Canon EOS R10 User Manual page 495

Use as a focusing or control ring
Menu-based switching of lens focus/control ring functionality.
Caution
Available when using lenses that have a combination focusing ring/control ring but
have no switch to switch between these features.
Use as focus ring
The ring works as a focusing ring.
Use as control ring
The ring works as a control ring.
Note
Switching is also possible from the Quick Control screen, when customized with
[ : Customize Quick Controls] ( ).
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