Canon EOS-1D Mark IV - Manual (Page 228)

Custom Function Settings
C.Fn IV -3 Quick Control Dial in metering
The Quick Control Dial’s function while the metering is active can be
changed.
0: Exposure compensation/Aperture
1: AF point selection
You can select the AF point directly with the <0> dial without first
pressing the <EE> button. While metering is active, turning the <0>
dial will select a horizontal AF point. Automatic selection cannot be
selected. However, if C.Fn III -12-2 has also been set, automatic
selection can be selected.
Press the <0> button and turn the <i^lQ> dial to set the exposure
compensation or the aperture for manual exposure.
2: ISO speed
You can turn the <Q> dial to change the ISO speed in real-time.
3: AF point selection + H Ti EB
You can select the AF point directly with the <0> dial without first
pressing the <EB> button. While metering is active, turning the <0>
dial will select a horizontal AF point. Automatic selection cannot be
selected. However, if C.Fn III -12-2 has also been set, automatic
selection can be selected.
The functions of the <I2> and <EE> buttons will be switched between
them. By holding down the <EB> button and turning the dial, you
can set the exposure compensation or aperture.
4: ISO speed + 0 ^ ISO
You can turn the <0> dial to change the ISO speed in real-time.
The functions of the <0> and <ISO> buttons will be switched between
them. By holding down the <ISO> button and turning the <izi> diai,
you can set the exposure compensation or aperture.
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