Canon EOS R5 Advanced User's Manual page 438

[ ] One-Shot→enabled (magnify)
You can manually adjust the focus after the AF operation if you keep holding down the
shutter button halfway. You can magnify the area in focus and adjust the focus manually
by turning the lens focusing ring.
[ ] Disable in AF mode
Manual focus adjustment is disabled when the lens's focus mode switch is set to
< >.
Caution
With [One-Shot→enabled (magnify)], display may not be magnified even if you
turn the lens focusing ring while pressing the shutter button halfway immediately
after shooting. If so, you can magnify display by releasing the shutter button,
waiting for [ ] display, then pressing the shutter button halfway as you turn the
lens focusing ring.
Note
For details on your lens's manual focus specifications, refer to the Lens Instruction
Manual.
438