Synchronized Release
Enter a group name for the synchronized
cameras. Group names can be up to 16
characters long.
•
The master and remote cameras must all be in
the same group.
Choose a role for each camera from "master" and
"remote".
•
[Master camera]: Pressing the shutter-release
button on the master camera releases the
shutters on the remote cameras. Each group
can have only one master.
•
[Remote camera]: The shutters on the remote
cameras are synchronized with the shutter on
the master camera.
Description