Principles While Shooting the Action
When a subject moves across the frame, such as a truck moving from the left side of the frame to the right side of the frame, viewers are seeing the truck’s right side. The camera must stay on this side of the line. If the camera operator crosses the line while shooting the truck’s left side, the truck would appear as though it was moving in the opposite direction all of a sudden.
If the camera operator is shooting a shot in which the truck is moving toward or away from the camera, he is shooting on the line, this is not breaking the 180-degree rule. Therefore, shooting on the line is still considered a logical flow of action; however this shot may be distracting if not aesthetically placed accordingly when editing the all shots together.
Breaking the Rules
Now, how do you break the 180-degree rule? Simple! You move the camera, while shooting, across the line. For example, if a Steadicam operator tracks around a subject, he creates a continuous flow of action, therefore he has not broken the 180-degree rule. The operator may stop anywhere, but once stopped, a new line exists.
The main thing you must consider, whether planning your shots while storyboarding or while blocking the set, is to consider the 180-degree rule. It’s simple to follow and once the line is followed, you automatically create a continuous flow of action and a logical sense of direction within your video.