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LED Lighting Glossary

LED Lighting Glossary2020-04-03T07:26:52+00:00

A B C D E F G H I J K L

A

AC: This is an acronym for alternate lighting. This refers to a source where the voltage polarity changes several times in a second, in the frequency of 50Hz-60 Hz. Alternating current is mostly used in commercial spaces and homes. It is referred to as the line voltage. In the US, the line voltage is usually 90V – 220V. However, it is much higher in Europe.

Accent Lighting: A term for directional lighting. As the name suggests, this type of lighting is mainly used to focus on a particular object during the product display in the retail applications and galleries.

Active Cooling: A process of cooling where power is used to cool components. For instance, a fan is used to exhaust heat from components.

ALA: It is an abbreviation for the American Lighting Association, which focuses on the residential lighting trends. This trade organization has members from the US, Canada, and the Caribbean nations. ALA offers membership to event organizers, designers, as well as manufacturers from the said states. The organization member showrooms boast of providing the highest quality indoor and outdoor lighting solutions for new or retrofit projects.

Ambient Lighting: The lighting that is widely used to improve the visibility of any built or well-designed environment. Ambient lighting may include natural and artificial lighting. However, this term is not suited for any accent or task lighting used in various open areas and industries.

Ampere or Amp: This is the measurement for the electric current in the International System of Units. A current of one ampere is defined as one coulomb of charge in a second. It is expressed as 1 A= 1 C/s. During the lighting installations, the protection and wiring is mainly calculated on the basis of the ampere needed for the operation of the circuits. Along with the ampere, the voltage of these circuits is also taken into the account.

Amp Calculations: As the name suggests, these are the calculations performed to determine the current required by a circuit comprising multiple lighting fixtures or a single lighting fixture. Once the current is analyzed, then it becomes easy to identify the right wiring needed for the lighting circuit, and other protection devices used in the circuit.

Angle of Light: This is the angle that is formed between the viewing direction, as well as a light source. For instance, the light angle will be high, if you are looking at it from the distance, however, it becomes zero, when you look at it from a nearby angle.

ANSI: It is an abbreviation for the American National Standards Institute, which develops standards and voluntary guidelines for electrical industries.

ANSI Ballast: This term refers to a ballast that is ANSI compliant.

Application: It refers to the intended use of light in a particular environment. For instance, retail, residential, healthcare, hospitality, and high bay lighting are some examples of LED applications.

Arc Tube: A sealed ceramic or quartz tube where the light is produced through the electric discharge (arc).

Arc Lamp: A light source that produces an arc between two electrodes. The light arc stimulates a gas, which produces a glow.

Architectural Lighting: This refers to the decorative lighting used to light a building. Architectural lighting may also serve as ambient lighting.

Argon: It is one of the noble gases. Argon is used in the bulbs of traditional incandescent lights. The gas helps prevent oxidation of filaments made of metals. Argon gas is also used in gas discharge lamps that emit blue or the violet light on mixing with mercury.

ASHRAE: This stands for the American Society of Heating, Refrigerating, and Air-Conditioning Engineers.

Average Rated Life: Depicted in hours, the average rated life of a lamp is calculated through various lamp life testing procedures. This depicts the time of failure of a large group of lamps, when they are operated at nominal current and lamp voltage. Typically, manufacturers employ 10 hours and 3 hours per start for HID and fluorescent lamps while performing the tests on them. Every lamp has a mortality curve that provides information on its life expectancy.

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B

Backlight: In some applications, outdoor fixtures may emit light in the opposite direction than intended, and this is known as a backlight. This backlight may produce undesirable results. For instance, the pole lamps fitted in a parking lot may produce backlight that may fall on apartments or homes nearby. This may sometimes be discomforting for residents. Backlights are not the same as backlighting.

Backlighting: An object is illuminated from its back to create a halo-like effect. This lighting creates a glow on the edges of the object. Backlighting is usually done to highlight the artworks in museums and art galleries.

Baffle: It is a translucent or opaque component that blocks the sight of a lighting source.  

Ballast: It is an integral component of an HID and fluorescent lighting fixtures. This component is designed to control the electric current and voltage required for the lamp during the operation or ignition phase. A ballast helps prevent premature heating or overheating. Dimming ballasts are used with dimmer to manage the output in various settings. Ballasts can be electronic or magnetic depending on their construction. The lighting ballasts used in the US are ANSI compliant.

Ballast Efficiency Factor: This is a term for ballast factor divided by power in watts. This factor is used to compare the efficiency of a ballast.

Ballast Factor (BF): A value that defines the effect of the ballast on a lamp’s lighting output. This value is taken in reference to the ANSI ballast factor. The light operated on a ballast is compared to the lamp operated on a reference ballast adhering to ANSI. The lamp is operated on the reference ballast in nominal value of power rating specified by ANSI. The reference value of BF is 1.0. However, in the case of fluorescent lamps, it may differ up to a great extent.

Base: It is a part of the lamp that is connected to the lighting fixture to produce a strong connection. This part provides both electric power as well as support to the electric lamp. The bases of LED lights used in residential applications are fixed using multiple pins or screws.  

