That is, this list is meant as to work as background to the question "does this cut work or not, and why?"
10 Editing "Checks"
by Ted Fisher
At each edit in a work, an editor should consider the following checklist. Not every edit can fulfill each "check," so part of the editor's job is to weigh the importance of each concern and decide what "works."
1. New information
The main concern at any single cut, if one is really going to use the language of moving images, is that the cut give the viewer new information. Otherwise, why cut?
2. 3-D Continuity (Matching)
To create a believable action, a cut must "match." That is, if one cuts from a wide shot of a baseball pitcher to a close up during a pitch, the position of the throwing arm at the cut must "match" between the two shots, even if the shots are filmed months apart.
3. 2-D Continuity (Eye Trace)
No one takes in a frame all at once; the eye moves around the screen. Take this attention into account when making a cut -- one may wish to cut so that the focus of attention is at the same place on the screen, or at a different place, moving the same direction or moving in opposition, depending on the effect desired.
It is generally less jarring to the eye and brain when a cut is made from a well-composed shot to a well-composed shot.
5. Camera Angle
It usually helps if one is cutting to a camera angle that is different enough from the current one so as to be easily understood as a new shot; also it is generally better to cut from a good camera angle to a good camera angle rather than when at a "messier" point in a shot.
Cut in such a way that visuals work with audio and vice versa. Also, maintain sensible audio continuity (e.g., if we cut from a shot inside a speeding car to a close up of a helicopter following it, the audio may need to change with the cut based on where we "are" in relation to the sources of sounds).
We can set up "expectations" in a viewers mind by setting up a rhythm; this can also mean making edits work with the beat of a piece of music or with a certain pace of action.
If a character is in a certain state of mind, editing may reflect their perception, or if the viewer is expected to feel a certain way then editing may amplify that state of mind, sometimes purposefully breaking the "rules" of the six continuity checks. For example, it may make sense to cut a fight scene in a discontinous manner.
Each edit ultimately serves the telling of a story; the idea here is that one may cut on a certain frame or to a certain shot to serve that story rather than the conventional continuity concerns.
Sometimes an edit is motivated by that intangible idea of timing -- the point where it just feels right.