The 180° rule
is a basic film editing
guideline that states that two characters (or other elements) in the same scene should always have the same left/right relationship to each other. If the camera passes over the imaginary axis connecting the two subjects, it is called crossing the line
. The new shot, from the opposite side, is known as a reverse angle
In the example of a dialogue, if Ted is on the left and Bob is on the right, then Ted should be facing right at all times, even when Bob is off the edge of the frame, and Bob should always be facing left. Shifting to the other side of the characters on a cut, so that Bob is now on the left side and Ted is on the right, will disorient the viewer, and break the flow of the scene.
In the example of an action scene, such as a car chase, if a vehicle leaves the right side of the frame in one shot, it should enter from the left side of the frame in the next shot. Leaving from the right and entering from the right will create a similar sense of disorientation as in the dialogue example.
An excellent example of sustained use of the 180 degree rule occurs throughout much of The Big Parade, a drama about World War One directed by King Vidor. In the sequences leading up to the battle scenes, the American forces (arriving from the west) are always shown marching from left to right across the screen, while the German troops (arriving from the east) are always shown marching from right to left. After the battle scenes, when the weary troops are staggering homeward, the Americans are always shown crossing the screen from right to left (moving west) and the Germans from left to right (moving east). The audience's viewpoint is therefore always from a consistent position, in this case southward of the action. Some directors do cross the line for dramatic effect.
Problems caused and solutions
Avoiding crossing the line is a problem that those learning filmcraft can struggle with. In the above example with the car chase, a possible solution is to begin the second cut with the car driving into frame from the "wrong" side. Although this may be wrong in the geographic sense on set, it looks more natural to the viewer. Another possibility is to insert a "buffer shot" of the subject head-on (or from behind) to help the viewer understand the camera movement
In professional productions, the 180° rule is an essential element of a style of film editing called continuity editing
. The rule is not always obeyed. Sometimes a filmmaker will purposely break the line of action in order to create disorientation. Stanley Kubrick
was known to do this. The Wachowski Brothers
and directors Tinto Brass
, Yasujiro Ozu
, Wong Kar-Wai
and Jacques Tati
sometimes ignored this rule also.
The British TV presenters Ant & Dec
extend this continuity to almost all their appearances, with Ant almost always on the left and Dec on the right.
Some filmmakers state that the fictional axis created by this rule can be used to plan the emotional strength of a scene. The closer you place the camera to the axis, the more emotionally involved the audience will be.
In the Japanese animated picture Paprika, two of the main characters discuss crossing the line and demonstrate the disorienting effect of actually performing the action.