Base Down: When the lamp is inserted in a socket with its base pointing downwards, it is called base down position. This position is common to the HID lighting.

Base Temperature: It is the maximum allowable temperature for a lamp base to operate. It is one of the important considerations when designing a lamp.

Base Up: The lamp is inserted in a socket with its base pointing upwards, and this is called a base up position. This is another common specification for the HID lighting.

Bayonet: It is one of the important types of base that is connected to socket utilizing keyways. This lamp base is unlike other bases, which use threads for connection.  

Beam Angle: A downward cone of light produced by the lighting fixture possessing a reflector. It is often measured between the two directions – where high light intensity is produced by the lamp and in the direction, where the light intensity is 50% lesser. This angle is measured respective to the downward direction of light. The lamp having a large angle will spread light in a wider cone.

Beam Spread: It is the range of the surface illuminated. The beam spread is often expressed in the units of distance. It is calculated by multiplying the beam angle by 0.18. The result is then multiplied by the distance of the surface and the light source. This beam spread is not the same as the field spread, which refers to the outermost area illuminated by the light source.

Bi-Pin Base: Any light base that uses two pins is known as bi-pin base. 

Binning: LEDs are grouped according to specifications such as their light output, voltage, and color. This grouping is called binning.

Bollard: A type of outdoor lighting fixture, which features a short and broad post having a lamp on its top. The bollards are used for both purposes – decoration and outdoor lighting.

Brightness: When light is reflected in a specific direction it is called brightness.

Bug Rating: It is an acronym for backlight, uplight, and glare. Developed by the International Dark-Sky Association (IDA) and the Illuminating Engineering Society (IES), this term refers to the amount of light produced by fixtures in those directions, where they are not appreciated. Backlight refers to the light that is produced behind the luminaire. Uplight is the light that is directed upwards, where it may not be required. Glare is an undesirable visual impact produced by light. The effects of lighting are indicated in BUG rating on the scale of 0 to 5. 0 is the minimal bug rating, whereas 5 is the highest bug rating. The BUG rating of B0 U0 G0 is considered the best, whereas the rating of B5 U5 G5 is the worst.

Bulb: The glass casing that contains a light source. The glass casing produces light when electricity passes through the bulb.

Burn Position: Every lamp is designed for some operating position, which is known as the burn position. For instance, a few types of lamps can only perform when they are placed in a base-up position. If the lamp is placed in a position for which it is not designed then its performance may reduce over time, and it may even face short-term failure.

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C

Can: This is a name for the housing of a downlight that is recessed.

Candela: Abbreviated as Cd, this is the measurement of luminous intensity. It is a term used to denote the amount of light produced in a specific direction. This is not the same as lumen (lm), which is a measurement unit for the total lighting produced by a luminaire. The lumen is not confined to any particular direction; however, candela is confined to one direction. A wax candle produces luminous intensity of 1 Candela.

Canopy: It is a lighting fixture used to cover the wiring connections and the outlet box from environmental elements. Many times, these canopies have decorative elements on them.

Cave Effect: This an effect produced when the lighting fixtures are directed downwards. There is no light reflected upwards towards the upper wall or the ceiling. Although this effect may be purposely created, it is not considered to be desirable for regular use because they lend a gloomy effect to the room.

Cathode: This is a negatively charged electrode, which allows electrons to enter into the electrical device.

CBMA: This is an abbreviation for Certified Ballast Manufacturers Association. This is an organization that issues certifications for ANSI standards. The ballasts that are provided with CBM seal have the minimum ballast factor of 0.85.

Ceiling Cavity: This is a portion of the room that lies above the luminaire or the lighting fixture.

Center Beam Candlepower (CBCP): It is the light intensity measured at the center of a light beam produced by a reflector lamp. This measurement is depicted in candelas.

CIE: This is the International Lighting Commission, which is named as Commission internationale de l’éclairage in French. This organization develops standards for the lighting industry across the globe.

Chandelier: A type of decorative lighting structure hung on the ceiling. This decorative piece is easily visible owing to its branch like parts that host several lights. Sometimes, these chandeliers can host candles, too.

Chromaticity: This is a measure of the quality of color as mentioned in the International Commission on Illumination (CIE) color chart published in 1931. It offers an information on X/Y coordinates of red, green, and blue (RGB). The RGB combinations produce different shades of white, whereas the color of white LEDs is shown through a narrow strip found at the center of the CIE chart.

Circline Lamp: As the name suggests, it is a type of circular fluorescent lamp. In such lamps, the fluorescent tube is circular, and the ballast is positioned in the middle of the lamp.

Circuit Breaker: It is an important type of an electric protection device. The circuit breaker is mostly placed in a distribution board. It is connected to every lighting circuit on the board. It is designed to interrupt the current whenever fault or overload is detected.

Coefficient of Utilization (CU): This is described as the efficiency of a lamp in transferring luminous energy to the working plane in an area. In reality, only a fraction of luminous output hits the working plane. The CU is influenced by several factors such as colors of the room, geometry of the room, and so on.  The Coefficient of Utilization is basically a measure without any unit.

