Canon EOS R3 Advanced User's Manual page 284

3.
Select [Still photo IS].
Caution
[ : IS (Image Stabilizer) mode] is not displayed when an IS-equipped lens is
attached.
In some cases, this may not provide sufficient stabilization for certain lenses.
Note
For details on image stabilization for movie recording, see
Focal Length
Image stabilization based on your specified lens focal length is possible by setting the focal
length when using lenses that do not support lens communication.
[Always]: Provides constant image stabilization.
[Only for shot]: Image stabilization is active only at the moment of
shooting.
284
Movie Digital IS.