Canon EOS-1DX Instruction Manual page 99

Selectable AF point
You can change the number of manually selectable AF points. With
automatic AF point selection, all 61 AF points will remain active
regardless of this setting.
: 15 points
Fifteen main AF points will be manually selectable.
: 9 points
Nine main AF points will be manually selectable.
With a lens from groups F to H (p.81-83), the number of manually selectable
AF points will be fewer.
Even with settings other than [61 points], AF point expansion (manual
selection
and Zone AF (manual selection of zone) are still possible.
When you press the <S> button, the AF points that are not manually
selectable will not be displayed.
All 61 AF points will be manually
selectable.
Only cross-type AF points will be
manually selectable. The number of
selectable cross-type AF points will differ
depending on the lens.
), AF point expansion (manual selection, surrounding points),
3 Customizing AF Functions
: 61 points
: Only cross-type AF points
99