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Common Terms Used in the Lighting Industry

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ANSI (American National Standards Institute)

A private non-profit organization that oversees the development of voluntary instructions and sets performance levels for products, services, processes, and personnel in all industries in the USA.

Average Rated Life

An average rated life (ARL), indicates how long it takes for 50% of light bulbs in a test batch to stop performing. This is also known as their half-life. For instance, if 100 bulbs are tested and have an average rated life of 1000 hours, 50% of the bulbs had died once the test time reached 1000 hours.

Some bulbs might have failed at 40 hours, some after 550 hours, however, half of them stopped performing within 1000 hours. When performing lamp life tests, most manufacturers use three hours for fluorescent lamps and ten hours for HID lamps. Each type of lamp has a specific lifespan that affects its ARL.


A ballast is a tool used in fluorescent lighting systems to control the current to the lamps and provide enough voltage for them to start operating. All HID, fluorescent, and plug-and-play linear LED lights need a ballast to properly operate.

With the help of the right ballasts, the end result can be a cost-effective and energy-efficient lighting solution that gives you more control over the amount of light used in your space. Dimming ballasts are specific units that can adjust the light output of a lighting fixture when combined with a dimmer.

Ballast Factor

A ballast factor is a number that shows how much light a lamp will emit with a specific ballast. This number is typically between 0.70 and 1.20. The value is used to assess different lighting systems depending on light output and power input.

For instance, if you are using a ballast that has a factor of 0.95 to power a light fixture that emits 1000 lumens, that light will emit 950 lumens.

Beam Angle

The beam angle of a lamp is the angle at which the lamp emits light. A conventional bulb has a beam of about 360 degrees, meaning the light it emits surrounds the area and it is not very intense. The wider the beam angle is, the less intense the light will be.

Beam Spread

Beam spread refers to the range of space a light source covers from different distances. As light moves away from its light source, it becomes less intense. To determine beam spread from a certain distance, you can use the following formula:

Angle of Beam x .018 x Distance = Beam Spread

Base Down

Base-down lamps have to be placed in a socket with their base part pointing down. This is a standard requirement for HID lights.

Base Up

Base-up lamps should be placed into a socket with the base part of the lamp upward. This is also a typical requirement for HID lights. For instance, if the socket is in the ceiling, pointing down towards the floor, the lamp will be base up.


Candela is the unit measuring the amount of light a fixture emits in a certain direction.


A negatively charged metal electrode from which current travels in a polarized electrical device.

Center Beam Candlepower (CBCP)

Center Beam Candlepower (CBCP) is a measure of the light intensity at the core of a directional light fixture.

Color Pumping

This development in LED lighting technology saturates and enhances the color spectrum. Lighting that features color pumping boosts the perceived tones of the products displayed under it.

Color Quality Scale (CQS)

CQS is a new parameter for light source quality complimentary to Color Rendering Index that estimates the light quality emitted by a light source established on fifteen color swatches.

Color Rendering Index – CRI

The CRI describes the color rendering index of a light source. The better the light source represents colors, the better the index. Sunlight and incandescent bulbs offer a CRI 100 (best rate). They have a wide spectrum and represent all colors. The CRI of a LED varies between 70 up to 95, the one of a fluorescent tube lies between 60 and 98. It is important to watch the CRI when choosing light sources for a project.

Faces should be illuminated with a high CRI because the skin color should look healthy. Restaurant owners want their dishes to look delicious and all colors of the food should be represented.

Warehouses store goods only and machines or people run through the aisles and check IR code for packing and sending them further. These areas don’t need a good color rendering index as the task involves choosing objects that are not differentiated by their color, a CRI of 70 would be enough. An instrument for measuring the color rendering index is a luminance camera. The software records the spectrum and calculates the color rendering index from that information.

Color Shifting

Color shifting occurs in HID or fluorescent lamps and it involves a great change in the color’s rendering properties and temperature. This happens when the chemical balance gets imbalanced, resulting in the light source emitting a green, pink, purple, or orange hue.

The longer the lamp burns, the higher the chances are that its chemical features will shift and will make the lamp less bright and white than it was at the beginning of its lifespan.

(Correlated) Color Temperature – CCT – K

Each light source is radiating light in a certain light color. The light color is defined by the spectrum of the light source and in comparison to an ideal black body radiator. The black body radiator is emitting visible light when heated up.

The more heated up, the cooler the color temperature. The lower the temperature, the warmer the light color of the radiator. The temperature range of a black body radiator is called a black body line. Due to production processes and material, the color temperature of a light source does not lie on the black body curve.

