Canon EOS-1D X Mark III Advanced User's Manual page 346

(Face)+Tracking:
The camera detects and focuses on people's faces. If a face moves, the AF point <
also moves to track the face.
You can set [ : Eye Detection AF] to [Enable] to shoot with the subject's eyes in focus
( ).
1.
Check the AF point.
An AF point < > appears over any face detected.
If < > is displayed, you can use <
on.
Press < > to move the AF point to the center of the screen.
> to choose a face to focus
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