Nikon D3X User Manual page 176

Measuring a Value for White Balance
1
Light a reference object.
Place a neutral gray or white object under the lighting that will
be used in the final photograph. In studio settings, a standard
gray panel can be used as a reference object. Note that
exposure is automatically increased by 1 EV when measuring
white balance; in exposure mode h, adjust exposure so that
the electronic analog exposure displays shows ±0 (pg. 122).
2
Set white balance to L ([Preset manual]).
Press the WB button and rotate the main command dial until
L is displayed in the rear control panel.
r
150
WB button Main command dial Rear control panel