180 degree rule

The 180 degree rule is essential in keeping the viewer focused and avoiding confusion. Once a scene has been established, the camera must stay on one side of the action.

If two people are facing each other, a line must be drawn. This line usually runs straight down the middle between the two people, like so:

Once this line is in place, the camera can move anywhere providing it stays on the same side of the line once filming has begun. If the camera is switching between two faces during a conversation for example and then suddenly cuts to the other side of the line, then it will appear that both people are facing the same direction instead of looking at each other.