That invisible line: the 180° system
The dominant style of classical Hollywood storytelling is continuity editing, whose goal is to make every cut go unnoticed and serve a clear story. Its foundation is the 180° system: between two subjects in a scene there's an imaginary 'axis of action,' and the camera may only stay on one side of it. That way, as you cut back and forth, the characters' left/right orientation, eyelines, and directions of movement stay consistent (the jargon is 'screen direction').
This axis is usually set first by an establishing shot (often a wide shot), giving the whole scene a predictable 'stage.' Cross the axis (jump the line) and the audience instantly loses track of who's on the left and who's on the right — exactly the consequence, at the editing bench, of the 'line' you learned in Level 1.
Four tools that stitch the cut invisible
Continuity editing relies on a few concrete techniques to make cuts 'invisible': eyeline match (show the direction a character is looking, then cut to what they see); match on action (let one action carry continuously across the cut so the audience watches the action and forgets the edit); shot-reverse-shot (cutting back and forth across the two ends of the axis — the standard for dialogue scenes); and the 30° rule (adjacent shots must change camera angle by at least 30°, or change shot size noticeably, otherwise the cut looks like the picture 'jumps' — a jump cut).
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In continuity editing, the camera may only stay on one side of the 'axis of action' mainly in order to?
答案：Keep the characters' left/right orientation and direction of movement consistent
That's the purpose of the 180° system — preserving screen direction; cross the line and the audience loses their bearings.
'Letting one action carry continuously across the cut, locking the audience's attention on the action rather than the edit' is called?
答案：Match on action
Match on action covers the cut with continuous movement; eyeline match is 'look first, then cut to what's seen,' a jump cut is a hard cut without enough angle change, and an establishing shot opens by laying out the space.
True or false: 'When two adjacent shots change camera angle only slightly (under 30°, with shot size barely changing), the cut looks natural and smooth.'
答案：False
An angle change under 30° (with no clear change in shot size) produces a 'jump cut' — the picture seems to twitch; the 30° rule exists precisely to avoid it.