Single
Area AF: Only one of the AF sensors is used
for AF. The sensor is user-selected. To allow predictive focus
tracking to operate with moving subjects, the sensor must
be kept positioned over the subject. If the sensor drops off
the subject, the camera AF mechanism will start focusing on
the area now positioned in front of the sensor. The camera
may try to focus on areas in the foreground or background
and in low contrast situations may hunt and search. The Nikon
instruction manual recommends Single Area AF for relatively
static subjects or with moving subjects that can be easily
kept within active focus sensor.
Dynamic
Area AF: Focusing begins with
the user-selected AF sensor but the camera will switch focus
to other sensors to follow a moving subject. If the subject
moves onto an adjacent sensor, predictive focus will track
its movement and AF activity will be transferred to sensor
positioned over the subject. Nikon recommends Dynamic Area
AF for erratically or rapid moving subjects—situations
where it may be difficult to keep a single active sensor positioned
on the subject.
Group
Dynamic AF: Group Dynamic
AF is the most complex of the AF Area Modes. Instead of selecting
a single initial focusing sensor, the user selects a group
of sensors. CSM a3 determines the number/shape of sensors
in the group (the pattern) and how initial focus acquisition
is achieved (center sensor or closest subject). Nikon recommends
Group Dynamic AF for erratically or rapid moving subjects
— in situations when one knows the general area within
frame where the action will occur.
CSM
a3 Options are Pattern 1/Center Sensor, Pattern 1/Closest
Subject, Pattern 2/Center Sensor, and Pattern 2/Closest Subject
Pattern:
Either a diamond/triangular pattern of four/five sensors (Pattern
1) or a row/triangular pattern of three/four sensors (Pattern
2) can be selected (see figures below).
Initial Focus Acquisition:
Center Sensor or Closest Subject.
With Center Sensor selected by CSM a3, initial
focus acquisition will be performed with the center sensor
of the user-selected group but can automatically switch to
other sensors in the group if the subject moves. Using center
sensor does limit initial focus acquisition to only five of
the eleven AF sensors (the center sensor of each group). Dynamic
Area AF, on the other hand, allows any one of the eleven sensors
to be selected for initial focus acquisition.
In
Closest Subject Priority, the camera will analyze contrast
and distance information in front of each sensor of the selected
group and will attempt to focus on the closest subject. When
one presses the focus button the selected group of sensors
will light up in red briefly. In AF-S mode, the sensor that
acquires focus will blink in red briefly once AF is achieved.
In AF-C mode, the sensor used to set focus will blink in red
briefly after photo is taken.
