Canon EOS R3 Advanced User's Manual page 422

: Flexible Zone AF 1 (default)
With Flexible Zone AF 1, you can freely set the size of the Zone AF frame [
Uses auto selection AF in Zone AF frames to cover a larger area than Expand AF area,
which makes focusing easier than with 1-point AF/Expand AF area and effective for moving
subjects.
By default, a square Zone AF frame is set.
Focusing areas are determined not only based on the nearest subject but also based on a
variety of other conditions such as faces (of people or animals), vehicles, subject motion,
and subject distance.
Pressing the shutter button halfway displays [
: Flexible Zone AF 2
With Flexible Zone AF 2, you can freely set the size of the Zone AF frame [
Uses auto selection AF in Zone AF frames to cover a larger area than Expand AF area,
which makes focusing easier than with 1-point AF/Expand AF area and effective for moving
subjects.
By default, a vertical rectangular Zone AF frame is set.
Focusing areas are determined not only based on the nearest subject but also based on a
variety of other conditions such as faces (of people or animals), vehicles, subject motion,
and subject distance.
Pressing the shutter button halfway displays [
] over AF points in focus.
] over AF points in focus.
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