AF Area Selection Modes
If [8C.Fn III -12: Orientation linked AF point] is set to [1: Select different AF points], you can set the AF area selection mode and manually-selected AF point (or zone in the case of Zone AF) separately for vertical and horizontal shooting (p.230).
If [8C.Fn III -10: Focus display in AI SERVO/MF] is set to [Disable], the active AF points <S> during AI Servo AF will not be displayed.
Lens’ Maximum Aperture and AF Sensitivity
With lenses whose maximum aperture is larger than f/5.6
With all AF points, cross-type AF sensitive to both vertical and horizontal lines is possible. With the following lenses, the peripheral AF points will be vertical- line or horizontal-line sensitive only. (They will not work as cross-type points.)
List of the lenses with which peripheral AF points will become vertical-line or horizontal-line sensitive
Cross-type AF
Vertical-line sensitive AF
Horizontal-line sensitive AF
With the lenses listed below, cross-type AF is not possible with < 
> and <
> AF points.
EF35-80mm f/4-5.6, EF35-80mm f/4-5.6 II, EF35-80mm f/4-5.6 III, EF35- 80mm f/4-5.6 USM, EF35-105mm f/4.5-5.6, EF35-105mm f/4.5-5.6 USM, EF80-200mm f/4.5-5.6 II, EF80-200mm f/4.5-5.6 USM
With lenses whose maximum aperture is larger than f/2.8*
With the center AF point, high-precision, cross-type AF sensitive to both vertical and horizontal lines is possible. The center AF point’s sensitivity to vertical and horizontal lines is about twice as sensitive as the other AF points.
The remaining 18 AF points will work as cross-type points with lenses brighter than f/5.6.
* Except with the EF28-80mm f/2.8-4L USM and EF50mm f/2.5 Compact Macro lenses.
