Nikon D300 Complete Manual page 705

Outdoors, most Nikon users tend to use an a2 adjustment to
the named white balance setting they're using (e.g. Cloudy
a2). Indoors, many just let the camera do its thing, as a bit of
warmth is usually preferred.
Personally, I like having a reference setting, regardless of how
I set my D300. With a reference, I can use Photoshop's color
controls to correct any remaining bias. How do you establish
a reference? I carry a Kodak gray card and an xRite Mini
ColorChecker with me whenever possible, and I take a shot
with both cards in the scene whenever the lighting changes
significantly (it's okay to take this shot using JPEG fine, by
the way—it's one way I identify my color check file, since all
the other files have NEF versions). If I want to use Preset
manual white balance, then I set it using the gray card.
Of course, you don't always want to correct for color
temperature! One reason why sunrise and sunset scenes look
red (or orange) to us is that the color temperature is extremely
warm, approximately 3100-3600K depending upon the exact
timing of the shot and atmospheric conditions. We perceive it
as warm because the change occurs so rapidly (prior to
sunrise the color temperature may be 7000K or higher) and
the blue wavelengths are generally filtered out by the extra
atmosphere the light has to get through. In such cases, you'd
want to set the camera's white balance to Direct sunlight
and shoot normally, lest you lose the very aspects of the light
that intrigued you in the first place.
But probably the most difficult white balance situation to deal
with is mixed sources that include frequency-based lights
(fluorescent, mercury vapor, carbon arc, etc.). As I noted
earlier, you need to set your shutter speed to match
frequency-based lights (e.g. 1/60 for fluorescent lights in the
US), lest you introduce color errors due to phosphor decay.
But that may not be enough. Ask yourself these questions:
• Which lighting type dominates? In mixed source
situations, try turning the sources on one at a time and
Thom Hogan's Complete Guide to the Nikon D300
V1.02
Page 705