LED Lighting Glossary

Ampere (Amp)

The unit for measuring rate of flow of electrical current calculated by the following formula: Current (Amps) = Power (Watts) / Voltage (Volts).

Candela (cd)

The luminous intensity as defined by the international metric standard (SI). The term, retained from the early days of lighting, defines a standard candle of a fixed size and composition as a basis for evaluating the intensity of other light sources.

CIE Chromaticity Diagram

A horseshoe shaped line connecting the chromaticity of the color spectrum.

Color spectrum

All wave lengths perceived by human sight, usually measured in nanometers (nm).

Color temperature

Term used to describe the effect of heating an object until it glows incandescently. The emitted radiation, and apparent color, changes proportional to the temperature; easily envisioned when considering hot metal in a forge that glows red, then orange, and then white as the temperature increases.

Cool White

A description of light with a correlated color temperature between 5000K and 7500K, usually perceived as slightly blue.

CRI or Color Rendering Index

The calculated rendered color of an object. The higher the CRI (based upon a 0-100 scale), the more natural the colors appear. Natural outdoor light has a CRI of 100. Common lighting sources have a wide range of CRI.

Driver

Electronics used to power illumination sources.

Efficacy

(Luminous Efficacy) – The light output of a light source divided by the total electrical power input to that source, expressed in lumens per watt (lm/W).

LED

A Light Emitting Diode (LED) is a solid-state semiconductor device which converts electrical energy directly into light. On its most basic level, the semiconductor is comprised of two regions. The p-region contains positive electrical charges while the n-region contains negative electrical charges. When voltage is applied and current begins to flow, the electrons move across the n region into the p region. The process of an electron moving through the p-n junction releases energy. The dispersion of this energy produces photons with visible wavelengths.

Lumen (lm)

The international (SI) unit of luminous flux or quantity of light and equals the amount of light that is spread over a square foot of surface by one candle power when all parts of the surface are exactly one foot from the light source. For example, a dinner candle provides about 12 lumens. A 60-watt Soft White incandescent lamp provides 840 lumens.

Lumen maintenance

The remaining flux percentage at the rated life of a light source.

Luminaire

A lighting fixture complete with installed lamps and other accessories.

Lux (lx)

The SI (International) unit of luminance, or luminous flux incident on a unit area, frequently defined as one lumen per square meter (lm/m2).

Optic

A device that changes the direction of a ray of visible light, usually by reflection, such as a mirror, or refraction by a lens.

Solid-state lighting

A description of the devices that do not contain moving parts or parts that can break, rupture, shatter, leak or contaminate the environment.

Thermal management

Controlling the operating temperature of the product through design. Examples include heat sinks and improved airflow.

Volt

The term used to describe the electrical potential difference between oppositely charged conductors. For example, there is a 1.5V potential between the top and bottom of a battery.

Warm White

A description of light with a correlated color temperature between 3000K and 3500K, usually perceived as slightly yellow.

Watt

The unit of electrical power used by an electrical device during its operation. Many lamps come with rating in watts to indicate their power consumption. A light source with a higher lumen per watt value is more efficient.