The light color is then defined as correlated color temperature and is an approximation of the color temperature that is not located at the black body curve but corresponds to lines crossing the black body curve indicated as CCT and measured in Kelvin K as well.

An instrument for measuring the color temperature is a luminance camera. The software is recording the spectrum and calculating the color temperature from that information.

A typical range of color temperatures for products of:

2700K – 3200K: WW Warm White
4000K – 4500K: NW Natural White
5000K – 5500K: DW Day White
6500K – 7500K: CW Cool White


Current is a measure of the electricity flow rate expressed in amperes.

Custom Rebate

Custom lighting rebate programs provide a stimulus for projects that don’t meet the prerequisites of the existing instant or prescriptive rebate programs.

These programs can also provide more profitable incentives on the same applications, however, there are usually many complexities to figure out before getting to those larger incentives.

Cylindric Illuminance

Cylindrical illuminance is measuring vertical illuminance levels of figures, objects, and human faces. Several measurement points are considered. Objects and especially faces are important to illuminate equally without hard shadows.

Delivered Lumens

Delivered lumens is the most accurate measure of the performance of the light after being installed. It shows the exact amount of light delivered on a specific surface, expressed in lumens, taking into consideration barriers such as housing, lenses, as well as any filtering effects present.

DLC Listed

DLC ( Design Lights Consortium) is a rating system which with the help of manufacturer data and testing determines which lighting fixtures are suitable for their designated use. If a lighting product has a certification from this organization, it means it is highly energy-efficient.

Double Ended

Lamps featuring 2 bases on the opposite ends are referred to as double-ended. They are usually meant for series electrical connections, mechanical mounting, and heat dissipation.

Energy Star

A USA government-supported symbol for energy efficiency that provides credible information and classifies a product as energy-efficient to help consumers make well-informed lighting decisions.

ETL Listing

ETL (Electrical Testing Labs) is an electrical safety certification. This certification program is created to test products to the same safety standards as UL listing and ensure a product is safe to be used by customers.


Filament is a tungsten wire in a halogen or incandescent lamp, that when heated electrically radiates in the visible, infrared, and ultraviolet ranges.

Flicker and Stroboscopic Effects

Flicker is disturbing and can lead to physiological effects like headaches. Stroboscopic Effects can result in dangerous situations when changing the visual impression of the movement of rotating machine parts. Lighting systems should be planned to avoid these effects.

Fluorescent Lamp

A fluorescent lamp is a low-weight mercury vapor lamp that emits light with the help of fluorescence. The electric discharge creates ultraviolet energy, which is then absorbed by a phosphor and turned into visible light.

Footcandle (FC)

A measurement unit for light intensity which equals one lumen per square foot.


Glare tires the eye and makes it hard to see clearly in certain spaces. Glare reduces the visual performance and visual comfort of the eye. There are differences in direct and indirect glare.

Direct glare is caused by luminaires or surfaces with too high luminance. If the light sources have no housing for example or if luminaires are mounted wrongly, direct glare can be the result. Indirect glare is caused by specular reflection at mirrors or highly shiny surfaces like monitors, high gloss paper, or wet streets.

It is very important to avoid any type of glare as the visibility is dramatically reduced and the possibility for accidents is exalted. Glare can be measured by the UGR system for indoor applications or as TI rates for outdoor use.

Group Relamp

Replacing all light fixtures at once in a particular area instead of changing them one by one as they burn out.

Halogen Lamps

Halogen lamps are also known as tungsten halogen as they consist of a tungsten filament sealed into a transparent envelope filled with inert and halogen gasses. As opposed to incandescent lamps, these lamps provide whiter and brighter light with richer color, better efficiency, and a longer lifespan.

High-Intensity Discharge (HID)

Gas-discharge arc lamps which generate light by sending an electrical discharge between two electrodes and through a plasma, or ionized gas. They are highly effective and have a long lifespan.

Horizontal Illuminance – Eh – lx

Horizontal Illuminance is describing the illuminance level on horizontal and nearly horizontal spaces like office desks or keyboards.

Illuminance – E – lx

Illuminance is measuring the luminous flux of a light source that reaches a certain surface. It is measured in lm per m² called lux (lx) and appreciated by E. 1lx is measured if 1lm is illuminating equally an area of 1m².

The instrument for measuring the illuminance on a surface is a Luxmeter. Illuminance is not an indicator of brightness! A dark and bright colored room may have the same illuminance level on the floor but the dark one will always appear darker.


A source of electric light that works by incandescence – the emission of light as a result of heating the filament. They come in various different wattages, voltages, and sizes.

