Lighting Terms:

Below you will find a list of lighting terms frequently used in the lighting and energy management industry.

Ambient
The surrounding light level in a given area. It is also the temperature in which a LED light source is expected to operate in. Referring to light, it is the light given off by the Sun, Moon and other light fixtures nearby or even within the same space. operate in. Referring to light, it is the light given off by the Sun, Moon and other light fixtures nearby or even within the same space.

Amperage
The strength of an electrical current measured in amperes. The higher the amperage number, the higher the ability to place more devices on a circuit that will be driven by that amperage. Current (Amps) = Power (Watts) / Voltage (Volts).

Amp
A unit of measurement for electrical current. One volt across a resistance of one ohm will produce a flow of one amp.Lighting Terms Photo

Ballast
A device used with an electric-discharge lamp to obtain the necessary circuit conditions (voltage, current, and wave form) for starting and operating.

Bulb
A bulb is a light bulb, a flashlight bulb, a MR16 or E27 light bulb. A LED light bulb is a finished product that has the LEDs installed, electrical components installed and is ready to be used by the consumer. A LED light bulb is screwed in place, twisted and locked in place, pressed into sockets or contact terminals. A LED is not a bulb, but a bulb can contain LEDs.

Bulb Base
The part of the bulb that is used to set it into place and to make contact with electricity. There are many types and sizes. Most common are E26/27, USA and European standard household size, or medium base as it often is called. The 26 or 27 equates to the diameter measurement in millimeters of the threads of a screw-in bulb base. This type of bulb also includes the PAR 20, PAR 30 and PAR38 types, and a few others. There are MR16 and MR11 type base LED bulbs as well as GU10s.

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.

Color Definition
The color of uniformly illuminated objects described using three terms: Hue – Describes the situation when the appearance of different colors is similar (e.g. matching blues and pinks). 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, redder, pure red).

Color Spectrum
All wavelengths of light, including those perceived by human sight, usually measured in nanometers (nm).

Color Temperature
The description 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 a slightly blue.

Correlated Color Temperature (CCT)
Is the measure used to describe the relative color appearance of a white light source. CCT indicates whether a light source appears more yellow/gold/orange or more blue, in terms of the range of available shades of “white.” CCT is given in kelvins (unit of absolute temperature).

Color Rendering Index (CRI)
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 large range of CRI. LED light CRI values generally range from 60(average) to 90(best). High CRI equates to sharper, crisper, more natural colored pictures while at the same time reducing glare. For example: Cool White CRI = 62.

Color Temperature
A measure of the color of a light source relative to a black body at a particular temperature expressed in degrees Kelvin (K). Incandescent lights have a low color temperature (approximately 2800K) and have a red-yellowish tone; daylight has a high color temperature (approximately 6000K) and appears bluish (the most popular fluorescent light, Cool White, i.e. rated at 4100K). Lamps with color temperatures below 5000K tend to be more yellow/red.

Compact Fluorescent Lamp (CFL)
A CFL is a fluorescent light bulb that has been compressed and sometimes twisted into the size of a standard-issue incandescent light bulb. CFLs are designed to replace an incandescent lamp or bulb and fit into most existing light fixtures formerly used for incandescent bulbs. Modern CFLs are reported to last approximately six times longer and use less power compared to an equivalent incandescent bulb.

Die-Chip
Heart of the LED

Diffuser
On optical element used to mix light rays to improve uniformity.

Driver
Electronics used to power illumination sources. In LED lighting the Driver takes the place of a ballast.

Fixture
A complete lighting unit consisting of a lamp or lamps together with parts designed to distribute the light, position and protect the lamps, and connect the lamps to the power supply.

Full Spectrum
A light bulb or lamp that produces a light spectrum that covers the entire range of visible light (400-700nm) without gaps in its spectral output. White LEDs are inherently a full spectrum light source.

General Illumination
Is a term used to distinguish between lighting that illuminates tasks, spaces, or objects from lighting used in indicator or purely decorative applications. In most cases, general illumination is provided by white light sources, including incandescent, fluorescent, high-intensity discharge sources, and white LEDs. Lighting used for indication or decoration is often monochromatic, as in traffic lights, exit signs, vehicle brake lights, signage, and holiday lights.

Intensity
Is a measure of the time-averaged energy flux or amount of light striking a given area. For bulbs alone this is measured in terms of lumens while for lighting fixtures it is measured in lux (lumens/sq. meter).

Kelvin Color Temperature
A measure of the color of a light source relative to a black body at a particular temperature expressed in degrees Kelvin (K). Incandescent lights have a low color temperature (approximately 2800K) and have a red-yellowish tone; daylight has a high color temperature (approximately 6000K) and appears bluish (the most popular fluorescent light, Cool White, is rated at 4100K). Today, the phosphors used in fluorescent lamps can be blended to provide any desired color temperature in the range from 2800K to 6000K. Lamps with color temperatures below 5000K tend to be more yellow/red, lamps rated between 5000 and 6000K are viewed as white, while lamps above 6000K tend to have a blue cast.

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

LED (short definition)
LED means light emitting diode. LEDs are a solid state device and do not require heating of a filament to create light. Rather, electricity is passed through a chemical compound that is excited and that generates light.

Low-bay
Lighting designed for use when the bottom of the luminaire is less than 20 feet above the floor. Fixtures are usually 22-28″ in diameter in order to spread the light evenly.

Lumen
The unit of luminous flux in the International System (SI), equal to the amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions. Lumens is used to measure light bulbs as standalone light sources. Lighting fixtures are measured by lux output which is lumens per square meter.

Luminaire
A lighting fixture complete with installed lamps and other accessories.

Luminous Efficacy
Is the most commonly used measure of the energy efficiency of a light source. It is stated in lumens per watt (lm/W), indicating the amount of light a light source produces for each watt of electricity consumed.

Lux
Typically used to measure the light intensity produced by a lighting fixture. The higher the lux reading the more light the lighting fixture is producing over a given area. Known as lumens per square meter.

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.

PAR (Parabolic Aluminum Reflector)
Parabolic refers to shape of the base, which is curved to catch and concentrate the light that is produced as well as dissipate any heat produced by the LED. This unit is screwed or plugged into a housing, known as a can, tract light or some other fixture. Par is typically followed by a number that stands for the diameter of the light.

RGB
Stands for red, green, and blue, the three primary colors of light. When the primaries are mixed, the resulting light appears white to the human eye. Mixing the light from red, green, and blue LEDs is one way to produce white light. The other approach is known as phosphor conversion.

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.

Task Lighting/Lamp
An LED light used to specifically light a particular area used for work or reading. Typically found in the form of a desk, floor, or clamp-on lamp, it can be a high powered LED light in any form.

Voltage
The rate at which energy is drawn from a source that produces a flow of electricity (amperage) in a circuit. The difference in electrical charge between two points in a circuit is expressed as volts.

Volts
The International System unit of electric potential and electromotive force, equal to the difference of electric potential between two points on a conducting wire carrying a constant current of one ampere when the power dissipated between the points is one watt.

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

Watts
The unit for measuring electrical power. It defines the rate of energy consumption by an electrical device when it is in operation. The energy cost of operating an electrical device is calculated as its wattage times the hours of use.

White Light
White is defined by Kelvin Temperature or Degrees Kelvin.