I just watched Stranger than Fiction again because someone I know hadn't seen it yet. So, for the next couple of days I will be sharing a few lessons from this nearly perfect film.
Today's lesson: Crossing the Line.
In filmmaking theory, you set up your camera and establish a scene. This opening places certain characters on particular sides of the screen.
Harold and Ana are now always going to be shown with Harold on the left and Ana on the right. When we go in for close ups, they stay right where they are supposed to be:
Over the Shoulder: Ana
Over the Shoulder: Harold
If you "cross the line" you place the camera on the other side of the room from your establishing shot--thereby shooting from the other side of "the line"--and your characters flip sides, which can be extremely disorienting and annoying to your audience, even if they couldn't tell you what just happened.
Crossing the Line
Now, the editors of 24 assured my class that today's audiences are rather sophisticated and can handle you moving around, assuming you set up the scene properly. And that's mostly true. Even so, crossing the line can really throw a viewer.
But there are several times in Stranger than Fiction where they completely shattered the line. Two instances immediately come to mind: One where Harold is on the bus, and the other where he knocks on a door.
How do they get away with this?
Movement. The characters move from one side of the screen to the other before they cut to the next camera angle. This allows the audience to move with the camera and feel no disquiet from this broken "rule" of film grammar.
So if you find you need to cross the line because of a cramped location or some other reason, be sure to let your actors or camera movement clue the audience in first before you do it.
Your Media Production Mentor