Canon EOS-1DX Af Setting Manualbook page 108

Set up steps
[Register/apply shooting functions]
Assign [Register/apply shooting functions] to the
button or the
[Custom Controls]. Press the
function's selection screen, (various functions can be set)
and select the [AF area selection mode] that you want to
use.
Assign to the
button, or the
to [Register/apply
shooting functions]
Press the
Select the [AF area
selection mode]
button with the custom function's
108
button
button on the assign
button