Lighting Basics: Light Colour

Colour Rendering Index Cool White LED Daylight LED Kelvin Light color Light colour Warm White Warm White LED

Colour temperature is a way to talk about the colour characteristics and the appearance of light. Warm lights, which are more red or yellow in colour are those with low colour temperature and kelvin (K) numbers and cool light are higher in kelvin numbers with white or blue colour. We cover some of the basic terms used to discuss the colour of light.

Black Light: A term which refers to a light source emitting light that is mostly near
UV (320 to 400 nm) with very little visible light.

Chromaticity: Is a measure to identify the color quality of a light source as
determined by its dominant wavelength and its purity. It describes the
properties of light related to hue and saturation, but not luminance
(brightness).

Colour Appearance: The resultant color perception that includes the effects of spectrum, background contrast, chromatic adaptation, color constancy,
brightness, size and saturation.

Color Definition: The color of uniformly illuminated objects described using three terms:
Hue: Describes the situation when the appearance of different colors is similar. Lightness: Describes a range of grayness between black and white.
Chroma: Describes the degree of departure from gray of the same lightness and increasing color (e.g. red and redder).

Colour Rendering Index (CRI): CRI is a measurement of a light source’s ability to reproduce the colour of an object to make it appear natural. Both CRI and CCT are terms that are under review now that LED is so prevalent.

Color Shift: The term used when lamps or LEDs change color over the lifespan. Color shift is greatly increased by poor heat dissipation.

Colour Temperature: The color temperature of a white light source is the  temperature in Kelvin of a theoretical black body emitter that most closely matches the spectral characteristics of the lamp.

Cool White: Bright light that is slightly blue in color, generally greater than 4,500K. The Cool White (CW) designation is used specifically for T12 and other fluorescent lamps using halophosphors and having a CRI of 62

Correlated Colour Temperature (CCT): Is a term to describe the relative colour temperature or how the colour of light appears from a lamp on a scale of
warm to cool. The colour temperature is measure on the
kelvin measurement scale (k).

Daylight Lamp: A lamp resembling the color of daylight, typically with a
color temperature of 5500K to 6500K.

Full Spectrum Lighting: A marketing term, typically associated with light sources that are similar to some forms of natural daylight (5000K and above, 90+ CRI),
but sometimes more broadly used for lamps that have a smooth and continuous color spectrum.

Kelvin (K): Is the standard international measure of thermodynamic temperature
(or absolute temperature). The Kelvin scale is named after a Scottish inventor and physicist, William Lord Kelvin who identified the need for an absolute  thermometric scale in the 1800s.

Warm White: Refers to a color temperature around 3000K, providing a yellowish white light.


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