a3: Focus Tracking with Lock-On

G button U A Custom Settings menu

Choose how quickly focus responds if something passes between the subject and the camera when AF‑C is selected for the focus mode.

Blocked Shot AF Response

Choose [5] ([Delayed]) to help maintain focus on your original subject.
Choose [1] ([Quick]) to make it easier to shift focus to objects crossing your field of view.
Regardless of the option selected, blocked shot AF response functions in mode [3] when [3D-tracking] is selected for AF-area mode.
If [Auto-area AF] is selected for AF-area mode, blocked shot AF response will function in mode [3] when [2] or [1] is selected.