Canon EOS 5Ds Instruction Manual page 96

AF Area Selection ModesN
AF point expansion (Manual selection, surrounding points)
The manually-selected AF point <S> and surrounding AF points <w>
are used to focus. The AF point expansion is larger than with AF point
expansion (manual selection
wider area. Effective when it is difficult to track a moving subject with
just one AF point.
AI Servo AF and One-Shot AF work in the same way as with AF point
expansion (manual selection
Zone AF (Manual selection of zone)
The AF area is divided into nine focusing zones for focusing. All the AF
points in the selected zone are used for the automatic AF point
selection. It is superior to single-point AF or AF point expansion in
achieving focus, and it is effective for moving subjects.
However, since it is inclined to focus on the nearest subject, focusing on
a specific target may be more difficult than with single-point AF or AF
point expansion.
The AF point(s) achieving focus is displayed as <S>.
96
), so the focusing is executed over a
) mode (p.95).