Canon EOS 5D Mark IV Instruction Manual page 41

If necessary, also read "NFC Function Cautions" (p.25).
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While saving images, a picture cannot be taken even if the camera's

shutter button is pressed.
Do not drop the camera on Connect Station or touch the camera to it with

too much force. Doing so may damage Connect Station's internal hard
disk.
If the camera is not recognized right away, try holding it close to Connect

Station and slowly moving it or rotating it horizontally.
Just holding the camera close to Connect Station may not establish a

connection. In such a case, gently touch Connect Station with the
camera.
When holding the camera close to Connect Station, do not leave
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anything between the camera and Connect Station. In addition, when a
case is attached to the camera, communication may not be possible via
NFC function.
If the camera and Connect Station are moved too far away from each

other while saving images, saving may take time or the connection may
be terminated.
If the camera's battery runs out while saving images, saving will stop.
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Charge the battery, then try again.
4K movies cannot be played back with Connect Station.
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When all images are already saved, saving will not be performed. In
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such a case, select [OK] to terminate the connection.
When there are a large number of images on the memory card, it may

take time to check and save the images.
While saving images, the camera's auto power off does not function.
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Saving Images
41