Canon EOS 70DN Basic Instruction Manual page 551

: AE lock
When you press the button assigned to this function, you can lock the
exposure (AE lock) during the 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.
: FE lock
During flash photography, pressing the button assigned to this function
will fire a preflash and record the required flash output (FE lock).
: Set ISO speed (hold button, turn
You can set the ISO speed by holding down <0> and turning the
<6> dial.
If Auto ISO is set, manual ISO speed setting will take effect. Auto ISO
cannot be set. If you use this function in the <a> mode, you can adjust
the exposure with the ISO speed while maintaining the current shutter
speed and aperture.
: Shutter speed setting in M mode
In manual exposure <a>, you can set the shutter speed with the
<6> or <5> dial.
: Aperture setting in M mode
In manual exposure <a>, you can set the aperture with the <6> or
<5> dial.
8: Custom Controls
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