A match on action, a technique used in film editing, is a cut that connects two different views of the same action at the same moment in the movement. By carefully matching the movement across the two shots, filmmakers make it seem that the motion continues uninterrupted. For a real match on action, the action should begin in the first shot and end in the second shot.
It's difficult to visualize this without a real film in front of you, but a diagram may still be useful (sorry about the crude ASCII art). In the situation illustrated below, a person stands up from a sitting position.
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| / \ ^ |
| | o | |
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Shot 1: In this shot, we see the person beginning to get up from a sitting position (albeit, horribly framed). The arrow indicates the person's direction of motion.
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| ___ |
| / \ |
| |o o| |
| | v | ^ |
| \_-_/ | |
| / \ | |
| / \ | |
| | | |
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Shot 2: There is a cut to this shot, which shows the person finishing standing up. The main difference from shot 1 to shot 2 is the position of the camera.
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[1]
Overhead: This overhead diagram illustrates the camera positions for the two shots (the cameras are denoted by the bracketed numbers; the person is the lozenge on the left; the dashed line is the axis of action). When the person begins to stand up, we see the action from the vantage point of camera 1. When the person has stood up quite a bit, we see the action from camera 2.
A much better example of a match on action can be found in Everything2's favorite film, Fight Club. Warning: Very minor spoilers ahead.
Around 36 minutes into the film, the Narrator (Edward Norton) discovers a pile of educational magazines in his and Tyler Durden's (Brad Pitt) house. While the Narrator reads some of the articles aloud--"I am Jack's colon..."--Tyler rides a small bicycle around the house. At the beginning of this scene, there is a match on action right after Tyler asks the Narrator, "Hey, man, what are you reading?" In this match on action, we see two different angles of Tyler riding his bicycle; he comes into the Narrator's room in the first shot, and leaves the room in the second shot.
The match on action is a very valuable technique in continuity editing, a style of film editing that emphasizes clear spatial relationships between objects in a scene. By seeing the same movement beginning and ending in two consecutive, differently framed shots, spectators will easily interpret the space around the action as a continuous whole. Matching on action can help reduce the visual choppiness inherent in cutting.
Continuity filmmakers have become very good at creating matches on action, so it's hard for spectators to appreciate the technical difficulty behind this technique. After all, from the diagram above, it seems simple: Just shoot the same action with multiple cameras and splice together the footage.
However, most films are shot with only one or two cameras. Action films may use more cameras during a complicated stunt to record all the angles in one take, but this is the exception to the rule. Since there is only one camera, filmmakers must shoot multiple takes of the same scene. That is, the actors must repeat their performances for each different camera position.
Furthermore, these takes may be shot days apart. In order to make the transition look seamless, everything in the mise-en-scene must be in the same place during every take. Careful notes must be taken during shooting to avoid continuity errors between takes (in fact, there is a dedicated position for this job, known as the script supervisor, or script girl in the olden days). The actual match on action is created by the editor, who will choose the best takes and cut them together.
It is a testament to the skill of filmmakers that matches on action are rarely noticed by spectators. However, spectators are better able to enjoy the film itself because of that editing transparency.
Notes
David Bordwell and Kristin Thompson. Film Art: An Introduction, Sixth Edition. (New York: McGraw-Hill, 2001).
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