Lighting Terminology Glossary

Standards & Classifications

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.

Class 1 Division 1

Class 1 Division 1, or C1D1, represents the most critical explosion-proof classification defined by the National Electrical Code for hazardous locations. These areas contain explosive atmospheres where concentrations of flammable vapors, gases, or liquids may be present continuously or during normal operating conditions.

Class 1 Division 2

Class 1 Division 2, or C1D2, represents a less critical explosion-proof classification than C1D1, defined by the National Electrical Code for hazardous locations. These areas contain explosive atmospheres where concentrations of flammable vapors, gases, or liquids may be present periodically. This typically occurs in areas where equipment is worked on and the hazardous gases or liquids are released as part of maintenance, but are not released under normal operating conditions.

DLC Listed

DLC (Design Lights Consortium) is a rating system that uses manufacturer data and testing to determine which lighting fixtures are suitable for their designated use. If a lighting product has a certification, it typically qualifies for utility rebate programs.

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 and appliance purchasing 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 the UL listing and ensure that a product is safe to be used by customers.

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.

Light Measurement & Quality

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 failed once the test time reaches 1000 hours. Some bulbs might have failed at 40 hours, and some after 550 hours. However, half of them stopped performing within 1000 hours. When performing lamp life tests, most manufacturers use three hours on/off cycles for fluorescent lamps and ten hours for HID lamps.

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 × 0.018 × Distance = Beam Spread

Candela

Candela is a unit of luminous intensity that measures the amount of light a fixture emits in a certain direction.

Center Beam Candlepower (CBCP)

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

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 an LED typically varies between 70 to 95. For a fluorescent tube, it lies between 60 and 98.

High-CRI lighting is important for applications where color accuracy matters. Faces should be illuminated with a high CRI because skin color should look natural. Restaurant owners want their dishes to look appealing, and all colors of the food should be represented accurately.

Warehouses store goods primarily for identification and movement. These areas don’t require high color rendering for basic operations; a CRI of 70 would typically be sufficient for general warehouse tasks.

Color Quality Scale (CQS)

CQS is a newer parameter for light source quality, complementary to the Color Rendering Index (CRI) that estimates the light quality emitted by a light source based on fifteen color samples.

Correlated Color Temperature – CCT – K

Each light source radiates light in a certain light color. The light color is defined by the spectrum of the light source, in comparison to an ideal black body radiator. The color temperature is measured in Kelvin (K). Common ranges include:

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

Delivered Lumens

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

Footcandle (fc)

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

Illuminance – E – Lx

Illuminance measures the luminous flux of a light source that reaches a certain surface. It is measured in lumens per m² called lux (lx), and represented by E. 1lx is measured if 1lm equally illuminates an area of 1m². The instrument for measuring the illuminance on a surface is a Luxmeter. Note that illuminance is not an indicator of perceived brightness – room surface colors affect brightness perception.

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). Typical examples:

• Incandescent lamps: 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 Intensity – I – CD

Light intensity measures the luminous flux of the light source that is emitted at a certain angle or direction. It is represented by I and measured in candela (cd). It describes the light intensity distribution curve of a luminaire or light bulb. The instrument for measuring light intensity is a Goniometer.

Lumens (lm)

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

Luminance – L – Cd/m²

Luminance is used to describe brightness. It measures 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

Lux (lx) is a 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.

R9 Color Rendering Value

The R9 color rendering value measures how well a light source renders strong and vibrant red tones. Having high R9 quality is very important in retail, restaurant, art gallery, and hospital applications.

Electrical Components & Systems

Ballast

A ballast is a device used in fluorescent lighting systems to control the current to the lamps and provide sufficient voltage for them to start operating. All HID, fluorescent, and plug-and-play linear LED high bays need a ballast to operate properly. With the right ballasts, the result can be a cost-effective and energy-efficient lighting solution. Dimming ballasts are specific units that can adjust the light output 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. 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.

Current

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

LED Driver

A device that regulates 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, enabling dimming capability, and responding to changes in voltage.

Power

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 converts volt-amperes to watts. Units that have power factors larger than 0.90 are known as “high power factor” units.

Voltage

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.

Lamp Types & Technologies

Fluorescent Lamp

A fluorescent lamp is a low-pressure mercury vapor lamp that emits light with the help of fluorescence. An electrical discharge creates ultraviolet energy, which is then absorbed by a phosphor coating and converted into visible light. Note: Contains mercury – proper disposal required per local regulations.

Halogen Lamps

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

High Intensity Discharge (HID)

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

Incandescent

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

Light Emitting Diode (LED)

A light-emitting diode is a semiconductor light source that emits light when a current passes through it. LEDs are among the most commonly used and efficient lighting technologies today.

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 popular option for commercial applications due to its high-quality white light and good efficiency.

Installation & Maintenance

Base Down

Base-down lamps must be installed in a socket with their base part pointing down. This is a standard requirement for many HID lights.

Base Up

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

Group Re-lamp

Replace all light fixtures at once in a particular area instead of changing them one by one as they burn out. This approach can reduce maintenance costs and ensure consistent light levels.

LED Conversion / LED Retrofit

Replacing less efficient lamps with more efficient LED lighting solutions.

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 note of all your lighting energy uses, interviews managers to identify areas that might need improvement in lighting, and creates a plan to reduce lighting and maintenance costs.

Planned Lighting Maintenance

A plan designed to have a qualified technician inspect your lighting sources regularly for outages or needed repairs. This strategy helps ensure consistent and efficient lighting within your facility.

