Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 856)

C.Fn9
Clear all Custom Func. (C.Fn)
Selecting [ 9 : Clear all Custom Func. (C.Fn) ] clears all Custom Function settings.
Note
Customized operations for [ 6 : Custom Controls ], [ 7 : switching ( /
) ], and [ 7 : Smart controller ] are not cleared if you perform [ 9 : Clear
all Custom Func. (C.Fn) ]. Note that although information added using [ 8 : Add
IPTC information ] is retained, the setting changes to [ Disable ].
Settings for [ 3 : AE Microadjustment ] and [ 3 : FE Microadjustment ] are set
to [ Disable ] but not cleared when [ 9 : Clear all Custom Func. (C.Fn) ] is
performed.
856