Nikon D300 User Manual page 721

AF-Area Modes in Detail
The AF-area modes are designed to give you control over
how many AF points are in use at one time. These modes
offer various ways to track subject movement.
Figure 11-4 shows the AF-area mode selector in the
Single-point AF position.
Figure 11-4. AF-area mode selector at Single-point AF
Single-point AF
This mode uses a single AF point out of the array of 51 points
to acquire good focus. As mentioned before, you can control
which AF point is used by selecting it with the Multi Selector.
In Figure 11-5, notice that the center AF point (of the 51
sensor points) is the one that provides focus information.
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