30-degree rule

If the camera moves less than 30 degrees, the transition between shots can look like a jump cut—which could jar the audience and take them out of the story.

A similar principle applies to changing the focal length of the lens; a change of less than 20 mm while keeping the same angle of view has a similar perception, and the 30 degree rule is often called the "20 mm/30 degree rule" for this reason.

As Timothy Corrigan and Patricia White suggest in The Film Experience, "The rule aims to emphasize the motivation for the cut by giving a substantially different view of the action.

"[3] Especially in post-continuity editing, there are some cases where jump cuts are used in montage or for aesthetic effect, but generally filmmakers try to avoid them otherwise.

In his book In The Blink of an Eye, editor Walter Murch states: "[We] have difficulty accepting the kind of displacements that are neither subtle nor total: Cutting from a full-figure master shot, for instance, to a slightly tighter shot that frames the actors from the ankles up.