Canon RF 35mm F1.4 L VCM Instructions Manual page 12

5. Lens Function Button (AF Stop Button)
In the default settings, the lens function button
serves as a AF stop button. You can assign
different functions to the button from the
[Customize buttons] section of the camera.
Please refer to the camera's instructions for
details.
Lens function button
(AF stop button)
Use as a AF stop button
During autofocus operation, you can press an
AF stop button to temporarily pause autofocus,
and then release the button to resume.
Press an AF stop button to maintain a focusing
distance or to avoid focus search.
Press the shutter button while holding down
an AF stop button to shoot at that focusing
distance.
Useful when autofocus is operating mostly in
z
Servo AF.
ENG-11