Cold Cathode Fluorescent Lamp (CCFL): A type of fluorescent lamp that utilizes high voltage to emit electrons. However, other traditional, conventional fluorescent lamps produce electrons when their electrodes are heated. In comparison, CCFL lamps are less efficient than traditional fluorescent lamps. However, they offer a service of more than 60,000 hours, which makes them comparable to LED lighting in many applications.

Cones: They are the photoreceptor cells found in the retina of human eye. These cells function well in bright light.

Color Definition: The objects that are uniformly illuminated are distinguished using three terms Lightness, Hue, and Chroma. Lightness is a term that describes a grayness range between white and black. Hue is the term used to define the situation when different colors appear similar. Chroma describes the degree of departure of the color from its original. This term is most commonly used to describe the increasing brightness of the color. For instance, green and greener.

Color Appearance: This is the perception of a color. Color appearance is always a combination of different factors such as background contrast, the effects of spectrum, chromatic adaptation, brightness, color constancy, saturation, and size.

Color Consistency: This term shows how close the color appears in random samples of a source or lamp.

Color Matching: When the color appears same as the given color, it is called color matching. This method is often used for evaluating the light’s ability to render the colors properly.

Color Quality Scale (CQS): It is an alternative to CRI and provides a gauge of the light quality produced by any light source. CQS is always considered in accordance with the 15 light swatches.

Color Rendering Index (CRI): It is a metric that defines how perfectly a light source can highlight the true colors of spaces and objects in comparison with a natural light source. CRI is often measured on the scale of 0 to 100 percent. A lighting source having CRI above 80 is commonly considered for most industrial applications. A light source having CRI above 90 assures better color rendering, and is considered for color critical applications such as art restoration. A standard LED lamp have CRI of 83% and halogen bulbs or incandescent bulbs have high CRI score of 100%. This CRI is independent of the color temperature.

Color Shift: It is the change in a correlated color temperature of the lamp. Color shift is measured at 40% of the lamp’s life, and is measured in kelvin (K).

Color Stability: This is the ability of the light source to maintain its color appearance as well as color rendering properties during its lifetime. It has been noticed that some discharge light sources tend to shift over their lifetime.

Color Vector Graphic: This helps understand the saturated and unsaturated colors. Also, users will get to know if there is any shift of hue in any part of 16 color bins.

Continuous Dimming: A dimming method where the output of light is adjusted at a level between 100% output and OFF. This dimming is usually performed in incremental steps.

Compact Fluorescent Lamp (CFL): It is a fluorescent lamp featuring a compact-sized tube. As the name suggests, the tube in these lamps is bent to meet the space requirements. These lamps have screw bases and in-built ballast, which makes it easier for users to replace halogen bulbs and incandescent bulbs directly and effortlessly.

Cool White: A light source that has color temperature above 4500 K. These light sources do not have a characteristic hue of warm white LED lamps or incandescent bulbs.

Cornice Lighting: When the fluorescent light is positioned in a soffit of the junction of wall and ceiling, it is called cornice lighting.

Correlated Color Temperature (CCT): A term that indicates the numerical value of a color. CCT is often measured in Kelvins. Warm and red colors have low color temperatures while cool colors have high temperatures. The light sources having warm or tinge of yellow huge create relaxing environments and they have a CCT of 2700K. However, the light sources having 4000K produce a neutral tone and they strike a perfect balance between concentration and relaxation. The light sources having 6500 K may produce an energizing effect.

Cove Lighting: A type of decorative lighting, which is used to emphasize the features of a ceiling or highlight walls. In cove lighting, the light is usually directed onto the ceiling to create a desired effect.

Crest Factor: A term for the ratio of maximum current utilized by the lamp to average operating current of the lamp. A lamp will have a low service life if its crest factor is high, and vice-versa.

Cutoff Angle: An angle beyond it becomes difficult to see a light source with naked eyes. This angle is often measured from the direction that lies below the lamp.

Cutoff Luminaire: The Illuminating Engineering Society of North America (IESNA) is an industry-backed, non-profit society, which works with the aim of promoting good lighting practices. It has defined several outdoor illuminaire cutoff classifications, which described the light distribution metrics in detail. There are four classifications prescribed by IESNA, which are identified as Full cutoff, Cutoff, Semicutoff, and Noncutoff. These classifications are identified into two relevant zones w.r.t to Nadir. One zone covers angles above 80° above nadir and the second zone covers angle above an angle of 90° above nadir. In a cutoff luminaire, the luminous intensity measured in candelas above the angle of 90°nadir will not exceed 2.5% of the luminous flux of the lamp. The luminous intensity above an angle of 80° above nadir will not exceed 10% of the luminous flux of the lamp.

Custom Rebate: These lighting rebate programs specially address the projects that is not covered any existing or prescriptive rebate programs. Custom rebate programs may provide several lucrative incentives for the applications. However, they involve several variables, and beneficiaries have to sort through several complexities to avail these rebates.

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D

DALI: This stands for Digitally Addressable Lighting Interface, which is a communication protocol for lighting automation.

Daylight Harvesting: This is an architectural strategy of lighting design, which helps maximize the use of natural light in indoor areas to reduce energy consumption during the day. Such indoor spaces are natural, comfortable, and appealing.

