Nikon D3000 Reference Manual page 60

3
Choose a focus mode.
Highlight one of the following options and press
J. Note that AF-S and AF-C are available only in
modes P, S, A, and M.
Option
Auto-servo
AF-A
AF
Single-servo
AF-S
AF
Continuous-
AF-C
servo AF
MF Manual focus Focus manually (0 48).
D
Continuous-servo Autofocus
In AF-C mode or when continuous-servo autofocus is selected in AF-A mode, the camera gives
z
priority to shutter response and the shutter may be released before the in-focus indicator is
displayed.
A
Getting Good Results with Autofocus
Autofocus does not perform well under the conditions listed below. The shutter release may
be disabled if the camera is unable to focus under these conditions, or the in-focus indicator
(I) may be displayed and the camera may sound a beep, allowing the shutter to be released
even when the subject is not in focus. In these cases, focus manually (0 48) or use focus lock
(0 46) to focus on another subject at the same distance and then recompose the
photograph.
42
Camera automatically selects single-servo autofocus if subject is
stationary, continuous-servo autofocus if subject is moving.
For stationary subjects. Focus locks when shutter-release button
is pressed halfway.
For moving subjects. Camera focuses continuously while shutter-
release button is pressed halfway.
There is little or no contrast
between the subject and the
background.
Example: Subject is the same
color as the background.
The focus point contains
objects at different distances
from the camera.
Example: Subject is inside a
cage.
The subject is dominated by
regular geometric patterns.
Example: A row of windows
in a skyscraper.
Description
The focus point contains
areas of sharply contrasting
brightness.
Example: Subject is half in the
shade.
Background objects appear
larger than the subject.
Example: a building is in the
frame behind the subject.
The subject contains many
fine details.
Example: A field of flowers or
other subjects that are
small or lack variation in
brightness.