There is a rule in cinema called the 180 degree rule. This rule refers to that once the spacial relationship has been established in the scene, no close-up will cross the imaginary line drawn between the two actors until a new line has been established in the shot. The main reason for this rule is to keep and establish continuity in the scene.

The first step in figuring out the rule is to establish the line of action. This imaginary straight line drawn between a subject and the person or item they are interacting with and also is along a path that the subject is moving on. Then establishing the shot will allow the view basic spacial awareness of the scene and determines the screen direction of the actors or action.

I found this very useful because I have never made my own film, but if I would have without this information, it would look sloppy and confusing. It is an interesting tool to know because watching films now I will be very conscious of the rule and it also might help establish from unconventional and mainstream films.

This video that I found is a little goofy, but it is actually very informative with examples and explaining exactly what the 180 degree rule is in film. A very interesting part of this is also that fact that Russel Hasenauer, the narrator, says that there are also plenty of reasons to break the rule, in dramatic fashion or for an effect of disorientation.

This is a great example of how the rule can be broken for the benefit of the film, or in this case TV show.

-Betsy Thyfault