Canon EOS-1DX Af Setting Manualbook page 53

AF point expansion (eight surrounding points)
Focus using one manually selected point assisted by
the surrounding points.
Zone AF
The 61 AF points are divided into nine zones, and
focus is made with the AF points in the selected
zone.
61-point automatic selection AF
All AF points are used with this mode, and the
camera selects and focuses automatically.
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