Candlelight

A flame is a small warm source that has to sit close to be useful, so the face is lit from near at hand and the room behind it disappears. The scene shrinks to whatever the candle can reach.

It also moves. A flame wanders and the light on a face wanders with it, which keeps a still frame alive without any camera movement at all.

A candle puts out roughly one candela, so the falloff is brutal. Double the distance and you have lost two stops, which is why the wall two metres away records as black.

Colour sits around 1900K, well warmer than a tungsten bulb, so faces go amber and anything blue in the room dies. Several candles grouped together read as one larger softer source while keeping the same colour.

The flame is usually below eye level, so the light comes from underneath. That is part of the look, and it is also why candlelight shades toward the sinister without any other help.

Use it for period interiors, for intimacy, for vigils and for anything that should feel older than electricity.

Avoid it when the audience needs to see the room. Candlelight is a scene about two faces and a table, whatever else was built.

Underlighting is a placement, a source below the face pointing up, and it can be any colour or hardness. Candlelight is a named source that happens to sit low, warm and small.

The tell is falloff and colour. Underlighting can be even across a room. Candlelight cannot reach that far, and it is always warm.

Stanley Kubrick shot the interiors of Barry Lyndon (1975) by candlelight using Zeiss Planar 50mm lenses at f/0.7, made for NASA, because no normal lens could gather enough light. The scenes hold a handful of faces around a table and lose the rest of the room to black.

The light reaches the walls and the effect goes with it. Say the falloff is steep and that the background sits in darkness a short distance behind the subject.

The second failure is a still, even glow. Ask for a gentle flicker and for the source to sit low and close, and ban electric light and even exposure.