Correlated color temperature

Correlated color temperature (CCT) is the temperature, expressed in kelvins, of a blackbody radiator whose chromaticity is nearest to a light source’s chromaticity. It describes appearance along the warm-to-cool white-light dimension, not the source’s physical temperature.

Blackbody locus: The curve of chromaticities produced by ideal blackbody radiators at different temperatures. CCT assigns a temperature from the point on this curve nearest the source’s chromaticity.
LED lighting: Lighting produced by light-emitting diodes, often engineered to provide specified color and intensity. LED products use CCT to distinguish warm-white, neutral-white, and cool-white output.
Color temperature: A temperature-based description of color associated with thermal radiation or approximate white-light appearance. Unlike true color temperature for a thermal emitter, CCT is an approximation for a source that may not be thermal.
CIE 1931 color space: A color space established by the CIE in 1931 to represent color matching with three tristimulus values. Its chromaticity diagram made it possible to locate source colors against thermal-radiator chromaticities.
Planckian radiator: An ideal thermal radiator whose emitted spectrum depends only on its temperature. Its chromaticities form the reference curve used to define CCT.
Fluorescent lamp: A gas-discharge lamp that produces light when mercury vapor excites a phosphor coating. Its phosphor blend shapes the white appearance summarized by a CCT rating.
Color rendering: The effect of a light source’s spectrum on the perceived colors of illuminated objects. Two sources with the same CCT can render object colors differently because their spectra differ.
ANSI C78.377: An ANSI standard specifying chromaticity requirements for solid-state lighting products. It organizes LED white-light chromaticities into tolerances and nominal CCT categories.
Chromaticity: A representation of color that specifies hue and saturation independently of overall brightness. CCT compares chromaticities rather than the source’s intensity or full spectral output.
White balance: A process that adjusts image color so neutral objects appear neutral under a given illuminant. Camera settings often use color temperature as an approximate control for the illuminant’s white point.

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