Stanley Kubrick noted that the editing process is the one phase of production that is truly unique to motion pictures. Every other aspect of filmmaking originated in a different medium than film (photography, art direction, writing, sound recording), but editing is the one process that is unique to film. In Alexender Walker's Stanley Kubrick Directs, Kubrick was quoted as saying, "I love editing. I think I like it more than any other phase of filmmaking. If I wanted to be frivolous, I might say that everything that precedes editing is merely a way of producing film to edit."
In his book, On Film Editing, Edward Dmytryk stipulates seven "rules of cutting" that a good editor should follow:
- "Rule 1. Never make a cut without a positive reason.
- "Rule 2. When undecided about the exact frame to cut on, cut long rather than short" (Dmytryk, 23).
- "Rule 3: Whenever possible cut 'in movement'" (Dmytryk, 27).
- "Rule 4: The 'fresh' is preferable to the 'stale'" (Dmytryk, 37).
- "Rule 5: All scenes should begin and end with continuing action" (Dmytryk, 38).
- "Rule 6: Cut for proper values rather than proper 'matches'" (Dmytryk, 44).
- "Rule 7: Substance first—then form" (Dmytryk, 145).
According to Walter Murch, when it comes to film editing, there are six main criteria for evaluating a cut or deciding where to cut. They are (in order of importance, most important first):
- emotion — Does the cut reflect what the editor believes the audience should be feeling at that moment?
- story — Does the cut advance the story?
- rhythm — Does the cut occur "at a moment that is rhythmically interesting and 'right'" (Murch, 18)?
- eye-trace — Does the cut pay respect to "the location and movement of the audience's focus of interest within the frame" (Murch, 18)?
- two-dimensional place of the screen — Does the cut respect the 180 degree rule?
- three-dimensional space of action — Is the cut true to the physical/spacial relationships within the diegesis?