Filming & Production
180-degree rule
Also called: crossing the line, axis of action
Draw a line between two people talking. Shoot every angle from one side of it and the person on the left stays on the left in each shot, both keep looking towards each other, and the audience never has to reorient itself. Cross the line and they suddenly appear to face the same way or to have swapped seats, which reads as a mistake even to viewers who could not name the rule. The same logic covers a car crossing frame or a runner in a race. Breaking it on purpose is a recognised device for disorientation, and the clean way to reach the other side is on camera, tracking around the subject in one shot so the audience travels with you.