Canon EOS-1DX Instruction Manual page 103

Initial AF point,
You can set the AI Servo AF's starting AF point for when the AF area
selection mode is set to Auto selection: 61 pt AF.
: Manual
If you switch from Manual select.:Spot AF, Manual selection:1 pt AF,
Expand AF area:
pt AF, AI Servo AF will start with the AF point that was manually
selected before the setting was switched. Effective if you want AI Servo
AF to start with the AF point which was selected before the AF area
selection mode was switched to Auto selection: 61 pt AF.
Under [85: Custom Controls], if [AF area selection mode] is set to
Auto selection: 61 pt AF on the [Switch to registered AF func.]
(p.350), or [Register/recall shooting func] (p.355) setting screen and
you use Manual select.:Spot AF, Manual selection:1 pt AF, or Expand
AF area: , you can press the function-assigned button to switch from
the previous AF point to AI Servo AF that uses Auto selection: 61 pt AF.
When [Manual
which has the manually-selected AF point. This will apply even when the AF
area selection mode is switched to Zone AF (manual selection of zone).
AI Servo AF
: Initial
AI Servo AF will start with the manually-
selected AF point when the AF mode is
set to AI Servo AF and the AF area
selection mode is set to Auto selection:
61 pt AF.
AF pt
, or Expand AF area:Surround to Auto selection: 61
AF pt] is set, AI Servo AF will start with the zone
3 Customizing AF Functions
AF pt selected
103