Lighting ratio in
photography
Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employed i ...
refers to the comparison of
key light
Key or The Key may refer to:
Common meanings
* Key (cryptography), a piece of information that controls the operation of a cryptography algorithm
* Key (lock), device used to control access to places or facilities restricted by a lock
* Key (m ...
(the main source of light from which shadows fall) to the
fill light
Fill may refer to:
* Fill dirt, soil added to an area
** Fill (archaeology), the material that has accumulated or has been deposited into a cut feature such as ditch or pit
** Fill (land), dirt, rock or other material added to level or raise the ...
(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. Since the lighting ratio is the ratio of the light levels on the brightest lit to the least lit parts of the subject, and the brightest lit are lit by both key (K) and fill (F), therefore the lighting ratio is properly (K+F):F although for contrast ratios of 4:1 or more, then K:F is sufficiently accurate.
Light can be measured in
footcandles. A key light of 200 footcandles and a fill light of 100 footcandles have a 3:1 ratio (a ratio of three to one) whereas a keylight of 800 footcandles and a fill light of 200 footcandles has a ratio of 4:1 according to the lighting ratio formula.
The ratio can be determined in relation to
F stops since each increase in f-stop is equal to 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
A light meter is a device used to measure the amount of light. In photography, a light meter (more correctly an exposure meter) is used to determine the proper exposure for a photograph. The meter will include either a digital or analog calcul ...
can automatically calculate the ratio of key plus fill to fill alone.
See also
*
High-key lighting
*
Low-key lighting
Low-key lighting is a style of lighting for photography, film or television. It is a necessary element in creating a chiaroscuro effect. Traditional photographic lighting ( three-point lighting) uses a key light, a fill light and a back light ...
*
Silhouette
A silhouette ( , ) is the image of a person, animal, object or scene represented as a solid shape of a single colour, usually black, with its edges matching the outline of the subject. The interior of a silhouette is featureless, and the silhou ...
References
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Science of photography
Engineering ratios