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Related to Color temperature: Color Rendering Index, White balance

SI units

the units of measurement generally accepted for all scientific and technical uses; together they make up the International System of Units. (See also metric system.) The abbreviation SI, from the French Système International d'Unités, is used in all languages. There are seven base SI units, defined by specified physical measurements, and two supplementary units. Units are derived for any other physical quantities by multiplication and division of the base and supplementary units. The derived units with special names are shown in the accompanying table.

SI is a coherent system. This means that units are always combined without conversion factors. The derived unit of velocity is the meter per second (m/s); the derived unit of volume is the cubic meter (m3). If you know that pressure is force per unit area, then you know that the SI unit of pressure (the pascal) is the unit of force divided by the unit of area and is therefore equal to 1 newton per square meter.

The metric prefixes can be attached to any unit in order to make a unit of a more convenient size. The symbol for the prefix is attached to the symbol for the unit, e.g., nanometer (nm) = 10−9 m. The units of mass are specified in terms of the gram, e.g., microgram (μg) = 10−9 kg.

Only one prefix is used with a unit; the use of units such as the millimicrometer is no longer acceptable. When a unit is raised to a power, the power applies to the prefix as well, e.g., a cubic millimeter (mm3) = 10−9 m3. When a prefix is used with a ratio unit, it should be in the numerator rather than in the denominator, e.g., kilometers/second (km/s) rather than meters/millisecond (m/ms). Only prefixes denoting powers of 103 are normally used. Hecto-, deka-, deci-, and centi- are usually attached only to the metric system units gram, meter, and liter.

Owing to the force of tradition, one noncoherent unit, the liter, equal to 10−3 m3, or 1 dm3, is generally accepted for use with SI. The internationally accepted abbreviation for liter is the letter l; however, this can be confused with the numeral 1, especially in typescript. For this reason, the capital letter L is also used as a symbol for liter. The lower case letter is generally used with prefixes, e.g., dl, ml, fl. The symbols for all other SI units begin with a capital letter if the unit is named after a person and with a lower case letter otherwise. The name of a unit is never capitalized.


William Thomson, Scottish physicist, 1824-1907. See: kelvin, Kelvin scale.

kel·vin (K),

A unit of thermodynamic temperature equal to 273.16-1 of the thermodynamic temperature of the triple point of water. See: Kelvin scale.
[Lord Kelvin]


/kel·vin/ (K) (kel´vin) the base SI unit of temperature, equal to 1/273.16 of the absolute temperature of the triple point of water.


(K) (kel'vin)
A unit of thermodynamic temperature equal to 1/273.16 of the thermodynamic temperature of the triple point of water.
See also: Kelvin scale
[Lord Kelvin]


device marked at regular intervals, used for measuring;
  • celsius scale; centigrade scale; °C temperature scale with 100 gradations between freezing (0°C) and boiling points (100°C) of pure water, when recorded at sea level

  • fahrenheit scale; °F temperature scale with 180 gradations between freezing (32°F) and boiling points (212°F) of pure water, when recorded at sea level

  • kelvin scale; K temperature scale measured in degrees Celsius from absolute zero; 0K is equivalent to -273.16°C, 0°C equates to 273K, and 100°C equates to 373K

References in periodicals archive ?
These light engines are capable of varying in a continuous manner warm or cool white color temperatures and adjusting hue.
Regardless of whether surgeons are operating on tissue in which the blood flow is heavy or light, they can make the contrast more visible by changing the color temperature.
In addition to color temperature control, provided today only by Color Kinetics, Series 300 DLEs extend the inherent benefits of LEDs, including efficiency, long life, durability, and lack of radiated heat and UV emission, to third-party product designs.
70] lifetime of 120,000 hours; and is available in 2,700K, 3,000K, 3,500K and 4,000K white color temperatures, static colors, and RGB.
IntelliBlend also offers a dynamic monitoring system that continuously calculates the lumen output and color temperature of the light.
DOE published a Gateway report Pedestrian Lighting, concluding that warm color temperature, reduced glare and lower output luminaires "help mitigate glare, improve visual comfort and visibility, and make outdoor spaces more inviting.
In the overall LED market by Correlated Color Temperature (CCT), the 5000K - 6500K segment accounted for the largest market share at over 40% revenue share followed by 2700K - 3000K segment at around half of the revenue share as compared to the 5000K - 6000K segment in 2010.
Lighting Description condition D65 Daylight with UV component, color temperature 6504 K D50 Daylight with UV component, color temperature 5003 K C Daylight with UV component, color temperature 6774 K A Filament lamp, color temperature 2856 K F2 White (fluorescent lamp) F6 White (fluorescent lamp) F7 Color Rendering AAA daylight white (fluorescent lamp) F10 3-band daylight white (fluorescent lamp)
If they get it home and the color temperature is too low, they may hate the light it produces," she says.
In addition, proper color temperature is important: Fluorescent lighting at 3,500 degrees Kelvin is ideal.
can measure tristimulus colorimetrics, chromaticity, color difference, and both color temperature and illuminance of light sources.
The 3,000 K color temperature provides a cool white light for optimum color recognition.