In television, film, stage, or photographic lighting, a fill light (often simply fill) may be used to reduce the contrast of a scene and provide some illumination for the areas of the image that are in shadow. A common lighting setup places the fill light on the lens axis, roughly perpendicular to the key light.
The fill light is often softer and, by definition, less intense than the key light. The ratio between light and shadow depends on the desired effect. For example, a fill light that is a small fraction of the power of the key light will produce very high-contrast or low-key lighting, while filling with half or more of the key light power will produce a high key, low-contrast tone.
In cases where the fill light is desired to be darker than what is available without artificial means, a flag or frame may be used to block ambient light and thereby provide what is called negative fill.
An alternative to using a direct light source as a fill is to re-direct or "bounce" the key light towards the subject by using a reflector.
Famous quotes containing the words fill and/or light:
“In so far as one denies what is, one is possessed by what is not, the compulsions, the fantasies, the terrors that flock to fill the void.”
—Ursula K. Le Guin (b. 1929)
“However, the danger in [socially unbalanced relationships] is that the subjection of the woman temporarily calms the man’s jealousy but also renders it more demanding. He ends up making his mistress live like those prisoners on whom light is shone day and night in order for them to be better watched. And things always end in tragedy.”
—Marcel Proust (1871–1922)