Nikon D300 User Manual page 765

We'll examine each of the settings available under the
Commander mode. TTL is the easiest to use since it allows
you to set exposure compensation for the built-in flash as well
as each of your flash groups. Next, we'll look at M mode,
since that gives you fine control of your flash from full-power
(1/1) to 1/128 power. We'll briefly look at AA mode. Then
finally, we'll consider the - - (double-dash) mode, which
prevents the camera's built-in flash from firing the main flash
output but does not stop the necessary monitor pre-flashes,
nor the firing of the external flash units.
Figure 12-10. Commander mode setup screens
When your camera is controlling external Speedlights using
its built-in Commander mode, you must always raise the
built-in flash on your D300(S). The camera communicates
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