Daylight Lamp: This lamp has a CCT value between 5500K and 6500K, which is equivalent to daylight; however, this is not actual daylight. It is artificial lighting, which is the closest possible replication or simulation of natural light in terms of color and luminosity.

DC: This stands for direct current wherein the current flow is unidirectional.

Delivered Lumens: Light thrown on a surface in a particular area is expressed in lumens per unit area. One lumen per square foot equals one-foot candle, while one lumen per square meter equals one lux.

Desk Lamp: These are compact-sized portable lamps meant to be kept on desks and writing tables 

Die: This is a small portion of a semiconductor material cut from a larger silicon wafer, with the help of a die cutting machine.

Diffused Light: This is used to produce soft light for a soothing ambience in rooms, and helps avoid the intensity and glare of direct light as well as shadows. The light source is placed inside a lamp shade or ceiling.  It is produced by an extended surface, and scattered in multiple directions.

Diffuser: This is a piece of glass or acrylic used in diffused light covers or lamp shades. It helps scatter the light in a uniform manner without the original glare and intensity.

Dimmable: This term is associated with lamps and fixtures wherein their luminosity can be controlled and modified with the help of a dimmer device.

Dimmer: This is a regulating device for certain lights to control their light output. Dimmers can be used to make indoor environments more customizable and personal, and help reduce energy consumption.

Diode: It is a device with two terminals used as a one-way switch, which facilitates the flow of electric current in one direction and blocks the same in the opposite direction. The former is known as forward-biased condition and the latter as reverse-biased condition.

Directional: This indicates the flow or occurrence of something in one direction. In terms of LEDs, you can focus light only in the required area for an increased efficiency.

Direct Lighting: It is a type of lighting where more than 90% of the light from the source is focused on the area required to be illuminated.

Direct glare: This is the glare which is an output of the high intensity of lights or luminance. This may also happen due to insufficiently shielded light sources in the field of view or light reflected in certain areas.

Directional lighting: Some luminaires or chandeliers have focused lights illuminating differently or rather in specific directions.

Directed Light: It is the light produced by point surfaces for a focused output that highlights the edges and shadows. It is difficult to look at this light source directly as it is intense and glaring.

Disability glare: Glare often reduces visibility and comfort of the viewer, and hence this term is used to describe the decreased visual performance of the luminaire.

Discharge lamp: This is a light-producing device that depends on an electric arc, rather than filament, to create illumination.

DLC Listed: DLC is a rating system that identifies the most acceptable lighting products based on their intended use. They do this through the data gathered from manufacturers and suppliers.

DMX512: This is a standard for digital communication networks used for theatrical or stage lighting. A single DMX universe has 512 addressable channels.

Downlight: This is a compact lighting fixture designed to provide light in the downward direction. It can be recessed, surface-mounted or pendant.

Double Ended: These lamps have two bases opposite to one another. These are mostly designed for series electrical connections, mechanical mounting, and heat dissipation.

Driver: It is an LED power supply device, which offers a constant level of current or voltage.

Driver Efficiency: This is a measure of luminaire efficiency in terms of the performance of components, power supply, or drivers. It is the ratio of the power derived from the driver divided by the power consumed to operate the driver.

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E

Economic life: These are the number of hours a group of lamps burn before it’s ergonomically advisable to regroup (typically 60% – 75% of rated life).

Efficacy: This is a measurement of light output offered by a light source divided by the total electricity input to that source. It is measured in lumens per watt.

Efficiency: This is calculated as the amount of productive or useful work per quantity of energy used. So, the efficiency of a lighting system is indicated by the luminosity it produces and the amount of energy consumed for the task in a specified time.

Electrolytic Capacitor: This is a type of capacitor that uses an electrolyte as one of its plates, to achieve a larger capacitance per unit volume than other types. Electrolytic capacitors produce excessive amounts of heat, which may damage LED lamps. They are used in relatively high-current and low-frequency electrical circuits, particularly in power supply filters, where they store charge needed to control the output voltage and current fluctuations in rectifier output. They are used as coupling capacitors in circuits where AC should be conducted but DC should not.

Energy: It is quantified as the work done by an electrical system over a specified period of time. It is expressed in kilowatt-hours (kWh).

ENERGY STAR®: This is the designation given to electrical products by the U.S. Department of Energy (DOE) and Environmental Protection Agency (EPA) based on certain criteria such as meeting the required energy efficiency and performance standards.

Enhancing reflections: Reflections which may appear sparkling or glittering and enhance the appearance and aesthetic value.

ESCO: This stands for Energy Saving Service Company. It is a business that offers a variety of energy solutions such as design, implementation, retrofitting of several energy projects. They also offer services related to energy conservation, power generation, risk management, and so on.

ETL Listing: Electrical Testing Labs (ETL) is an electrical safety certification. ETL tests products to the same safety standards as UL listing.

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F

Fenestration: It is the design or arrangement of windows to allow sufficient natural light into the indoor area or transmitting electric lighting from one room to another.

Filament: The wire coil that is heated to produce lighting in incandescent and halogen lamps, normally made from tungsten.

