Canon EOS-1DX Af Setting Manualbook page 117

When it is difficult to press the button
which could previously be used for assigning
functions
The buttons can easily be used
to switch to One Shot and AI Servo
while looking through the viewfinder
Although it has been possible to assign [ONE SHOT AI
SERVO] to the and buttons, when it is difficult to
press these buttons on the front of the camera, it is
effective to assign this function to the and
buttons. When quick shooting is required, you can now
instantly switch AF modes.
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