How to adjust photo mask size on Selfie camera in Android?

Question

Android

During the development process, we encountered a problem and could not yet find an understandable solution.
When creating a Selfie, we show a mask with an oval face that we need to hit. But due to the variety of resolutions, as well as the cameras themselves, a problem arose.
On some devices, to get into the mask, you need to move the phone almost to the outstretched hand, and on some it is almost at the face. Has anyone encountered this problem and how can it be solved?
I would like to achieve that the face mask corresponds to a comfortable arm's length, for example, 30 cm.