Fitted Target Efficiency (FTE): This is the criteria or standard developed under the draft Energy Star program for outdoor SSL luminaires to measure the luminous efficiency of a luminaire in the targeted area. The FTE calculator uses the selected LM-79-08 absolute photometry IES file for a given luminaire, and projects the output onto a grid on an area nearby the targeted area, such as a street or parking garage floor.

Fixture (Or System) Efficiency: This is a measure of the light performance and it determines the actual amount of light that is transferred from the fixture onto the required area. So, if 90% of the light is used to create luminescence then the fixture efficiency would be 90%. This does not, however, ensure the uniformity of luminescence.

Flat Panel Top LED: It is an LED fixture usually available in surface mountable, pendant, and recessed versions. It is the best alternative for fluorescent lighting systems.

Flicker: It is a phenomenon wherein a lamp blinks continuously, mostly due to either power supply interruptions, or a faulty ballast or driver.

Floodlight: These are high-power lighting fixtures that typically use HID bulbs or their LED equivalents. They are generally used outdoors to emphasize specific objects or areas such as grounds, stadiums, and so on.

Fluorescent Lamp: It is one of the old types of lighting, which was an option for incandescent bulbs but is now easily replaceable owing to the effectiveness of LED lighting. A compact fluorescent lamp (CFL) uses electrodes to stimulate mercury vapor and produce ultraviolet (UV) radiation. This stimulates the phosphor coating of the lamp to produce light.

Fluorescent Tube: This is a particular type of fluorescent lamp equipped with pins at its ends. These pins connect to the voltage output of a ballast. Fluorescent tubes come in standard lengths such as two, four, and eight feet.

Flush Mount Lighting/Flush Mount LED Lights: This type of lighting when mounted onto the ceiling leaves almost no gap between the light and ceiling.

Foot-Candle: It is a unit in which light intensity or illumination is measured. It indicates the amount of illumination the inside surface of a 1-foot radius sphere receives from a point source of one candela in the center of the sphere. One foot-candle is equal to one lumen per square foot.

Formed body arc tube: These are formed through the quartz sculpting process; however, the mass of quartz in them is much lesser than the standard arc tubes.

Frequency: It is the number of occurrences of an alternating current system, which shifts from positive to negative and back. Frequency is expressed in cycles per second or hertz, Hz.

Frosted Lens: It is a translucent white lens which helps diffuse the output of a lamp.

Full-Cutoff Luminaire: This is one of the Illuminating Engineering Society of North America (IESNA) luminaire classifications that prescribe light distribution metrics intended to avoid light pollution. The requirement according to this body requires compliance with the glare produced that reduces the intensity of light. A full-cutoff luminaire in which the luminous intensity (in candelas) at or above an angle of 90° is zero, and the luminous intensity (in candelas) at or above a vertical angle of 80° does not numerically exceed 10% of the luminous flux of the lamps in the luminaire.

Fully-Rated Life: It is an achievement by a device or system that provides useful service for as long as the device or system manufacturer projects. For example, white LEDs are commonly marketed with 50,000 hour fully-rated lives, where the end of life is defined by the point at which the LED fails to deliver at least 70% of initial lumen output.

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G

Gallium Nitride (GaN): It is one of the important types of semiconductor materials used for producing blue LEDs and several electronic devices.

General Lighting: A lighting designed to illuminate a particular area uniformly is termed as general lighting. Candle light bulbs and GLS are some of the best examples of general lighting.  

Ghosting: A light source may produce a faint glow after being turned off due to the presence of current in the circuit. The resulting phenomenon is known as ghosting. It may last for few seconds after the turn off.

Giant Edison Screw: It is a type of cap used in commercial lamps of 500+ watts. This cap is larger than the regular Edison screw cap, and it can be easily screwed into the fitting. Giant Edison screw cap is also referred to as E40 cap.

Glare: A term for visual impairment caused by a light source. The glare is mainly distinguished into two types – discomfort glare and disability glare. The discomfort glare evokes an instant reaction where the person has to close the eyes and look in a different direction. A person may experience this glare when he directly looks to the sun or a potent HID light. However, disability glare may affect the vision, but it is not the same as the discomfort glare. The disability glare does not impair the vision permanently rather it create difficulties in distinguishing the object.

GLS: The classic shape of a bulb. The bulb has a pear shape and narrow base. GLS is an abbreviation for General Lighting Service. They are also known as A-60 or A-shape light bulb.

Goniophotometer: It is a photometric device used to test the intensity of luminous distribution, its efficiency and luminous flux.

Group Relamp: At times, all light bulbs of a particular area are changed at one time, and this phenomenon is known as group relamp. Here, the bulbs are not replaced when they burn out rather the replacement is conducted as a renovation.

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H

Halogen Lamp: These are somewhat like incandescent lamps but a better version of the latter, wherein the lit filament is enclosed in halogen gas. They score better in terms of energy efficiency.

Hard Light: It is a light source that creates shadows sharp edges when the light falls on the object under consideration. It is a type of direct light falling from a focused source. Some examples include floodlights and spotlights.

Harmonic: This electrical frequency is an integer multiple of the fundamental frequency; for instance, if 60 Hz is the fundamental frequency, then 120 Hz is the second harmonic and 180 Hz is the third harmonic. Harmonic distortion occurs in certain electronic devices such as ballasts or power supplies, and it directly affects the power quality.

