Canon EOS-1 DX Mark III Advanced User's Manual page 326

Selecting the AF Area Selection Mode
1.
Press the <
2.
Press the <
Look through the viewfinder and press the <
Each time you press the <
changes.
Note
With [ : Select AF area selec. mode], you can limit the selectable AF area
selection modes to only those you want to use (
If you set [ : AF area selection method] to [
the AF area selection mode by pressing the <
< > dial ( ).
> button ( ).
> button.
326
> button.
> button, the AF area selection mode
).
→Main Dial], you can select
> button, then turning the