SSelecting the AF Point
Selecting with the Dial
To select a horizontal AF point, turn the <6> dial.
To select a vertical AF point, turn the <5> dial.
If all the peripheral AF points light up, automatic AF point selection will take effect.
With [8C.Fn III -10: Selectable AF point], the selectable AF points can be limited to 19 or 11 AF points or to the inner or outer 9 AF points (p.223).
With [8C.Fn III -8: AF expansion w/selected pt], you can change the AF expansion to the left/right AF points, surrounding AF points, or all 45 AF points (p.222).
If you use a super telephoto lens equipped with an Image Stabilizer and AF stop button, when [8C.Fn III -6: Lens AF stop button function] is set to [7: Spot AF], spot AF will be possible (p.220).
By registering the AF point you use frequently, you can switch to it instantly by setting C.Fn III -11-1/2 (p.224) or C.Fn III -6-6 (p.220).
If focus cannot be achieved with the external, EOS-dedicated Speedlite’s AF-assist beam, select the center AF point.
Lens’ Maximum Aperture and AF Sensitivity
With the EOS-1D Mark IV, higher precision AF is possible with a maximum aperture brighter than f/2.8 on a lens or when combined with an Extender.