Heat Dissipation: This is the transition of thermal energy from a hotter object a cooler object. It is type of heat transfer where the excess heat from a hot object dissipates to the cooler ones.

Heat Sink: This is an object that absorbs and dissipates heat from another object using direct or radiant heat transfer.

Hertz, Hz: It is the measuring unit of frequency equal to one cycle per second.

High-Bay Lighting: These are lighting systems designed for high ceiling heights of about 25’ or more, mostly found in sports complexes and warehouses.

High-Efficiency Plasma (HEP): This is a relatively new lighting technology that uses radiofrequency to stimulate a contained gas and create a bright ball of plasma. It has an extremely high efficacy (over 90 lumens per watt) and perfect color rendition (CRI = 100). This may offer competition to LED in the years to come.

High Intensity Discharge (HID):  This is a type of electrical lamp that illuminates by striking an electric arc between tungsten electrodes. These electrodes contain certain gases and compounds. Although the color quality of these lamps may not be great, they have a high efficiency and operational life.

High-Output (HO) Lamp: These are an improved version of the traditional fluorescent tubes. They are better in terms of high lumen output and rated power.

High Power LEDs: These are LEDs designed to operate at several hundred milliamps of power. Since these devices generate a lot of heat which may even damage the unit, specialized heat dissipation technologies are implemented in these LEDs.

High Pressure Sodium (HPS): High intensity discharge (HID) is a type of with a good operational life, energy efficiency, fairly high correlated color temperature (CCT), and an average level of color rendering index (CRI).

High Voltage Lamps: These are a type of lamps that can function at a high voltage and offer naturally diffused or scattered light.

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I

IALD: It stands for the International Association of Lighting Designers. As its name implies, it is a global association that promotes lighting design excellence while offering professional training and scholarship to lighting designers.

IEEE: Abbreviation of the Institute of Electrical and Electronics Engineers is the world’s largest association of technical professionals with over 400,000 employees. Its aims the educational as well as technical advancement of electrical and electronic engineering, computer engineering, telecommunications, and many more.

IESNA: It stands for the Illuminating Engineering Society of North America. Founded in New York City, it is one of the technical authorities in the lighting industry to improve the lighted environment while bringing all lighting knowledge and translating it into actions that profit the public.

Illuminance: The term is defined as the intensity of light arriving at a surface per unit of area. Higher illuminance indicates the brighter light emitted on the surface. Illuminance is measured in two units as follows:

  • Foot-candle – Which is equivalent to one lumen per square foot.
  • Lux- Which is equivalent to one lumen per square meter.

Illumination: Act of supplying light for decorative or practical purposes.

Incandescence: The phenomenon of light caused by heat is called incandescence. Anything lights up from the heat, emotionally or physically, it produces incandescence. Some examples include a shooting star, the glow of a candle, an incandescent filament lamp, etc.

Incandescent Lamp: The incandescent lamp also called an incandescence light globe or lamp. It is an electric light that features a tungsten filament heated or glows when it carries current. These lamp has come with a perfect color-rendering index of 100, as compared to that of sun. However, it is considered the least efficient lighting types.

Infrared Radiation, IR: Also referred to as infrared, it is a region of the electromagnetic radiation given off by fluorescent lighting.

Indirect Lighting: Indirect lighting is increasingly popular in both commercial and residential projects. Sometimes called up-lighting, it is all about concealing the light onto the upper walls without letting the viewer see it.

Induction Lamp: It is a high-performance ferrite core with an induction coil, which transfers the power required to generate light from outside lamp cover to the gas inside. These lamps are a surprisingly promising technology that offers long life and excellent efficiency.

Initial Lumens: The total number of light given off by a particular lighting device just after it stabilized, but before the loss of operational efficiency. The initial lumens values for high-density discharge (abbreviated as HID) and fluorescent bulbs are measures during the first 100 hours of operation of lighting devices.

Instant Start Ballast: This energy-efficient lamp ballasting method applies a high voltage across the lamp without preheating the cathode. This method makes use of 1.5 to 2 watts less than other ballast methods. One of the major drawbacks of this method is they don’t assure the lifelong service of the lamp.

Insulated Ceiling Fixture: As its name implies, these lighting fixtures are in direct contact with insulation as they are directly placed into the ceiling. Unlike other lighting fixtures, they emit less heat.

Indoor Positioning: A technology that enables locating the position of the people or objects within places like airports, parking garages, inside multistory, buildings, and underground locations. Indoor positioning systems (IPS) use different technologies including distance measurement technique, dead reckoning, magnetic positioning, and more.

Integrated Lighting Fixture: These types of lighting fixtures offer superior energy efficiency by using internal geometry and a superiorly designed LED array. These lighting fixtures are more expensive than lamp-based LED fixtures, but they are easier to control in terms of dimming.

Interior Soffit Lighting / Soffit Light Fixtures: This type of lighting is specially designed for the portion of the ceiling that is smaller than the main surface. For example, the fixture installed on a beam, or above the kitchen sink, or the underside of a balcony.

