Canon EOS 90D Instruction Manual page 773

C.Fn II-3: AF point auto switching
This sets the switching sensitivity of the AF points as they track the subject
moving dramatically up, down, left, or right.
Applies in [Auto selection AF], [Zone AF], or [Large Zone AF] AF area
selection modes, or with [ u +Tracking] or [Zone AF] AF methods.
0

Standard setting for gradual AF point switching.
+2 / +1

Even if the target subject moves dramatically up, down, left, or right
and moves away from the AF point, the camera switches its focus to
neighboring AF points to continue focusing on the subject. The camera
switches to the AF point deemed most likely to focus on the subject
based on the subject's continual movement, contrast, etc. Setting +2
makes the camera more prone to switch the AF point than with +1.
However, with a wide-angle lens having a wide depth of fi eld or if
the subject is too small in the frame, the camera may focus with an
unintended AF point.
C.Fn II-4: AI Servo 1st image priority
You can set the AF operation characteristics and shutter-release timing for
the fi rst shot with AI Servo AF.
Equal priority

Equal priority is given to focusing and shutter release.
Release priority

Pressing the shutter button takes the picture immediately even if focus
has not been achieved. Useful when you want to give priority to capturing
the decisive moment rather than achieving focus.
Focus priority

Pressing the shutter button does not take the picture until focus is
achieved. Useful when you want to achieve focus before capturing the
image.
Custom Function Setting Items
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