Canon EOS R Advanced User's Manual page 214

Shooting Movies
For movie shooting, the ISO speed cannot be expanded to L (equivalent
o
to ISO 50).
When switching from still photo shooting to movie shooting, check the
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camera settings again before shooting movies.
During movie shooting, avoid changing the shutter speed or aperture.
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Doing so may record the changes in the exposure or create more noise
at high ISO speeds.
When shooting a movie of a moving subject, a shutter speed of approx.
o
1/25 sec. to 1/125 sec. is recommended. The faster the shutter speed,
the less smooth the subject's movement will look.
If you change the shutter speed while shooting under fluorescent or LED
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lighting, image flicker may be recorded.
With ISO Auto, exposure compensation can be set in a range of ±3
o
stops.
When ISO Auto is set, you can press the < A > button to lock the ISO
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speed. After locking the ISO speed during movie shooting, you can
cancel it by pressing the < S > button. (ISO speed lock is maintained
until you press the < S > button.)
If you press the < A > button and recompose the shot, you can see the
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exposure level difference on the exposure level indicator compared to
when the < A > button was pressed.
With the camera ready to shoot in the [ M ] mode, you can display the
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histogram by pressing the < B > button.
You can adjust ISO speed while recording a movie by pressing the
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< B > button and using the < 6 > dial.
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