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Lighting Terms


The process of sorting LEDs by performance, color, and Correlated Color Temperature (CCT ) into specific sub-groups to optimize selection process.

Color Temperature:

The description of light color as it relates to the color of an item as it is heated. The radiation and color change as the temperature of an item is increased such as metal that goes from gray to glowing red to orange to white as the temperature increases.

Correlated Color Temperature (CCT):

The absolute color appearance defined by the proximity of the light’s chromaticity coordinated to the blackbody. CCT is used in conjunction with a color tolerance system to specify color consistency.

Color Consistency:

The measurement of how close in color appearance samples of light sources tend to be.

Color Rendering Index (CRI):

An indicator of the accuracy of color rendering an object will experience when lit by a light source.

Efficacy / Luminous Efficacy:

The ratio of light output to the power consumed by the lighting load – lumens divided by watts used (lm/w).


A ratio of the total amount of power consumed by a lighting load compared to total input power to the lighting system.

Heat Sink:

A part of the thermal system of the LED light that pulls or conducts heat away from the LED circuit board and components.

Kelvin (K):

The measurement unit of the color appearance of a light source as compared to color temperature. The higher the number of Kelvins the brighter or higher temperature of the color. For example, a color temperature of 3000K would give of a more yellow light, while a color temperature of 6300K would give off a very blue light.

Light Emitting Diode (LED):

An LED is a semiconductor made from two parts; an P-type, which maintains a positive charge (Holes) and an N-type which maintains a negative charge (electrons). When electric current is applied to the P-N junction the electrons combine with the holes which causes an energy release in the form of a photon which is seen as light.

LED Array :

An Array is a grouping of LEDs that are operated together under the same electrical characteristics. LEDs may be grouped in series, parallel, or some combination of the two.

LED Driver:

Controls the amount of power input to keep the LED from experiencing fluctuations in excess of design parameters and protects the LED’s life.

LED Light Engine:

The assembly of LEDs, circuit board, electrical components, and heat sink. Could also include lens or other mechanical components of a fixture.

Lumen (lm):

The international unit of measure for the total quantity of visible light that is emitted by a source.

Lumen Depreciation:

The percentage of light lost from the initial light Lumen output amount over time.

Lumen Output:

The total amount of light emitted from a lighting source, includes light projected in all directions and distances.

Lux (lx):

The international unit of measure for one lumen per square meter.

Foot candle (fc):

The illuminance cast by one-candela source falling on a surface one foot away.

MacAdam Ellipse:

A MacAdam ellipse is the region on a chromaticity diagram which contains all colors which are distinguishable, to the average human eye, from the color at the center of the ellipse.

Solid State Lighting:

A light source composed of solid state electrical devices such as LEDs or Organic LEDs (OLEDs) as opposed to traditional lighting methods such as electrical filaments, plasmas, or gases.


The unit of electrical power consumed by a lighting fixture to operated it.