Nikon D300S (Body Only), D300s user manual 265, Option Description Points, 3D-tracking

Option	Description
d 21 points	If the subject leaves the selected focus point, the
	camera will focus based on information from the
	surrounding 20 focus points. Choose when
	photographing subjects that are moving
	unpredictably (e.g., players at a football game).
e 51 points	If the subject leaves the selected focus point, the
	camera will focus based on information from the
	surrounding 50 focus points. Choose when
	photographing subjects that are moving quickly and
	can not be easily framed in the viewfinder (e.g., birds).
	If the subject leaves the selected focus point, the
	camera will use 3D-tracking to track the subject and
f 51 points	select a new focus point as required. Use to quickly
	compose pictures with subjects that are moving
(3D-tracking)
	erratically from side to side (e.g., tennis players). If the
	subject leaves the viewfinder, remove your finger from
	the shutter-release button and recompose the
	photograph with the subject in the selected focus
	point.

A3D-tracking

When the shutter-release button is pressed halfway, the colors in the area surrounding the focus point are stored in the camera. Consequently 3D-tracking may not produce the desired results with subjects that are the same color as the background or that occupy a very small area of the frame.

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