Canon EOS-1D X Mark II DSLR Camera (Body Only) - Manual (Page 98)

AF Area Selection Modes
98
The AF area is divided into three focusing zones (left, center, and right)
for focusing. Since the focusing area is larger than with Zone AF and all
the AF points in the selected zone are used for the automatic AF point
selection, it is superior to single-point AF and AF point expansion in
tracking the subject, and it is effective for moving subjects.
However, since it is inclined to focus on the nearest subject, focusing on
a specific target is may be more difficult.
The AF point(s) achieving focus is displayed as <
S >.
The Area AF frame (entire AF area) is used to focus. The AF point(s)
achieving focus is displayed as <
S >.
With One-Shot AF, pressing the shutter button
halfway will display the AF point(s) <
S > that
achieved focus. If multiple AF points are
displayed, it means they all have achieved focus.
This mode tends to focus on the nearest subject.
With AI Servo AF, you can set the AI Servo AF’s
initial position with [
f 4: Initial AF pt, AI
Servo AF ] (p.134). As long as the Area AF frame
can track the subject during shooting, focusing
will continue.
Large Zone AF (Manual Zone Selection)
Automatic selection AF