Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 937)

Button Operations on the Quick Control/Custom Quick
Control Screen
Press the < >/< >/< >/< >/< >/< >/< >
buttons to access the corresponding setting screen, then use < >/< >/< >/
< > to set the function.
Shooting mode
AF operation/drive mode
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