Canon EOS-1DX MARK II Settings Manual page 74

Automatic selection: EOS iTR AF
[EOS iTR AF (Face priority)]
The RGB color metering system prioritizes detection of
human faces, and combines with the 61-point AF system
to keep focus upon faces, even if they move around the
AF array. In scenes without faces, it defers to using the
initially-detected subject's shape and color.
[EOS iTR AF]
The 360,000 pixel RGB color metering system still can
detect faces, but now prioritizes color information to
maintain AF coverage with moving subjects. This may
be a better choice, with [Auto selection AF], [Large
Zone AF], and [Zone AF], if faces are not a prominent
part of the subject (such as photographing birds,
vehicles, athletes with helmets, etc.).
[Disable]
This performs AF point selection and subject tracking
with only sharpness information from the AF system,
and does not apply color or face detection info from the
RGB color metering system.
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