Af Point Expansion - Canon MARK III EOS-1 DS Instruction Manual

3 Custom Function Settings
C.Fn III -8
In the AI Servo AF or One-Shot AF mode with manual AF point selection,
you can increase the number of AF points by using the Assist AF points.
Effective when it is difficult to track a moving subject with just one AF point.
0: Disable
1: Enable (left/right Assist AF points)
The points on the immediate left and right (or top and bottom for a
vertical shot) of the user-selected AF point become active.
2: Enable (surrounding Assist AF points)
The points immediately surrounding the user-selected AF point become
active.
The AF point expansion centers on the selected AF point. Therefore, if a
peripheral AF point is selected, the AF point expansion will be smaller as
shown below.
Assist AF point expanded by 1 point on left and right
Selected AF point
Even when C.Fn III -9-1/2 is set, the expansion will take effect.
C.Fn III -9
0: 19 points
1: Inner 9 points
The user-selectable AF points will be limited to the inner 9 points.
2: Outer 9 points
The user-selectable AF points will be limited to the outer 9 points.
With settings 1 and 2, the selectable AF points and the selection pattern will
be as shown below:
Inner 9 points
170
AF expansion with selected point
Expansion points
Selectable AF point
Assist AF point expanded by 1 point all around
Outer 9 points