Specialized Applications & Effects

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 Shifting

Color shifting occurs in HID or fluorescent lamps, and it involves a gradual change in the color’s rendering properties and temperature. This happens when the chemical balance becomes 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 properties will shift and make the lamp less bright and white than it was at the beginning of its lifespan.

Flicker and Stroboscopic Effects

Flicker can be disturbing and may 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 designed to minimize these effects.

Glare

Glare causes eye fatigue and makes it difficult to see clearly in certain spaces. Glare reduces visual performance and visual comfort. There are differences between direct and indirect glare. Direct glare is caused by luminaires or surfaces with excessively high luminance. Indirect glare is caused by specular reflection at mirrors or highly reflective surfaces like monitors, glossy paper, or wet streets.

It is important to minimize glare as visibility is dramatically reduced and the possibility of accidents is increased. Glare can be measured by the UGR system for indoor applications or as TI-rated for outdoor use.

Indoor Positioning

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

Financing & Rebates

Custom Rebate

Custom lighting rebate programs provide incentives for projects that don’t meet the requirements of existing instant or prescriptive rebate programs. These programs can also provide more substantial incentives for qualifying applications. However, there are usually additional requirements and complexities to navigate.

Lighting as a Service (LAAS)

Instead of paying the entire sum for upgrading the lighting in the initial phase of a project, the lighting service provider will install and warranty your new, efficient lighting system at their cost. You then pay monthly with the savings from your new efficient lighting and lower energy bills. This can make lighting upgrades cash-flow positive from the beginning.

Point of Sale (POS) Rebate

POS rebates are available for particular product types and are applied when the qualifying materials are purchased.

Prescriptive Rebate

These rebate programs provide predetermined incentive amounts based on specific qualifying equipment parameters.

Technical Specifications

Cathode

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

Cylindric Illuminance

Cylindrical illuminance measures vertical illuminance levels of objects and human faces from multiple measurement points. This measurement is important for ensuring even illumination without harsh shadows.

Double Ended

Lamps featuring 2 bases on opposite ends. They are typically designed for series electrical connections, mechanical mounting, and heat dissipation.

Filament

A filament is a tungsten wire in a halogen or incandescent lamp. When it is heated electrically, it radiates energy in the visible, infrared, and ultraviolet ranges.

Horizontal Illuminance – Eh – Lx

Horizontal Illuminance describes the illuminance level on horizontal and nearly horizontal surfaces like office desks or keyboards.

Instant Start (IS)

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

Kilowatt

Kilowatts measure how much energy a device consumes. Converting watts (W) into kilowatts (kW): 1 kW equals 1,000 W.

Kilowatt Hour

A method to determine the amount of energy used over time. Kilowatt hours are calculated by multiplying the kW of energy consumption by the hours the lighting operates.

Light Center Length (LCL)

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

Light Intensity Distribution Curve (LDC)

The Light Intensity Distribution Curve describes the spatial light distribution of a light source or luminaire. It is typically illustrated in a graph, showing the curves of the light intensity. The instrument for measuring the light intensity distribution curve is called a Goniometer.

Luminaire

Also referred to as a light fitting or a light fixture, a luminaire is a complete electrical unit that contains an electric lamp and components for light distribution, positioning, and protection.

Luminaire Efficiency

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

Lumen Depreciation

The process of decreasing the total lumen output of a bulb during its lifespan. Every type of lamp has a specific rate at which lumens depreciate, depending on factors such as operating hours, lighting technology, environment, and switching frequency.

Magnetic Ballast

An older type of ballast that uses magnetic components to regulate electricity. This type typically creates an audible hum or buzz during operation.

Maximum Overall Length

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

Mean Lumens

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

Nominal Watts

The specified lamp wattage is claimed by the manufacturer and indicated on product packaging or accompanying documentation.

Non-shunted Sockets

Non-shunted sockets have separate entry points for the wires, enabling independent electrical paths. The contacts of non-shunted sockets are not internally connected.

Operating Position

Some light fixtures are designed to operate in specific positions, such as base-up, base-down, or horizontal orientations, for optimal performance.

Pressed Aluminized Reflector Lamp (PAR)

A lamp whose outer bulb is created from two pressed glass parts that are fused. PAR lamps can be halogen, incandescent, or HID types.

Radiation Angle

The radiation angle is the angle through which a luminaire emits light from the light source. It depends on the construction and optical design of the luminaire. Smaller radiation angles create focused light for accent lighting, while larger radiation angles provide wider, more even illumination for general lighting applications.

Rapid Start

Lamps with 2 pins on each end are connected to the filament. A ballast preheats the filaments to enable faster starting. RS ballasts may not start lamps reliably at very cold temperatures.

Shunted Sockets

Shunted sockets have internally connected electrical contacts. This provides a single electrical path from the ballast, through the socket, to the lamp’s pins.

Single Ended

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

Spectrum

Light is the visible electromagnetic radiation range from approximately 380nm to 780nm, called the visible spectrum. The more wavelengths represented in the spectrum, the better the color rendering ability of a light source. Each light source has a different spectral power distribution.

Tube Lighting

Also known as linear or fluorescent lighting, this technology depends upon electrical discharge through gases and mercury vapor inside a glass tube. This process produces UV light that excites the phosphor powder coating on the inner tube surface, emitting visible “fluorescent” light.

Vertical Illuminance – Ev – Lx

Vertical Illuminance describes the illuminance level on vertical and nearly vertical surfaces like signboards or advertising displays.

Safety Note: Electrical lighting installations should be performed by qualified professionals in accordance with local electrical codes and regulations. Always consult with certified electricians for installation, maintenance, and safety requirements.