A shot is often defined as the basic building block of cinema because filmmakers work by creating a film shot by shot, and then, during editing, they join these shots in sequence to compose the overall film. From this standpoint, a shot corresponds to the length of film that is exposed during production as it is run through the camera from the time the camera is turned on until it is turned off. In this way, the shot forms one unit of a larger scene or sequence that, in turn, is made up of numerous shots. To create a shot, therefore, requires that the location be lit, that the actors be placed within the frame and their movements choreographed, and that other elements of set design and costuming be in place for the duration of the shot.
While this definition of a shot is a fairly standard one in film studies, it is also a rather inelegant one, and it has its share of problems. First, it privileges the shot as it exists during production rather than in a finished film. Few shots ever appear "raw" in a finished film. They are almost always trimmed and massaged during editing, and they are color corrected during the post-production phase and, also during post-production, they have sound married to them. Thus, the notion of a shot being defined as footage exposed from the time a camera is turned on until it is turned off fails to accommodate the ways in which that footage is transformed during the critical post-production phase. A better term for this conventional definition is "take."
A more elegant definition of shot is to regard it simply as the interval between editing transitions. In this sense, a shot comprises the footage punctuated on either side by a cut, a fade, a dissolve, or other transition. This approach is more properly biased toward the organization of audiovisual material in the finished film, and it overcomes the ambiguity that composited shots introduce for the standard definition, which does not conceptually accommodate them very well. Composited shots are those created by combining (compositing) individual elements that have been filmed separately. Special effect shots, for example, are composited in this way: a live actor is filmed against a blue screen; a digital matte painting is created in a computer; a miniature model of the set is constructed. Each (excepting the digital matte) is filmed separately, but all are then layered together in the process of compositing to create the finished shot. That shot is then edited with others to make up the larger scene or sequence. This then, is a weakness with the standard, production-oriented definition of "shot." Understood according to this definition, composited shots are ambiguous because they are composed from other shots that have been combined. Using the alternate definition of shot—the interval between edit points—resolves this ambiguity.