A boundary changes the movie, not just dialogue.
It changes blocking, camera, rhythm, and cut.
Blocking: change position, distance, movement, or leave the frame.
Camera: reframe, move away, or stop recording when the boundary changes.
Rhythm: wait, slow down, or end the take. Continuity can wait.
Cut: remove an image that no longer fits the boundary.
This is a P4 film-craft reading, not proof of off-camera experience.
If all four stay fixed, nothing changes onscreen.
For the full P4 film essay, tap the Related video.