Canon EOS 5D MARK IV Instruction Manual page 77

Before You Start
If you format a CF card exceeding 128 GB or SDXC card with this
camera and then insert it into another camera, an error may be displayed
and the card may become unusable. Certain computer operating
systems or card readers may not recognize a card formatted in exFAT.
When the card is formatted or data is erased, only the file management
information is changed. The actual data is not completely erased. Be
aware of this when selling or discarding the card. When discarding the
card, perform low-level formatting or destroy the card physically to
prevent personal data from being leaked.
The card capacity displayed on the card format screen may be smaller
than the capacity indicated on the card.
This device incorporates exFAT technology licensed from Microsoft.
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