When recording a video using Cinematic mode, the camera identifies where to focus and can automatically change the focus if a new subject is identified. White dots below the frame viewer (or scrubber) show where focus point changes occur. When editing a Cinematic mode video, you can change the focus point manually.
Go to the Photos app on your Mac.
Double-click a Cinematic mode video, then click Edit in the toolbar.
Click Adjust in the toolbar, then drag the Depth slider of the Cinematic adjustment to change the amount of foreground and background blur.