Crossing the Line

In filmmaking, what is the line? Why is crossing it usually a bad thing?

Ever watched a film or video sequence (perhaps one of your own) and it just doesn’t cut together right? It can be painful to watch (especially if it was one of your own). There could be a number of reasons for the edit not working, but in this article we’ll be looking at just one cause – crossing the line.

(Note that there are a lot of animated images in this article, and they may take a while to download.)

What is “The Line”?

The “line” is an invisible or mental line that exists on screen and gives us our sense of direction or perspective for the scene. There are actually two types of line:

The Line of Action:

The line along which our subject/s (actor/s, vehicle/s, etc) are moving; or

The Line of Interest:

The line along which our subject/s are looking (e.g. the line between two characters talking to each other).

The Line of Action

As director, when you are considering your shooting script, you must already be thinking about the editing process. Doing this will not only save you time and film on the shoot, as you won’t shoot anything you don’t really need, but will also minimise the risks that you’ll shoot scenes that won’t cut together.

When planning to shoot a scene where the subject is in motion, imagine that the subject forms an invisible line as they move – this is the line of action. For most shots, it is very important that the camera does not cross the line of action – that is, you should ensure that you film the motion from the same side of the line. Here’s an example:

Top View

In the above top-down view, we see a car travelling south from the top of the image to the bottom. The line of action is represented here by the white arrow. If our first shot is taken from position one, then the car appears to be travelling from left of frame to the right, like so:


If our next shot of the car is taken from position two, then even though the car is now travelling away from us, the apparent direction of the car is still from left to right on the screen – this is because we have not crossed the line of action, like so:


If, however, we had crossed the line of action and shot from position three, then although the car is still in fact travelling in the same direction (south), it appears to be travelling in the opposite direction on screen, like so:


This apparent change in direction makes it nearly impossible for shots from position one and three to cut together, as the shots will jar and confuse the audience, like so:

Cutting 1 and 3 together

Crossing the line this way makes the car appear to change direction on screen, and is best avoided as it marks your project as unplanned and unprofessional. Shots from positions one and two will, however, cut together okay, like so:

Cutting 1 and 2 together

You can see how the car’s direction is maintained. Generally, for scenes like this you will want the car to be travelling in the same basic direction across the screen for each shot. Even if you know that the actual route is quite tortuous and winding, you’ll satisfy your audience and give the character a clearer direction if you stick to this guideline.

But I had to Cross the Line!

If you must cross the line for artistic, plot, or practical reasons, then make sure you have filmed a shot to place in between the cross-over. Perhaps a shot taken from on the line of action, with the subject headed straight towards/away the camera. Better still, a tracking shot that starts on one side of the line and moves to the other side during the shot. Shots like these re-orient your audience to the subject’s new apparent direction.

You may be shooting in an area where you are forced to cross the line due to restrictions on where you can shoot from. If the shot’s background is neutral enough, you can get the subject to move in the opposite direction, which will cancel out the fact that you crossed the line and it will appear to be the correct direction on screen.

Deliberately Crossing the Line

Now that you know how confusing crossing the line can be for your audience, why not use this technique deliberately? There will be times when the disorienting effects of crossing the line can come in handy. Say you have a scene of your actor rushing frantically through a shopping centre looking vainly for a particular store. By continually crossing their line of action you’ll end up with a collection of shots that edited together will show the actor dashing back and forth through the arcade (even if they were actually headed in the same direction), and this will help to convey the character’s disorientation.

Just be careful how often you use this technique – there’s a thin line between conveying to the audience your character’s confusion and just plain confusing your audience – that’s a line you don’t want to cross!

The Line of Interest

So crossing the “line of action” can unnecessarily confuse and disorient your audience, and could mark your work as unprofessional. But you may have heard people talking about avoiding crossing the line even when there is no movement in the shots. In this case, the line they are referring to is probably the “line of interest”.

This “line” is a more subtle and difficult to define line. At it simplest, it refers to the line along which our audience looks back and forth in the scene, usually between two actors, but it could be between more than two actors, or between an actor and a prop or props.

Using the Line of Interest

Lets take, for an example, a shot of two actors talking to each other face to face – let’s call them Grey-Suit and Black-Suit. Here’s a top-down view of our actors talking to each other:

The line of interest will usually extend from one actor’s eyes to the other’s (unless it is an unusually staged or framed scene). So the line of interest would look something like this, represented by the orange line (it’s useful to think of the line extending out behind the actors):

During this scene, our audience will probably be looking back and forth from Grey-Suit to Black-Suit, along the line of interest. Now there are a number of ways you could film such a conversation, but the standard shots you’d think of might include:

1. Main two-shot (a shot which includes profiles of both actors)

2. Reverse angle over Grey-Suit’s right shoulder to Black-Suit

3. Reverse angle over Black-Suit’s left shoulder to Grey-Suit

4. Reverse angle over Black-Suit’s right shoulder to Grey-Suit

Notice that camera positionss one, two, and three are all on the same side of the line of interest. This means that all three shots have a consistent orientation. That is to say, Grey-Suit is always on the left of screen, and Black-Suit is always on the right. Here are the views of cameras one, two and three:

This means that when you inter-cut these shots together during the editing process, the audience will not be confused by the positioning of the characters, as they stay on the same sides of the screen. However, if you were to try to edit in any shots from position four you would probably confuse or annoy your audience as the actors appear to “swap sides” on screen, even though they don’t actually move. Imagine how confusing a conversation between Grey-Suit and Black-Suit would be if we continually cut between camera two and four, like so:

A Thin Line

Unnecessarily crossing the line of interest can actually be more confusing/irritating for an audience than crossing the line of action, even though the latter is often easier to spot. Of course there are many times when crossing the line of interest is the only sensible option, and in many scenes the line of interest can constantly change — even during a relatively simple scene.

During a scene the actor’s may shift their attention from each other to other actors or points of interest, and hence shift the line of interest. As director you must decide where the dominant line of interest is at each moment in the scene, and ensure that you set your shots up so that you aren’t going to have any headaches trying to piece them together in the edit suite.

Plan Ahead

Although only the more experienced audience member can identify every crossed line of action or interest, many times even your average movie-goer or TV watcher will still know that something is “not right” if you cross these lines for no reason — even if they can’t actually name it. The last thing you want is for your audience to “pop out” of your story and notice something strange happening with the continuity of the scene. You want them to be lost in the drama of the scene and not even notice the cuts. Careful planning and attention to details will prevent you from making this frustrating mistake.

Updated: 18 November 1999
Originally written for’s Filmmaking page.