Indoor Positioning

Automation that enables customers and employees to locate products or get location-based notifications. It helps retailers to engage customers and use data analytics based on location to determine marketing impact and evaluate store operations.

Instant Start (IS)

A method of starting fluorescent lamps where the voltage applied across the electrodes is twice as high as it is in other methods of starting. This higher voltage is needed as the electrodes are not heated before starting. This method is highly energy efficient as it starts the lamps without flashing.


Kilowatts measure how much energy a device will consume. Converting watts (W) into kilowatts (kW) is very easy: 1 kW is equal to 1,000 W.

Kilowatt Hour

A method to determine the amount of energy used in a certain period of time. Kilowatt hours are determined by multiplying the kW of energy consumption by the hours the lighting has worked.

LED Conversion / LED Retrofit

Replacing inefficient lamps with more efficient LED lighting.

LED Driver

A device that drives the power to one or more LED lights. It is usually built into an LED lamp and it is responsible for various lamp functions such as converting the electrical current to DC, dimming the lamp, and responding to changes in voltage.


Light is visible radiation between 380 nm and 780 nm. Beyond this range, the radiation is not visible to the human eye. It is radiation in infrared, ultraviolet, or radiofrequency. The visible light range is called a spectrum.

The spectrum of a light source contains blue, green, yellow, red, and all the colors in between. The more colors represented in the spectrum, the more colors are visible under the light source. The fewer colors in the spectrum, the poorer the light source’s color reproduction (see also color rendering index CRI and spectrum).

Light Intensity – I – cd

Light intensity is measuring the luminous flux of the light source that is emitted into a certain angle or direction. It is appreciated by I and measured in candela (cd). It is describing the light intensity distribution curve of a luminaire or light bulb (see Light Intensity Distribution Curve LDC). The instrument for measuring light intensity is a Goniometer.

Light Intensity Distribution Curve (LDC)

The Light Intensity Distribution Curve is describing the spatial radiation of a light source or luminaire. It is mostly illustrated as a graphic, showing the curves of the light intensity. The instrument for measuring the light intensity distribution curve is called a Goniometer.

Lighting as a Service (LaaS)

Instead of paying the entire sum for upgrading the lighting in the initial phase of the project, the lighting service provider you choose to work with will install and issue a warranty for your new efficient lighting system at their cost.

After that, you will pay monthly with the money you will save thanks to your new efficient lighting and lower energy bills. This is a great way to benefit from the lighting upgrade and making it cash-flow positive from the beginning.

Lighting Audit

A lighting audit can give you a clearer idea of the energy use of your business operations. An energy auditor inspects your building and takes notes of all your lighting energy uses, interviews managers to locate areas that might need improvement in lighting, and creates a plan to reduce lighting and maintenance costs.

Light Efficiency – lm/W

Light efficiency describes the effectiveness of a light source regarding the electrical energy that is converted into visible light. It shows how much electrical power (W) has been converted into luminous flux (lm).

Some examples:

Incandescent lamps (home application): 12 lm/W
Halogen lamp: 20 lm/W
CFL: 60 lm/W
Fluorescent lamp: 90 lm/W
LED Shop Light: 120-180 lm/W

Light Emitting Diode (LED)

A light-emitting diode is a semiconductor light source that emits light when current passes through it. LEDs are the most commonly used types of semiconductor diodes today.

Light Center Length (LCL)

The distance from a certain reference point on a lamp base to its light center.

Lumen Depreciation

The process of decreasing the total lumen output of a bulb in the course of its lifespan. Every type of lamp has a specific rate at which lumens depreciate and that depends on different factors such as the total hours used, the kind of lighting technology used, the environment, the frequency of turning the fixture on/off, etc.

Lumens (lm)

A measure expressing the amount of visible light from a light source. The higher the lumen rating is, the brighter the light fixture will appear.


Also referred to as a light fitting or a light fixture, a luminaire is a complete electrical unit that contains an electric lamp emitting illumination.

Luminaire Efficiency

The ratio of lumens released by a luminaire to the one emitted by the lamp or lamps used in that specific luminaire.

Luminance – L – cd/m²

Luminance is used for describing brightness. It is measuring the luminous flux from an illuminated or self-lighting surface at the observer’s eye. Luminance L is measured in candela per square meter cd/m². The instrument for measuring luminance is a luminance camera.


Lux (lx) is the unit of illumination and luminous emittance. It is equal to the amount of lumen per square meter (lx=lm/m²). The lux capacity is impacted by the distance between the surface and the source of light.

Magnetic Ballast

An older ballast that gradually controls electricity. This usually creates a hum or a buzz.

