Canon EOS 7D Mark II (G) Instruction Manual page 454

83: Custom ControlsN
: Metering start
When you press the shutter button halfway, only the exposure metering
is performed.
: AE lock
When you press the button assigned to this function, you can lock the
exposure (AE lock) during metering. Convenient when you want to
focus and meter the shot at different areas or when you want to take
multiple shots at the same exposure setting.
: AE lock (while button pressed)
The exposure will be locked (AE lock) while you press the shutter
button.
: AE lock (hold)
When you press the button assigned to this function, you can lock the
exposure (AE lock). The AE lock will be maintained until you press the
button again. Convenient when you want to focus and meter the shot at
different areas or when you want to take multiple shots at the same
exposure setting.
: AE lock, AF stop
When you press the button assigned to this function, you can lock the
exposure (AE lock) and the AF will stop. Convenient during AI Servo AF
if you want AE lock at the same time when AF stops.
: FE lock
During flash photography, pressing the button assigned to this function
will fire a preflash and record the required flash output (FE lock).
If you assign [AE lock (while button pressed)] to the shutter button, any
buttons assigned to [AE lock] or [AE lock (hold)] will also work as [AE lock
(while button pressed)].
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