Some more on editing…

Editors join shots using a variety of transitions. These serve narrative, dramatic, and emotionally expressive functions and they control the pace and rhythm of the drama.

The most common transitions are the cut (which creates an instantaneous change from one shot to the next), the fade (during which one shot fades completely to black before the next shot fades in from black), and the dissolve (which overlaps the outgoing and incoming shots). Cuts are the most frequent transitions, and typically indicate an uninterrupted flow of narrative information, with no breaks of time or space. Dissolves and fades, on the other hand, may be used to indicate transitions in time and space.

Other optical transitions are available but are used infrequently, such as the iris and the wipe. Editors may also create split screen effects, putting several shots on screen at once by splitting the image into small windows.

Parallel editing and crosscutting are building blocks of narrative, and they enable editors to control time and space. Indeed, this control of time and space is one of the key functions of editing. Editors may use continuity cutting to create a stable and reliable spatial geography onscreen, or they may break continuity to undermine spatial coherence.

With respect to time (i.e., the duration of an event onscreen), editors may expand it by using devices such as slow motion, or by increasing the number of cutaways from a main line of action or increasing the number of shots that are used to cover the action. In either case, the screen time of the event stretches out. During the Odessa massacre scene in Potemkin a mother with a baby carriage is shot in the stomach, and Eisenstein prolongs the moment of her agony by covering the action with numerous shots and then editing among them. The result is that it takes her a very long time to collapse to the ground. Conversely, editors may shrink or contract time by leaving out portions of the action. Jump cuts are an obvious way of doing this.

Editors also help shape the actors' performances, and in doing so they help create the dramatic focus of a scene. An editor's decision to play a line of dialogue with the camera on the speaker will inflect the scene in one direction, whereas the decision to use a reaction shot of another character while the line is spoken will give the moment a different tone and emphasis. If the editor elects to respect the performance, he or she may work with the master shot, allowing the performances to unfold in the relatively unbroken time of unedited shots. On the other hand, if the editor goes to coverage, building a scene with cutaways, inserts, and switches in camera position, then the editing is subtly reworking the performance. Examples include trimming the ends of shots to tighten an actor's apparent psychological reflex or to make him or her seem to jump on another character's line, or dropping inserts into the action to draw out the length of an actor's pause.