If [On] is selected when the camera is used with an optional flash unit that supports the Nikon Creative Lighting system, pressing a control to which [Preview] has been assigned using Custom Setting f2 [Custom controls] will emit a modeling flash.

A Custom Settings: Fine-Tuning Camera Settings

a: Autofocus

b: Metering/Exposure

c: Timers/AE Lock

d: Shooting/Display

e: Bracketing/Flash

f: Controls

g: Movie