Nikon SB-500 AF Speedlight - Manual (Page 45)

E
- 4
E
Wireless Multiple Flash-unit Photography
v
Notes on canceling the flash of the master flash unit
When the master flash unit flash function is canceled and only the
remote flash units fire, the master flash unit emits a number of weak
light signals to trigger the remote flash units. This operation will
normally not affect the correct exposure of the subject, although
the exposure might be affected if the subject is close and a high ISO
sensitivity has been set. To limit this effect, tilt up the master flash
unit’s flash head.