Canon EOS-1D X Mark III Af Setting Manualbook page 79

+ Tracking AF, Eye Detection AF
When [ + Tracking AF] is selected,
more accurate focusing on people can be
achieved by using Eye Detection AF and
head detection.
If [ + Tracking AF], [Large Zone AF], or [Zone AF] is set
to[AF priority(People) : Enable] in [Subject tracking settings],
the camera will actively use face detection and head
detection AF to perform subject tracking. This is an effective
function when you want to continually focus track an
athlete's head during sports.
If [Eye Detection AF] is set to [Enable], you can use the Eye
Detection AF to focus on people's eyes. Eye Detection AF
is effective when you want to focus on the eyes with high
precision in conditions with a shallow depth of field. The
AF area for Live View is extremely wide, so even if there
are eyes at the periphery of the screen, it is possible to
focus on the eyes with high precision. Since it also functions
simultaneously with head detection, accurate AF is provided
by using head detection even in scenes where the eye
appears and disappears due to movement of the subject
such as rotation.
[Eye Detection AF] Face Detection and Head
Detection AF
[Subject tracking settings][AF
priority(People) Enable]
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