Canon EOS-1D X Mark III Advanced User's Manual page 305

[ 4]
HDMI display
You can specify how movies are displayed as they are recorded via HDMI to an external
device. Movie output itself is either 4K or Full HD, depending on the [Movie rec. size]
setting.
The default setting is [
+
• Enables movie display both on the camera screen and on the other device, via
HDMI output.
• Camera operations such as image playback or menu display are shown on the other
device via HDMI, not on the camera.
• Deactivates the camera screen during output via HDMI, so that the screen is blank.
• Shooting information, AF points, and other information is shown on the external
device via HDMI, but you can stop output of this information by pressing the
< > button.
• Before recording movies externally, confirm that no information is being sent by the
camera by making sure no shooting information, AF points, and so on is displayed
on external monitors or other devices.
+ ].
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