Since iOS 11 und macOS 10.13 (High Sierra), Apple's FaceTime video chat app has allowed users to take Live Photos during a video call. If you prefer not to be photographed, you can turn off this feature.
In iOS 11, go to Settings, then FaceTime. From there, toggle off the switch that allows Live Photos to be taken.
In macOS, open the FaceTime app, choose Preferences from the menu bar and deselect "Allow Live Photos to be captured during video calls."
Once the feature has been turned off, Live Photos can't be taken by either participant in the video call – both callers need to enable the feature for it to be useable. — dpa