Canon EOS-1D X Mark III Advanced User's Manual page 392

Note
Available when [
set to [Spot AF] or [1-point AF].
Operation when [
point AF] is equivalent to setting [AF speed] to [Standard(0)].
An asterisk "*" to the right of [
default setting has been modified.
Movie Servo AF track sens.
You can adjust the tracking sensitivity (to one of seven levels), which affects responsiveness
if the subject strays from the AF point during Movie Servo AF, as when interfering objects
move across AF points or when you pan.
Locked on: –3/–2/–1
With this setting, the camera is less likely to track a different subject if the main subject
strays from the AF point. The closer the setting is to the minus (–) symbol, the less the
camera is inclined to track a different subject. It is effective when you want to prevent
the AF points from rapidly tracking something that is not the intended subject during
panning or when an obstacle cuts across the AF points.
Responsive: +1/+2/+3
This makes the camera more responsive when tracking a subject that covers the AF
point. The closer the setting is to the plus (+) symbol, the more responsive the camera
is. It is effective when you want to keep tracking a moving subject as its distance from
the camera changes or to rapidly focus on another subject.
Note
Available when [
set to [Spot AF] or [1-point AF].
With [ : AF method] set to an option other than [Spot AF] or [1-point AF],
operation is equivalent to a setting of [0].
: Movie Servo AF] is set to [Enable] and [
: AF method] is set to an option other than [Spot AF] or [1-
: Movie Servo AF speed] indicates that the
: Movie Servo AF] is set to [Enable] and [
392
: AF method] is
: AF method] is