International Dark-Sky Association (IDA): A United States-based non-profit authority that aims to protect and preserve night time environment using high-quality outdoor lighting.

IP Rating: Also interpreted as Ingress Protection Rating, it is a two-digit code that shows the resistance of lighting fixture to liquid as well as solid particles. The first digit shows the protection against solid particles, whereas the second digit shows the protection degree against liquid particles.

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J

Joule: It is a derived unit of work or energy. The term defined as the total amount of energy transmission to a particular object in the direction of motion through 1-meter distance. A joule is equal to 1 watt of power emitted for one second.

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K

Kelvin Temperature (K): It is a measurement unit for temperature. In the lighting system, it indicates CCT (Correlated Color Temperature) of the various light sources.

Kilowatt (kw): It is a unit of electric power, which is equivalent to a thousand watts. This term is entirely different from kilowatt-hour. 

Kilowatt- hour (kWh): It is a measurement unit for energy consumption. As its name implies, it is defined as the total amount of energy consumed by a one-kilowatt appliance for one hour. Various electric utility bills are calculated using kilowatt-hour consumption. Do not get confused with kilowatt and kilowatt-hour.

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L

L70: It is described as 70% of the initial lumens level from an LED light bulb during their rated life. This measurement shows how long you can depend on the LED bulb to provide intensity from the day you installed it.

Lamp: The specific replaceable component that emits light from electricity is called a lamp. Sometimes referred to as lights bulbs, the lamp has a base made of plastic, ceramic, glass, metal, and glass, which secures the lamp in a light fixture socket. The example of electric lamps is high-density discharge, incandescent, and fluorescent.

Lamp Life: 666nn

Lamp Sources: It is a comprehensive range of electric lighting components – incandescent, fluorescent, and high-intensity discharge (HID) lamps that produce light from electricity is called a lamp, also known as traditional lamps. LEDs are also considered as lamps.

Light Emitting Diode (LED): An electronic device that emits lights when exposed to electric current. Owing to its energy efficiency and long lifespan feature, they are commonly used across various applications, including electronic signs, flashlights, clock displays, and many more.

Lighting Design Lumens (LDL): It is a simplified method to calculate the total number of lumens available in a room divided by the room area.

LEED: Leadership in Energy and Environmental Design, shorten as LEED, is one most popular green building certification programs across the world, which includes the rating systems for the construction, operation, design, and maintenance of green buildings. The program aims to help building operators and owners to be environmentally responsible.

LED Array: It describes the group of LEDs on the printed circuit board (PCB), or any other surface, capable of producing light when power is on.

LED Driver: Also known as LED power supplies, which regulates the power required for arrays of LED lighting. Several LED drivers make use of the Electrolytic Capacitor to achieve constant current. They also protect LEDs from over-voltages, voltage spikes, and normal voltage fluctuations.

LED Efficiency: It is a relationship of lumens per watt, which means a measure of LED device output, divided by the power required to operate the individual output.

LED Junction Temperature (TJ): The active region of LEDs at which the diode connects to the base. The low junction temperature of diode not only produces more light but at times reduces lumen depreciation. The junction temperature of the diode is affected by several reasons, including the thermal path, the ambient temperature, and the driver current.

LM-79: A standardized document that measures the photometric and electrical properties of LED lighting products. This LED measurement standard provides a proper and repeatable measurement of LED lighting systems to photometric labs.

LM-80: It is one such standard that refers to a method for measuring the depreciation of several solid-state lighting sources including modules and arrays, LED packages. The method describes how to measure a single part of an LED luminaire under certain set conditions over a period of time. It is a beneficial tool for lightning professionals, who are looking to examine LED products; however, it is not meant for LED system reliability and performance.

Low Pressure Sodium (LPS): LPS lamps, also termed as a Miscellaneous Discharge Lamp (MDL), offering high-levels of efficiency, an extremely warm color temperature (CCT), and long-lasting life. It is a gas discharge lamp that makes use of sodium to produce light. LPS lamps are cost-effective, thus they can be used in security, and road lighting where the object color is not important. They are suitable for foggy weather.

Lumen: Lumen is recognized as a standard international unit for measuring light. It is a measure of luminous flux that indicates the quantity of light emitted by an LED lamp.

Lumen Depreciation: It is the gradual decrease in lumen output of a light source over time due to LED darkening.

Lumen Maintenance: It is an approach of measuring the amount of light produced by a source when it is new and compares it with light output over time in the future. L50 and L70 are common examples of lumen maintenance. Lumen maintenance is expressed as Lp of x hours, wherein:

L – Initial light output

P – Percentage of light maintained over x hours.

Lumen Output: It is a new way of knowing how a bright lamp is. Lumen output is the total number of visible light to the human eye from a light source.

Lumens per Watt (LPW): It refers to the energy efficiency of lighting. LPW is a measure of light output per unit of energy consumption.

Luminaire: It is a complete lighting unit with one of these components: ballast, lamp and lamp sockets, reflective materials such as lenses, blades, refractors or other shielding. Socket helps to hold the lamp in the place and protect it. Reflective materials direct as well as distributes the light in the space, and wiring connects the light to its power source. Efficient luminaires are good at optimizing the performance of each of these components.

