Canon EOS 5D Mark IV L-series Zoom Lens Kit Owner's Manual

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 Custom Function SettingsN
492
Default Erase option
C.Fn4
During image playback and image review immediately after shooting, 
when you press the <L> button, the erase menu appears (p.439). You 
can set which option, [Cancel] or [Erase], is to be preselected on this 
screen.
If [Erase] is set, you can just press <0> to quickly erase the image.
 : [Cancel] selected
L
  : [Erase] selected
Retract lens on power off
C.Fn4
This is to set the lens retraction mechanism for when a gear-driven 
STM lens (such as EF40mm f/2.8 STM) is attached to the camera. You 
can set it to retract the extended lens automatically when the camera’s 
power switch is set to <2>.
ON : Enable
OFF: Disable
If [Erase] is set, be careful not to erase an image accidentally.
 
With auto power off, the lens will not retract regardless of the setting.
 
Before detaching the lens, make sure that it is retracted.
When [Enable] is set, this function takes effect regardless of the lens’s 
focus mode switch setting (AF or MF).