Color Temperature

color temperature

The measurement of color expressed in Kelvin (K). The reason this measurement is called a "temperature" is because it was derived from a theoretical object called a "black body radiator." When the radiator is heated, it changes from black to red to yellow to white to blue. The lower the Kelvin rating, the "warmer" or more red and yellow in the light. The higher the rating, the "cooler" or more blue the light. See white balance.

                       Approximate
                       Temperature
  Lighting             In Kelvin

  Candle               1,800 K

  Indoor tungsten      3,000 K

  Indoor fluorescent   4,000 K

  Outdoor sunlight     5,500 K

  Outdoor shade        7,500 K

  North sky           28,000 K

---

color temperature [¦kəl·ər ¦tem·prə·chər]

(statistical mechanics)

Of a solid surface, that temperature of a blackbody from which the radiant energy has essentially the same spectral distribution as that from the surface.

---

color temperature

Of a light source, the absolute temperature at which a blackbody, 1 radiator must be operated to have a chromacity equal to that of the light source.

---

Color Temperature 

(T_c), a parameter that characterizes the variation of the intensity I(λ) of the radiation from some source with wavelength λ in the optical region of the continuous spectrum. The color temperature of a source is equal to the temperature of a blackbody that has the same relative distribution of intensity as the source in the wavelength range in question (seePLANCK’S RADIATION LAW). The color temperature characterizes the relative contribution of radiation of a given color to the radiation of the source; that is, it characterizes the apparent color of the source. The concept of color temperature is widely used in astrophysics, mainly in the study of the spectral energy distribution of stars (seeTEMPERATURE).