Establishing shots are a basic filmmaking technique that have two functions: First, they introduce the spatial relationships of people and places within a scene. Second, establishing shots delineate the axis of action, which is of critical importance in continuity editing.
An establishing shot usually uses a distant framing of the objects, ranging from a long shot (full body) to a medium shot (waist-up). Distant framing is used to show a larger area, at the expense of small details. Shots following the establishing shot usually have a much closer framing, showing spectators much more detail. Establishing shots, like most long shots, are shown on screen for more time than closer shots. The rationale is that spectators need more time to absorb the wide variety of detail in a long shot than they need for close-ups.
A diagram might be useful (apologies for the crude ASCII art):
+------------------------------------+
| |
| |
| |
| |
| O O |
| / \ / \ |
| |A| |B| |
| | | | | |
+------------------------------------+
Shot 1: This is the establishing shot. We see that person A and person B are relatively close together, and if ASCII weren't so limited, the setting of the scene. Note that they appear fairly small on screen, with little close up detail, a result of the distant framing.
+------------------------------------+
| |
| ___ ___ |
| / \ / \ |
| | o o | | |
| @ \| |@ | |
| \__o/ \___/ |
| / \ / \ |
| | A \ / B | |
+------------------------------------+
Shot 2: After the setting has been established, the characters can be shot much closer, showing more detail. This can be important for dialogue scenes, such as the one shown here between person A and B, because their facial expressions might be important to see.
A typical film editing pattern involving an establishing shot is known as establishment/breakdown/reestablishment. An establishing shot is used to introduce a new scene, orienting spectators to the new space. Now that spectators are oriented, the filmmakers can more tightly frame the scene to show more detail, such as in a close-up. Breakdowns commonly involve a shot/reverse-shot pattern, which is often used to shoot dialogue. After the action has passed, a reestablishing shot will reorient the spectators.
A good example of this pattern can be found in Everything2's favorite film, Fight Club. Warning: Very mild spoilers ahead.
Around 23 minutes into the film, the Narrator (Edward Norton) has an amusing conversation with a baggage claim clerk. This scene starts with a shot of a box on a baggage carousel. There is a cut to the true establishing shot, which pans right with the Narrator as he walks from the carousel to the clerk's desk; establishing shots do not have to be static. The establishing shot shows the entire space of the scene, including both of the characters; a long shot was used to show everything, meaning that the characters appear fairly distant. The shot also establishes the axis of action for the scene, which is drawn from the Narrator to the clerk. The breakdown occurs in the conversation, which is edited with a shot/reverse-shot pattern. Typical for this pattern, each character is framed in a medium shot, showing more detail of their faces than the establishing shot did. After their conversation, there is a reestablishing shot, which reminds us of their spatial orientation.
Establishing shots are valuable weapon in the continuity editing arsenal, capable of easily and clearly defining a continuous space in the film.
Notes
David Bordwell and Kristin Thompson. Film Art: An Introduction, Sixth Edition. (New York: McGraw-Hill, 2001).
/msg me with any corrections or comments.