During a call in the FaceTime app Open Control Center, tap FaceTime Controls, then tap Portrait.
On open Control Center.
Tap FaceTime Controls, then tap Center Stage to turn it on.
To turn Center Stage off, tap it again.
On some iPad models, again.
Note: While you’re using the rear camera, you can enlarge the image by tapping 1x. Tapping it again returns the image to normal size.
When you’re on a FaceTime call, tap the screen to make the controls appear, then tap Use FaceTime audio settings on iPad