180 degrees rule

The 180 degrees rule is an invisible line that states the camera must be placed on a particular side filming two people in a sequence. If the camera crosses the line suddenly it looks as if the people have changed places to the viewer. A clever way of moving across the invisible line but not breaking the 180 degrees rule is to slowly move the camera round, from there you will only film on that side of the line. 

The image above shows the confusion people can get when the 180 degrees rule is broken. However people purposely break the rule sometimes.

This scene in the shining is good for breaking the 180 degrees rule because it clearly jumps from one side of the room to the other causing the view of the actors to change. This was purposely done to fit with the characters, jumping between the split personality’s splitting the scene, suggesting jack is talking to himself. Although breaking the rule is usually not allowed, in some scenes it holds a hidden message and is a deeper way of connecting with the characters and the movie, such as in The Shining.

The 180-degree rule is either broken for a hidden message like the one in the shining or so they can continue the 180-degree rule at the other side of the room. Although they broke the rule instead of smoothly moving sides in the shot, many carry on the 180-degrees rule after and don’t jump from side to side.

Above is an example of the 180degree rule being used correctly.  All throughout the scene the camera is kept on the left side of the room so we get the sense of the continuity in the scene, most films tend to follow the 180 degree rule as if  its broken can cause disruption to the scene for the viewer as they get confused at where the characters are in the room.