Canon EOS 5D Mark IV Instruction Manual page 33

If necessary, also read "NFC Function Cautions" (p.25).
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When touching the smartphone to the camera, be careful not to drop the

camera or smartphone.
Do not touch the smartphone to the camera with too much force. Doing

so can scratch the camera or smartphone.
Just holding the smartphone close to the mark may not establish a

connection. Be sure to touch the mark with the smartphone so that they
come into contact with each other.
Recognition may be difficult depending on the smartphone. Touch slowly
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while changing the position or rotating horizontally.
Another application on the smartphone may start depending on how you

touch. Check the position of the P mark, then touch again.
When touching the smartphone to the camera, do not leave anything
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between the camera and smartphone. In addition, when a case is
attached to the camera or smartphone, communication may not be
possible via NFC function.
The camera cannot be connected to two or more smartphones at the

same time.
By default, the connection settings with the NFC function are saved as

the fourth setting (a setting dedicated to NFC connection) under the
name [SET4(NFC)]. When you connect the camera to another
smartphone via NFC, [SET4(NFC)] will be overwritten.
While connected, the camera's auto power off does not function.

Connecting to an NFC-enabled Smartphone
33