Lighting ratio
Encyclopedia
Lighting ratio in photography
refers to the comparison of key light
(the main source of light from which shadows fall) to the fill light
(the light that fills in the shadow areas). The higher the lighting ratio, the higher the contrast of the image; the lower the ratio, the lower the contrast.
Light can be measured in footcandles. A key light of 100 footcandles and a fill light of 100 footcandles have a 1:1 ratio (a ratio of one to one). A keylight of 800 footcandles and a fill light of 200 footcandles has a ratio of 4:1.
The ratio can be determined in relation to F stops since each increase in f-stop is equal double the amount of light: 2 to the power of the difference in f stops is equal to the first factor in the ratio. For example, a difference in two f-stops between key and fill is 2 squared, or 4:1 ratio. A difference in 3 stops is 2 cubed, or an 8:1 ratio. No difference is equal to 2 to the power of 0, for a 1:1 ratio.
In situations such as motion picture lighting sometimes the lighting ratio is described as key plus fill to fill alone. A light meter
can automatically calculate the ratio of key plus fill to fill alone.
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
refers to the comparison of key light
Key light
The key light is the first and usually most important light that a photographer, cinematographer, lighting cameraman, or other scene composer will use in a lighting setup. The purpose of the key light is to highlight the form and dimension of the subject. The key light is not a rigid requirement;...
(the main source of light from which shadows fall) to the fill light
Fill light
In television, film, stage, or photographic lighting, a fill light may be used to reduce the contrast of a scene and provide some illumination for the areas of the image that are in shadow...
(the light that fills in the shadow areas). The higher the lighting ratio, the higher the contrast of the image; the lower the ratio, the lower the contrast.
Light can be measured in footcandles. A key light of 100 footcandles and a fill light of 100 footcandles have a 1:1 ratio (a ratio of one to one). A keylight of 800 footcandles and a fill light of 200 footcandles has a ratio of 4:1.
The ratio can be determined in relation to F stops since each increase in f-stop is equal double the amount of light: 2 to the power of the difference in f stops is equal to the first factor in the ratio. For example, a difference in two f-stops between key and fill is 2 squared, or 4:1 ratio. A difference in 3 stops is 2 cubed, or an 8:1 ratio. No difference is equal to 2 to the power of 0, for a 1:1 ratio.
In situations such as motion picture lighting sometimes the lighting ratio is described as key plus fill to fill alone. A light meter
Light meter
A light meter is a device used to measure the amount of light. In photography, a light meter is often used to determine the proper exposure for a photograph...
can automatically calculate the ratio of key plus fill to fill alone.