Skot (symbol: sk) is an old and deprecated measurement unit of
luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls wit ...
, used for self-luminous objects (''dark luminance'').
The term comes from
Greek , meaning "darkness".
Overview
The skot to measure the dark luminance () was introduced in 1940 by the (, LiTG) out of a necessity to describe the luminance of self-luminous objects, which differed so much from that of other objects that it was impractical to describe it using commonly used luminance values.
Conversion factors for so called "scotopic
stilb" () depend on the spectral distribution of the light and were therefore redefined in 1948 by the
International Commission on Illumination
The International Commission on Illumination (usually abbreviated CIE for its French name Commission internationale de l'éclairage) is the international authority on light, illumination, colour, and colour spaces. It was established in 1913 a ...
(, IBK) for a specific color temperature of 2042
K or 2046 K,
the temperature of solidification of
platinum
Platinum is a chemical element; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...
. Before 1948, the definition was based on a temperature of 2360 K
as emitted by a wolfram-vacuum lamp.
At this temperature, 1 sk = 10
−3 asb.
The maximum allowed value is 10 skot to avoid the unit being used up into areas of mixed
scotopic and
photopic vision
Photopic vision is the vision of the eye under well-lit conditions (luminance levels from 10 to 108 cd/m2). In humans and many other animals, photopic vision allows color perception, mediated by cone cells, and a significantly higher vis ...
of the
eye.
Unit conversions
See also
*
Nox (unit) to measure the dark illuminance ()
*
Purkinje effect
*
Photometry (optics)
Photometry is a branch of optics that deals with measuring light
Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectr ...
*
Scotopic lux
*
Scotopic vision
References
Further reading
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* (2 pages)
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* (8 pages)
{{SI light units
Units of luminance
Centimetre–gram–second system of units