Nikon Z 6II Reference Manual page 697

D
Optical AWL
•
Position the sensor windows on the remote flash units to pick up the
light from the master flash. Particular care is required if the master flash
is mounted on a hand-held camera.
•
Be sure that direct light or strong reflections from the remote flash units
do not enter the camera lens (in [TTL] mode) or the photocells on the
remote flash units ([ q A] mode). Otherwise light from the flash units
may interfere with exposure.
•
Even if [--] is selected for [Master flash] > [Mode], the master flash may
emit low-intensity timing flashes. These flashes may appear in
photographs taken at short range. This can be prevented by choosing
low ISO sensitivities or small apertures (high f-numbers).
•
After positioning the remote flash units, take a test shot and view the
results in the camera display.
Optical AWL
655