Nikon COOLPIX P7800 Reference Manual page 188

Using the Commander Mode
When the flash mode (A59) is set to z (commander mode), you can
wirelessly control an off-camera optional flash unit.
• Set the group and channel settings for the remote flash unit to "Group A"
and "3 CH," respectively.
• Place the flash unit within the range shown in the diagram below.
• Set up the remote flash unit facing the camera to ensure that the light from
the built-in flash will enter the wireless remote sensor window of the remote
flash unit. Set up the remote flash unit in a position closer to the subject
than the camera.
Approx. 5 m
(16 ft) or less
• The distances shown in the diagram above may vary depending on the
surrounding environment.
E60
50° or less
30° or less
30° or less
50° or less
Approx. 3.5 m
(11.5 ft) or less
Camera
(built-in flash)
Approx. 3.5 m
(11.5 ft) or less