How to go back again to auto focus while filming the video?

Hi amisch,

Thanks for coming to Apple Support Communities for help today.

It sounds like you may be using an iPhone 13 with Cinematic Mode and it's working as expected. This page of the larger user guide can help explain how it works: Record videos with your iPhone camera.

"Cinematic mode applies a depth-of-field effect that keeps the subject of your video sharp while creating a beautifully blurred foreground and background. iPhone automatically identifies the subject of the video and keeps it in focus throughout the recording; if a new subject is identified, iPhone automatically transitions the point of focus. You can also manually adjust the point of focus while you record, or change it later in the Photos app. Cinematic mode is available on iPhone 13 models.

1. Choose Cinematic mode.
2. On iPhone 13 Pro and iPhone 13 Pro Max, you can tap 1x before recording to zoom in.
3. To adjust the depth-of-field effect, tap , then drag the slider left or right before recording.
4. Tap the Record button or press either volume button to start recording.

• A yellow frame on the screen indicates the person in focus; a gray frame indicates a person is detected, but not in focus. Tap the gray box to change the focus; tap again to lock the focus on that person.
• If there isn’t a person in the video, tap anywhere on the screen to set the focus point.
• Touch and hold the screen to lock the focus at a single distance.

5.Tap the Record button or press either volume button to stop recording.

After you record a video in Cinematic mode, you can remove or change the effect. See Edit Cinematic mode videos on your iPhone."

Have a fantastic day!