vNotes 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.
E
Wireless Multiple