Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 743)

Note
With [ Priority: ] set, the camera switches to the priority card when cards are
inserted or removed.
Setting size via the rear LCD panel
1.
Press the < > button ( ).
2.
Select a card.
Turn the < > dial to select a card.
The card labeled with < > is used for recording and playback.
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