Canon EOS-1DX Instruction Manual page 70

S Selecting the AF Area
Select the AF Area Selection Mode
With [24: Select AF area selec. mode], you can limit the selectable
AF area selection modes (p.100).
If you set [24: AF area selection method] to [ →Main Dial], you can
select the AF area selection mode by pressing the <S> button, then
turning the <6> dial (p.101).
70
AF point expansion (Manual
selection, surrounding points)
The manually-selected AF point <S>
and the surrounding AF points <w> are
used to focus.
Zone AF (Manual selection of
zone)
The 61 AF points are divided into nine
zones for focusing.
61-point automatic selection AF
All the AF points are used to focus.
Select the AF area selection
mode.
Press the <S> button.
Look through the viewfinder and
press the <B> button.
Press the <B> button to switch
the AF area selection mode.