Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 739)

2.
Set the recording method.
/ separate
Select [ Enable ] for automatic configuration of the recording method for
still photos and movies. Still photos are recorded to card and
movies to card . Still photo shooting is not possible if card is full
or not inserted. Movie recording is not possible if card is full or not
inserted.
Caution
Specifying [ Enable ] will make [ Rec options ], [ Rec
options ], [ Record/play ], and [ Record/play ]
unavailable.
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