Canon EOS-1D X Mark III Af Setting Manualbook page 14

Select from [Case 1] to [Case 4] or
[Case A] according to the scene.
Different presets to match the characteristics of the type
of subject movement, and the shooting conditions, can
be selected from [Case 1] - [Case 4] or [Case A]. By simply
selecting one of these cases, suitable settings for the AI
Servo AF and it's Servo AF characteristics that match the
scene will be used.
These four presets are combinations of the following two
parameters,[Trackingsensitivity]and[Accel./decel.tracking]
(see P. 30 – 38 for more details ). In addition, in [Case A],
as the camera analyzes the shooting scene and automatically
sets [Tracking sensitivity] and [Accel./decel. tracking], this
setting covers a wide range of shooting scenarios.
[Case 1] to [Case 4] and [Case A] must be set separately
for viewfinder shooting and Live View shooting.
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