Focus Mode (Single Servo, Continuous Servo, And Manual) - Nikon D300 Complete Manual

V1.02
things—how the firmware interacts with the hardware to
control where and how focus is achieved.

Focus Mode (Single Servo, Continuous Servo, and Manual)

You set the type of focusing you want the camera to use by
moving the Focus Mode lever on the front of the camera to:
C Continuous Servo autofocus—when you press or partially
press the shutter release the camera focuses the lens. On a full
shutter release press, the shutter normally opens for the
picture even if focus has not yet been achieved. If the Focus
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Confirmation indicator shows in the viewfinder with the
shutter release held partway down, focus follows the subject
until you fully press or let go of the shutter release.
S Single Servo autofocus—when you press or partially press
the shutter release the camera focuses the lens. On a full
shutter release press, the shutter normally does not operate
until focus has been achieved.
M Manual Focus—the D300 does not attempt to focus the
lens and pictures are always taken immediately when the
shutter release is fully pressed. (The viewfinder still displays
the autofocus confirmation information, though, which is
useful in verifying focus in some situations.)
When you press the shutter release (or hold it halfway down),
the viewfinder always indicates the status of the autofocus
system (even in manual focus mode):
The subject is in focus
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Thom Hogan's Complete Guide to the Nikon D300 Page 384