Canon EOS 80D - Manual (Page 127)

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The camera’s AF sensor has 45 AF points. The illustration below shows
the AF sensor pattern corresponding to each AF point. When using
lenses with a maximum aperture of f/2.8 or faster, high-precision AF is
possible with the center AF point in the viewfinder.
AF Sensor
The focusing sensor is geared to obtain higher precision
focusing for lenses with a maximum aperture of f/2.8 or
faster. A diagonal cross pattern makes it easier to focus on
subjects difficult for AF. It is provided at the center AF point.
The focusing sensor is geared for lenses with a maximum
aperture of f/5.6 or faster (and some f/8 lenses). Since it
has a horizontal pattern, it can detect vertical lines. It
covers all 45 AF points.
The focusing sensor is geared for lenses with a maximum
aperture of f/5.6 or faster (and some f/8 lenses). Since it
has a vertical pattern, it can detect horizontal lines. It
covers all 45 AF points.
Depending on the lens attached to the camera, the number of usable
AF points, AF point patterns, the shape of Area AF frame, etc. vary. For
details, see “Lenses and Usable AF Points” on page 128.
Diagram
Cross-type focusing: f/5.6 vertical + f/5.6 horizontal
(also compatible with some f/8 lenses)
Dual cross-type focusing:
f/2.8 right diagonal + f/2.8 left diagonal
f/5.6 vertical + f/5.6 horizontal
(also compatible with f/8 lenses)