The 180 Degree Rule

The 180 degree rule is a rule put in place to avoid confusion for the audience of a TV show or film. The rule says that once a scene starts the camera can film anywhere along the 180 degree line however the camera must not cross this 180 degree line. Doing so would cause the characters to appear on the opposite sides which would be a mistake.

This diagram shows the effects of the 180 degree rule. The green side is where the camera is allowed, it shows the guy in the orange on the left and the guy in the blue on the right. In this example the red side is where the camera is not allowed. Having the camera here would have the guy in orange on the right and the guy in blue on the left.