Maximum Overall Length

The entire length of a lamp, from the top of the bulb to the bottom part of its base.

Mean Lumens

The light output from a light fixture typically decreases after the lamp has been operated for some time. The mean lumens of a lamp refers to the average light output the light fixture produces over the course of its lifespan.

Metal Halide

This is an HID lamp (High-Intensity Discharge), which means it generates most of its light output from the electric arc within a small discharge tube. This is a very popular option thanks to its high-quality white light and great efficiency.

Nominal Watts

The exact lamp wattage claimed by the manufacturer of the lamp and on the product packaging or any accompanying documents.

Non-Shunted Sockets

Non-shunted sockets have different entry points for the wires, enabling 2 tracks for the electrical current to pass through. The contacts of non-shunted sockets are not connected.

Operating Position

Some light fixtures are designed to be used in specific positions, be that base-up or horizontal.

Planned Lighting Maintenance

A plan designed for having a technician inspect your lighting sources regularly for outages or needed repairs. This strategy is the best way to ensure consistent and efficient lighting within your facility.

Pressed Aluminized Reflector Lamp (PAR)

A lamp whose outer bulb is created from two pressed glass parts fused together. Pressed aluminized reflector lamps can be halogen, incandescent, or HID types.

Point of Sale (POS) Rebate

POS rebates are set around particular product types. They are issued when the exact materials are purchased.


The rate at which energy is taken from an electrical system or dissipated by a load expressed in watts.

Power Factor

The efficiency with which an electrical unit transforms volt amperes to watts. Units that have power factors bigger than .90 are known as “high power factor” units.

Prescriptive Rebate

These programs are not meant to be claimed immediately. The stimulants are paid depending on the parameters related to the sold item.

R9 Color Rendering Value

The R9 color rendering value emits strong and vibrant red tones. Having high R9 quality is very important in retail, restaurant, art gallery, and hospital applications.

Radiation Angle

The radiation angle is the angle of a luminaire in which it emits the light from the light source. It depends on the construction and optical design of the luminaire.

The smaller the radiation angle, the smaller the illuminated surface but the more focused the light on the object. Spots are typical luminaires with small radiation angles to highlight surfaces and objects.

Small radiation angles are used for accent lighting. The bigger the radiation angle, the wider the illuminated surface and the more equally illuminated. High bay luminaires as well as office luminaires can illuminate a wide area equally with a low number of luminaires. Big radiation angles are used for general lighting purposes. The instrument for measuring the radiation angle is the Goniometer.

Rapid Start

Lamps with 2 pins on each end connected to the filament. The ballast heats up the filaments to enable faster starting. RS ballasts can not start lamps safely at cold temperatures.

Single Ended

Lamps that have just one lamp base or point for electrical connection.

Shunted Sockets

Shunted sockets have internally connected electrical contacts. This gives the current a single track to travel from the ballast, through the socket, ending up to the lamp’s pins.


Light is the visible range from 380nm to 780nm, called a spectrum. The more colors are represented in the spectrum, the better the CRI of a light source. Each light source has a different spectral distribution of radiation. Temperature emitters like incandescent lamps have a continuous spectrum.

High as well as low-intensity discharge lamps represent a spectrum according to their filling gas and tube cover slush. An instrument for measuring the spectrum is a luminance camera. The software is recording the different wavelengths and illustrates the spectrum based on that information.

Tube Lighting

Also known as linear or fluorescent lighting, tube lighting technology is dependent upon a chemical reaction inside of a glass tube to emit light. This chemical reaction uses gases and mercury vapor. This interaction ends up producing an invisible UV light which illuminates the phosphor powder coating on the inner part of the glass tube, emitting white “fluorescent” light.

UL Listing

UL is a global safety science company that deals with testing the safety of representative samples of products. If a certain product is UL listed, it means it meets the standard safety requirements.

Vertical Illuminance – Ev– lx

Vertical Illuminance is describing the illuminance level on vertical and nearly vertical areas like signboards or advertisement boards.


Voltage is pressure from an electrical circuit’s power source that pushes current through a conducting loop, resulting in illumination.

Watt (W)

A unit of electrical power or radiant flux that is equal to 1 joule per second. It is used to determine the rate of energy transfer.

Dwayne Kula


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About the Author

Dwayne Kula is President of LED Lighting Supply. On any given day, Dwayne is writing content for the site and helps manage the marketing initiatives that are on-going. He has a Software Engineering degree and still dabbles in writing software for the company as needed. When not working, he enjoys spending time with his family, working out, playing the occasional game of golf and exploring New England.

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