SSelecting the AF Point
Maximum f/stop: Up to f/2.8
With the 39 AF points indicated by 
, high-precision, cross-type AF (both horizontal- and vertical-line sensitive) is possible during manual AF point selection. The cross-type sensors’ vertical-line sensitivity is approx. two times higher than their horizontal-line sensitivity. The remaining six AF points will be horizontal-line sensitive.
During automatic AF point selection, the number of cross-type AF points will decrease from 39 points to the 19 points indicated with 
. The remaining 26 AF points
will be horizontal-line sensitive.
Maximum f/stop: f/4
High-precision, cross-type AF with the center AF point is possible. The remaining 44 AF points will be horizontal-line sensitive only.
Maximum f/stop: f/5.6 or f/8
With f/5.6 lenses, all the AF points will be horizontal-line sensitive only. With f/8 lenses, AF will be possible with the center AF point being horizontal-line sensitive only. AF will not work with the other AF points.
In the case of zoom lenses whose maximum aperture varies depending on the lens focal length, the AF points will be horizontal-line sensitive only (They will not work as cross-type points). However, with the EF28-80mm f/2.8-4L USM lens, cross-type AF will work with the center AF point. With the EF24mm f/2.8 or EF28mm f/2.8 lens, the three AF points on the extreme left and right of the Area AF frame will be horizontal-line sensitive (They will not work as cross-type points).
The following lenses and lens combinations have a maximum aperture of f/4, but cross-type focusing on 39 AF points is still possible as with lenses having an f/2.8 maximum aperture.
EF17-40mm f/4L USM, EF24-105mm f/4L IS USM, EF70-200mm f/2.8L IS USM + Extender EF1.4X II, EF200mm f/2L IS USM + Extender EF2X II, EF300mm f/2.8L IS USM + Extender EF1.4X II, EF400mm f/2.8L IS USM + Extender EF1.4X II
