Canon EOS R3 Advanced User's Manual page 983

Movie recording stops by itself.
If the card's writing speed is slow, movie recording may stop automatically. For details
on cards that can record movies, see
card's writing speed, refer to the card manufacturer's website, etc.
Perform low-level formatting to initialize the card if the card's writing or reading speed
seems slow (
Movie recording stops automatically if you record a high frame rate movie for 89 min. 29
sec.
The ISO speed cannot be set for movie recording.
ISO speed is set automatically in [
set the ISO speed (
The minimum speed in the ISO speed range is ISO 200 when [
priority] is set to [Enable] or [Enhanced].
Expanded ISO speeds cannot be selected for movie recording.
Check the [ISO speed range] setting under [
Expanded ISO speeds are not available when [
[Enable] or [Enhanced].
The exposure changes during movie recording.
If you change the shutter speed or aperture value during movie recording, the changes
in the exposure may be recorded.
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, or loss of focus.
The image flickers or horizontal stripes appear during movie recording.
Flickering, horizontal stripes (noise), or irregular exposures can be caused by
fluorescent lighting, LED lighting, or other light sources during movie recording. Also,
changes in the exposure (brightness) or color tone may be recorded. In [
using a slower shutter speed may reduce the problem.
).
).
Card performance requirements. To find out the
] recording mode. In [
: ISO speed settings].
: Highlight tone priority] is set to
983
] mode, you can manually
: Highlight tone
] mode,