Canon EOS-1D X Mark III Af Setting Manualbook page 46

Auto selection AF
This mode can only be selected during viewfinder
shooting. All AF points are used with this mode, and
the camera selects and focuses automatically.
Viewfinder shooting
+ Tracking AF
This mode can only be selected during Live View
shooting. Within the AF-enabled area up to
approximately 90% horizontally and 100% vertically
of the image area, the camera automatically focuses
with priority on + Tracking.
The frame will display
when a face is detected.
46 46
Live View shooting