The letter

One letter a week, starting soon.

The week's signal, what the makers shipped and what the reviewers found, and the editor's note. No tracking, no ads, nothing else.

We keep your address, your language and the date you joined, nothing else. Every letter has a one-click unsubscribe link that deletes the record.
Cinematography3 min read

LESSON 101

High key and low key

Bright and even, or deep and shadowed.

IN THIS LESSON

  1. The lighting ratio
  2. High key
  3. Low key
  4. Practice: choosing a key

The lighting ratio

The difference between high-key and low-key lighting comes down to the lighting ratio, the strength of the key compared with the fill. It can be measured with a light meter. High-key scenes have a low ratio, approaching 1 to 1, so shadows are faint and the picture is bright and even. Low-key scenes have a high ratio, for example 8 to 1, so large areas fall into shadow and the light picks out only some shapes. Each stop of ratio doubles the difference, so 8 to 1 is three stops between the lit and shaded sides.

High key

High-key lighting began partly for technical reasons, because early film and television did not cope well with strong contrast. It is now used to suggest a cheerful mood and is common in comedy, sitcoms and bright commercials. In the 1950s and 1960s it was often made with three lights per person, left, right and centre, giving uniform light with little modelling. Today soft LED panels do the same job more efficiently. Its advantage is speed, since it suits many set-ups without changes; its weakness is that it adds little drama.

Low key

A low-key set-up may rely on a single key, perhaps with a fill or reflector to keep some control over contrast. It throws parts of the scene into shade and stresses contours, creating chiaroscuro. It tends to make viewers feel uneasy or isolated and is typical of drama, film noir and horror. Classic noirs such as The Big Sleep and Double Indemnity used it heavily; in The Big Sleep, table lamps often light only certain details and leave sharp silhouettes. In both films, light and shadow carry part of the moral story.

Practice: choosing a key

This is working practice. Decide the mood first, then the ratio. For a bright, friendly piece, put a large soft source near the camera and raise the fill until shadows nearly vanish. For a tense or intimate scene, move the key to the side, take the fill away and add black flags to stop light bouncing back. Expose for the lit side of the face and let the shadows go. Check on a waveform that the dark areas still hold a little detail if you want to grade them later.

Try it today

  1. 01Light a face with one lamp and a reflector.
  2. 02Move the reflector close for a near 1:1 ratio and film it.
  3. 03Remove the reflector, add a black card, and film again.
  4. 04Measure or estimate the difference in stops between the two sides.
  5. 05Decide which mood suits a scene you are planning.