Canon EOS 5D Instruction Manual page 199

C.Fn III -6
0: Disable
1: Enable
Prevents camera vibrations caused by the reflex mirror action which can
disturb shooting with super telephoto lenses or close-up (macro)
shooting. See page 101 for the mirror lockup procedure.
C.Fn III -7
0: Disable
1: Enable
When you select AI Servo AF and the center AF point, the six Assist AF
points (p.80) will also function. Seven AF points will track the subject.
This is effective for subjects that move erratically, making it difficult for
only the center AF point to track it.
Mirror lockup
AF point area expansion
3 Custom Function SettingsN
199