Canon EOS-1D X Mark III Advanced User's Manual page 362

Case 2: Continue to Track Subjects, Ignoring Possible
Obstacles
Setting to continue focusing on the subject even if non-subjects move across AF points, or if
the subject strays from AF points. Effective if you prefer the focus not to switch to non-
subjects or the background.
Note
Try setting [Tracking sensitivity] to [–2] if non-subjects tend to steal the focus or
AF points tend to stray from the subject much of the time, preventing the camera
from tracking the target subject under default settings (
Default
• Tracking sensitivity: Locked on: –1
• Accel./decel. tracking: 0
362
).