Canon EOS-1D Mark IV - Manual (Page 210)

Custom Function Settings
C.Fn I -7 Spot metering link to AF point
0; Disable (use center AF point)
1: Enable (use active AF point)
If [.IS.C.Fn III -10: Selectable AF point] (p.223) is set to [1 : 19 points],
[2:11 points], [3: Inner 9 points] or [4: Outer 9 points], spot metering
linked to the selected AF point is possible. With automatic AF point
selection, spot metering will be at the viewfinder center.
41 If C.Fn III -10 is set to [0: 45 points], spot metering at the center will be set
even if C.Fn I -7 is set to [1: Enable (use active AF point)].
C.Fn I -8 Safety shift
0: Disable
1: Enable (Tv/Av)
This works in the shutter-priority AE (Tv) and aperture-priority AE (Av)
modes. When the subject's brightness changes erratically and the
correct autoexposure cannot be obtained, the camera will change the
exposure setting automatically to obtain a correct exposure.
2: Enable (ISO speed)
This works in the Program AE (P), shutter-priority AE (Tv), and
aperture-priority AE (Av) modes. When the subject’s brightness
changes erratically and the correct autoexposure cannot be obtained,
the camera will change the ISO speed automatically to obtain a correct
exposure.
0 • Even if the exposure settings settable range has been changed with
C.Fn I -3,12,13, the safety shift will override it when necessary to obtain
the correct exposure,
• With settings 1 and 2, safety shift also works with flash.
C.Fn I -9 Select usable shooting modes
Disable: All the shooting modes (M, Tv, Av, P, BULB) will be
selectable.
Enable: Only the shooting modes set with [Register] will be selectable.
Register: To make a shooting mode unselectable, uncheck the checkmark
<>/>. After entering the settings, select [Apply].
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