Canon EOS R5 Advanced User's Manual page 352

Caution
Movie digital IS will not function when the lens's optical Image Stabilizer switch is
set to < >.
With non-IS lenses, setting [
mode] to [On].
Although movies can also be recorded with Movie digital IS when using EF-S
lenses or movie cropping, the image area is further reduced.
With a lens whose focal length is longer than 1000 mm, Movie digital IS will not
function.
Stabilization by Movie digital IS may be less effective at some movie recording
sizes.
The wider the angle of view (wide angle), the more effective the image stabilization
will be. The narrower the angle of view (telephoto), the less effective the image
stabilization will be.
When using a tripod, setting Movie digital IS to [Off] is recommended.
Depending on the subject and shooting conditions, the subject may blur noticeably
(the subject momentarily looks out of focus) due to the effects of the Movie digital
IS.
Consider setting to [Off] when using a TS-E lens or fish-eye lens.
Since Movie digital IS magnifies the image, the image looks more grainy. Noise,
dots of light, etc. may also become noticeable.
Note
For details on configuring image stabilization for still photo shooting, see
Stabilizer (IS Mode).
With some lenses, even more effective stabilization (indicated by "+" next to the IS
icon) is possible when the lens's IS is used in conjunction with [IS mode] and
[Movie digital IS] on the camera. For details on lenses compatible with this feature,
visit the Canon website.
Digital IS] to [On] or [Enhanced] also sets [IS
352
Image