Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 858)

2.
Select a camera control.
3.
Select a function to assign.
Press < > to set it.
You can configure advanced settings for functions labeled with
in the lower left of the screen by pressing the <
> button.
Note
Default settings can be restored by pressing the < > button with the screen in
step 2 displayed. Note that [ 6 : Custom Controls ] settings are not cleared even
if you select [ 9 : Clear all Custom Func. (C.Fn) ].
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