Lux (lx): It is a measurement unit for illuminance, which is equivalent to one lumen per square meter. In simple words, lux is described as a metric to measure the intensity of light passing through the application surface.

Lens: It is a luminaire component aims of dispersing, conversing or diverging the lighting output to achieve the desired distribution pattern.

Low-voltage Lighting: Unlike other types of lightning, low-voltage lights are safer to use. They typically use 12 or 24 volts and require transformers that lower the line or high voltage from 120 volts. The transformer used for low-voltage lighting is either located remotely or build into the fixture.

Luminous Efficacy: A measurement unit that indicates how a light source emits visible light using a given amount of power. Luminous efficacy is measured in lumens per watt (LPW).

Lamination: It is a process of arranging material in thin layers, thus, the composite material is stable for a long time.

Lamp Lumen Depreciation: The progressive decrease in the luminous output of a light source over time. Each lamp type has a different lumen depreciation curve, which shows the pattern of decreasing light output.

Lampholder: A device that holds a light bulb or lamp is called a lamp-holder.

Layering Light: An ambient lighting approach that combines different lights to create a mood or ambiance.

Lensed Troffer: A rectangular light fixture that is coveted using lens. Troffers are capable of making the lighting eliminating glare and more uniform.

Light Loss Factor (LLF): Formerly referred to as maintenance factor, it is used to account for the illumination of the lighting system after a given period of time under general conditions, such as dust accumulation, lens degradation, lamp depreciation due to voltage surges, and more.

Light Pollution: Also called luminous pollution, it is imprudent, mismanaged or intrusive use of artificial lighting systems. The excess level of light pollution alters the color of the nighttime sky, disrupts circadian rhythms, eclipses natural starlight which affects the energy resources, environment, wildlife, and more. One common example of light pollution is parking light fixtures. The threat of light pollution continues to grow as the demand for artificial lighting system increase in the upcoming years.

Light Scallops: A light that has been recessed into a ceiling and throws light downwards in a narrow beam. The light scallops create a real mood and ambiance to a room.

Light Transformer: Also called as dimmer switches, they are utilized to make the light brighter or dimmer. They serve as isolation between primary and secondary supply, also restricts high voltage spikes and short circuit current in the load.

Linear Lighting: A high-end flexible decorative lamp uses multiple light-emitting diodes in a single strip. Unlike other common light fixtures, they are advantageous for indoor and outdoor entertainments, building innovative, clean and dynamic lighting environments, and the production of billboards.

Low-Bay Lighting: The lighting system designed for use in a ceiling under 25 feet in height from the floor. It is one common type of ceiling used in most retail businesses, public buildings, and homes.

Low Voltage Track: It is one of the modern track options that works at a low voltage using a step-down transfer.

Lumens to Watts: Wattage describes the amount of energy used by a light source, while lumen merely indicates the amount of light emitted by it. As lighting becomes more energy-efficient, the same number of lumens is achieved with lower wattages. Both watts and lumen units represent different quantities, thus, one can easily convert lumens to watts using the following formula.

The power in watts is equivalent to the luminous flux in lumens, divided by the luminous efficacy in lumen per watt.

P(W) = ΦV(lm) / η(lm/W)

watts = lumens / (lumens per watt)

Luminaire Dirt Depreciation: As its name suggests, the term describes the output reduction of luminaire due to an excess level of dust.

Luminance: It is a reflection of light perceived by human eyesight in a specific direction. Luminance is measured in candelas per square meter, and its changes depend on the viewing angle.

Luminous Ceiling: A translucent ceiling panel that emits light from the entire surface using fluorescent strip lights.

Luminous Flux: Also called luminous power, it is the measure of the light emitted by a light source. The lumen is the standard unit of luminous flux.

Luminous Intensity: It is the measure of the wavelength –weighted power in a particular direction. The candela is the standard unit of luminous intensity.

Line-Voltage LED: As its name implies, it is a complete set of luminaires that uses line-voltage wiring for transforming power downwards. This system can be operated directly with a standard voltage of 120 volts, which is common in the US and Canada.

LED Conversion/LED Retrofit: The process of replacing the existing lighting with new, better, and more efficient lighting is called LED conversion. The method of replacing inefficient lighting to efficient, preferably resulting in increased quality and energy efficiency of the light.

Lighting as a Service (LaaS): LaaS is one popular service which delivers highly efficient and instant energy savings lighting solution with no upfront investment.

Lighting Audit: It is one of the effective and simplest ways of determining which lighting systems need to update or replace. Also, you will evaluate the existing lighting system and return on investment.

Light Center length (LCL): LCL measures the distance between the center of the filament and the bottom of the lamp base.

Lamp Lumen Depreciation Factor (LLD): It is the process wherein a lamp constantly emitting lower light over a defined period.

Lamp Voltage: A voltage across which the lamp operates when they are fully charged.

Level of Illumination: A considerable amount of light arriving at a surface. Illuminance is measured in lux or foot-candles.

Luminance Contrast: The term describes the relationship between the object, luminance, and its background.

Luminance Ratio: A ratio of luminance from different areas in the visual field.

Light on Centers (LOC): The distance between different LED Lighting systems.

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