Canon EOS 5Ds Instruction Manual page 104

Lenses and Usable AF Points
Group H
AF is possible with the center AF point and the adjacent AF points above,
below, on the left, and on the right. Only the following AF area selection
modes are selectable: Single-point AF (manual selection), Single-point Spot
AF (manual selection), and AF point expansion (manual selection
If an Extender is attached to the lens and the maximum aperture is f/8
(between f/5.6 and f/8), AF will be possible.
If the maximum aperture is smaller than f/5.6 (maximum aperture
number is between f/5.6 and f/8), focus may not be achieved with AF
when shooting low-contrast or low-light subjects.
When Extender EF2x is attached to the EF180mm f/3.5L Macro USM
lens, AF is not possible.
If the maximum aperture is smaller than f/8 (maximum aperture number
exceeds f/8), AF is not possible during viewfinder shooting.
Group I
Autofocusing with 61 points is possible. All the AF area selection modes
are selectable.
104
: Cross-type AF point. Subject
tracking is superior and high-
precision focusing is achieved.
: AF points sensitive to vertical lines
(top and bottom AF points adjacent
to the center AF point) or horizontal
lines (left and right AF points
adjacent to the center AF point).
Not manually selectable. It works
only when "AF point expansion
(manual selection
: Disabled AF points (not displayed).
: Cross-type AF point. Subject
tracking is superior and high-
precision focusing is achieved.
: AF points sensitive to horizontal lines.
).
)" is selected.