Canon EOS ELAN7NE-30V Instructions Manual page 86

Custom Function Settings
C.Fn-05 Mirror lockup
0 : Disabled (Normal operation)
1 : Enabled
Effective for close-up and telephoto shots to prevent camera shake
caused by the mirror's reflex action. See page 75 to use this
feature.
C.Fn-06 Shutter curtain sync with built-in flash/EOS-dedicated Speedlite
0 : 1st-curtain sync
1 : 2nd-curtain sync
With second-curtain sync and a slow shutter speed, you can
create a light trail following a moving subject. The flash fires right
before the shutter closes. Second-curtain sync can be set even
with EOS-dedicated Speedlites which cannot switch the shutter
curtain synchronization. The Speedlite with a shutter curtain
synchronization setting will override the camera's setting.
C.Fn-07 AF-assist beam emission / Main flash firing
The AF-assist beam from the camera and the EOS-dedicated
Speedlite can be enabled/disabled, and the flash from the camera and
EOS-dedicated Speedlite can be enabled/disabled.
0 : Enable AF-assist and flash
1 : Disable AF-assist and enable flash
2 : Enable AF-assist only with EOS Speedlite and enable flash
3 : Enable AF-assist and disable flash
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