Canon EOS-1DX MARK II Settings Manual page 29

It is possible to focus on subjects that move
erratically in any direction
Inline skating on a half-pipe. Capturing the moments
when the skater is jumping and twisting is easier with
Case 5. Remember: "erratic movement" refer to
subjects that will change location within the frame. Case
5 is able to address this when the camera is using a AF
Area that allows automatic switching from one AF point
to another:
• Automatic AF point selection
• Large Zone AF
• Zone AF
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