Canon EOS-1D X Mark III Advanced User's Manual page 270

Information Display (Movie Recording)
For details on the icons on the movie recording screen, see
Caution
Precautions for movie recording
Do not point the camera toward an intense light source, such as the sun or an
intense artificial light source. Doing so may damage the image sensor or the
camera's internal components.
If you record something that has fine detail, moire or false colors may result.
If < > or <
movie recording, the white balance may also change.
If you record a movie under fluorescent or LED lighting, the movie image may
flicker.
If you perform AF with a USM lens during movie recording in low light, horizontal
banding noise may be recorded in the movie. The same type of noise may occur if
you focus manually with certain lenses equipped with an electronic focusing ring.
Recording a few test movies is recommended if you intend to perform zooming
during movie recording. Zooming as you record movies may cause exposure
changes or lens sounds to be recorded, an uneven audio level, inaccurate lens
aberration correction, or loss of focus.
Large aperture values may delay or prevent accurate focusing.
Performing AF during movie recording may cause the following kinds of issues:
significant temporary loss of focus, recording of changes in movie brightness,
temporary stopping of movie recording, or recording of mechanical lens sounds.
Avoid covering the built-in movie microphone with your fingers or other objects.
Connecting or disconnecting an HDMI cable during movie recording will end
recording.
Also see General Movie Recording
Also see General Live View Shooting
> set and the ISO speed or aperture value changes during
Precautions.
Precautions, as needed.
270
Information Display.