Canon EOS 5D MARK IV Instruction Manual page 536

H Using Eye-Fi Cards
Cautions for Using Eye-Fi Cards
If [Wi-Fi/NFC] under [54: Wireless communication settings] [Built-in
wireless settings] is set to [Enable], image transfer with an Eye-Fi card
will not be possible.
If "J" is displayed, an error occurred while retrieving the card
information. Turn the camera's power switch off and on again.
Even if [Eye-Fi trans.] is set to [Disable], it may still transmit a signal. In
hospitals, airports, and other places where wireless transmissions are
prohibited, remove the Eye-Fi card from the camera beforehand.
If the image transfer does not function, check the Eye-Fi card and
computer settings. For details, refer to the card's instruction manual.
Depending on the wireless LAN's connection conditions, the image
transfer may take longer or it may be interrupted.
Because of the communication function, the Eye-Fi card may become
hot.
The camera's battery power will be consumed faster.
During the image transfer, auto power off will not take effect.
If you insert a wireless LAN card other than an Eye-Fi card, [51: Eye-Fi
settings] will not appear. Also, the transmission status icon <H> will not
appear.
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