Canon EOS-1DX Af Setting Manualbook page 115

Example:
Switch AI Servo AF characteristics with
the button and button
When you assign functions to the and buttons,
those two adjacent buttons can be used to instantly
switch functions for shooting. For example, when
assigning the two often used AI Servo AF characteristics
(Cases) , it is possible to switch to the optimal AI Servo
AF characteristics depending on the subject and if any
obstructions may enter the frame.
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