Nikon D300 User Manual page 640

If you want to experiment with fine-tuning your Matrix meter
to see what you can get away with, please refer to the chapter
titled Chapter 4, and see the section titled Fine Tune
Optimal Exposure – Custom setting b6 (D300S and D300).
This setting allows you to fine-tune each of the exposure
meters individually in 1/6 stops. I leave my D300(S) set to 3/6
stops overexposure, which equals 1/2 stop. Don't be afraid to
experiment with your D300(S), since you can always change
your fine-tuning back to zero.
You might find that ½ stop is too much for you, or that you
don't need any compensation at all. The point is that you are
not limited with this camera. You can use the Matrix meter
with factory settings or fine-tune endlessly.
Using Flash with Matrix Metering
When you are using flash with Matrix metering, you might
find that the D300(S) is especially conservative. I have used
the built-in pop-up Speedlight, an SB-600, and an SB-800
with my camera, and it consistently underexposes by about
1/3 stop in Matrix metering.
To overcome this perceived tendency in my D300(S), I have
reprogrammed the camera's Fn (FUNC.) button to activate
the Spot meter while I hold the button down (see the section
titled Assign Fn (FUNC.) Button – Custom Setting f5
(D300S) and f4 (D300) in the chapter titled Chapter 4). With
this adjustment, I find that a good spot-reading directly off
my subject gives me nearly perfect exposures using flash.
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