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 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 dial to set the exposure
compensation or the aperture for manual exposure.
2: ISO speed
You can turn the 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 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 and buttons will be switched between
them. By holding down the 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 buttons will be switched between
them. By holding down the button and turning the diai,
you can set the exposure compensation or aperture.
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