Nikon D300 User Manual page 646

If you spot-meter for the shadows instead, the person's face is
likely to blow out to solid white. We'll discuss this in more
detail in a later section of this chapter when we explore the
histogram.
Use your Spot meter to get specific meter readings of small
areas on and around your subject, make some exposure
decisions yourself, and your subject should be well exposed.
Just remember that the Spot meter evaluates only for the
small area that it sees, so it cannot adjust the camera for
anything except that one tiny area. Spot metering requires
some practice to learn how to use it well, but it is a very
powerful tool to balance exposure values in your images.
For information on fine-tuning Spot metering, see the section
called Fine Tune Optimal Exposure in the chapter titled
Chapter 4.
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