GLOSSARY OF LIGHTING TERMS

2C/2N(2circuit 2Neutral) Track: A 4-wire track system, with 2 Live and 2 Neutral connection. There has 120VAC and 277VAC option.

AC(Alternating Current): The flow electricity(electric current) in a circuit that alternates direction every second with a standard current frequency of 50Hz/60Hz.

Accent Lighting: Directional lighting to emphasize a particular object or surface feature, or to draw attention to a part of the field of view.

Airtight: Not allowing air to escape or pass through the holes. Normally, a downlight request a hole on ceiling for mounted, with airtight downlight, it can stop the air circulation.

Ambient Temperature (Ta): The air temperature surrounding the device.

American National Standards Institute (ANSI): The organization that coordinates voluntary guidelines and standards for the electrical and other industries.

Annulight: A trade mark of Kinglumi Co., Ltd.

ANSI Binning: The system defined by the American National Standards Institute for the binning specifications for light emitting diodes.

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

Barndoor: A set of adjustable flaps—usually two, four, or eight—that may be attached to the front of a luminaire (usually a Fresnel spotlight) speed ring or to an accessory holder in order to partially control the shape and spread of the light beam.

Beam Angle (Spread): The central part of the beam of light from a reflector lamp (i.e. BR, MR and PAR types) where the intensity is 50% of the maximum candle power.

BBBL: The Chromaticity Coordinate of LED is below the Black Body Curve.

Black Body / Black Body Radiator: An object that absorbs all electro-magnetic radiation falling on it. Because it reflects no light, a black body appears black. As a black body is heated to incandescence, it radiates light in a sequence of colors, from red to orange to yellow to white to blue, depending on its temperature. This color sequence describes a curve within a color space, known as the black-body curve.

Black Body Curve: A curve within a color space describing the sequence of colors emitted by a black-body radiator at different temperatures.

Brightness: The attribute of a visual sensation according to which an area appears to emit more light or less light.

CAMETA: A trade mark of TIR lens developed by Kinglumi Co., Ltd. in 2010, with Chinese patent.

Candela (cd): The measuring unit of luminous intensity of a light source in a given direction. A light source may have different intensities depending upon the given direction which the measurement is taken. The old measurement equated to the amount of light produced by a standard candle.

Candlepower (cp): Luminous intensity expressed in candelas. Typically used in measuring the luminous intensity distribution of a reflector lamp or lighting fixture.

Case Temperature: The temperature measured at the LED package or case.

Center Beam Candle Power (CBCP): The intensity of light produced at the center of a reflector’s beam, expressed in candelas.

Chromaticity: An objective specification of the quality of colour regardless of its luminance.

Coefficient of utilization(CU): The ratio of luminous flux (lumens) calculated as received on the work plane to the total luminous flux (lumens) emitted by the lamps alone. It is equal to the product of room utilization factor and luminaire efficiency.

Color Rendering Index (CRI): An index from 0-100 measuring a light source’s ability to render color accurately. Sodium lamps can have a CRI as low as 22, while tungsten Halogen lamps can have a CRI as high as 100. Any lamps rated above 80 CRI tend to be of good color rendering.

Color Temperature: The measure of the color appearance of a light source which describes the apparent warmth of coolness of that light source.

Compact Fluorescent Lamp (CFL): The standard term given to small diameter Fluorescent lamps, some of which have built-in ballasts and medium screw bases for replacement of Incandescent lamps.

Cones: Retinal receptors that dominate the retinal response when the luminance level is high and provide the basis for the perception of color.

Constantly Current: A circuit in which the current remains constant but the voltage may vary.

Current: A measure of the rate of flow of electricity, expressed in amperes.

DALI(Digital Addressable Lighting Interface): A digital communications protocol for controlling and dimming lighting fixtures, originally developed in Europe.

Die-casting: A metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process.

Diffuser: A device to redirect or scatter light from a source, primarily by the process of diffuse transmission.

DIM: To reduce the illuminance produced by a luminaire. Though mechanical means may be utilized (see iris), the usual reference is to the use of an electrical dimmer.

Dimmable: A lamp that has varying lumen output controlled by dimming device.

Dimmer: An electronic device used to vary the lumen output of a lamp.

DIM to Warm: A products are suited for hospitality and entertainment venues such as hotels, restaurants, cafeteria and theatres, where there is a desire to mimic the behavior of incandescent lamps. When delivering maximum light output, the color is white, but when lighting is dimmed, the CCT drops to simulate dimmed incandescent or candlelight. Judges observed that the color quality in the submitted product was stellar, even at the lowest end of the dimming range.

Direct Current (DC): A type of electrical current and distribution by which electricity flows in one direction through the conductor. Battery operated systems are typical DC applications. (See Alternating Current)

Direct Lighting: Lighting involving luminaires that distribute 90% to 100% of the emitted light in the general direction of the surface to be illuminated. The term usually refers to light emitted in a downward direction.

Downlight: A small direct-lighting unit that directs the light downward and can be recessed, surface mounted, or suspended.

Efficacy: The measured effectiveness at which lamps convert power (measured in watts) into light (measured in lumens). Also see Lumens Per Watt.

Emergency Lighting: Lighting designed to supply illumination essential to the safety of life and property in the event of failure of the normal supply.

Energy Policy Act (EPACT): Energy legislation passed in 1992 by the U.S. Congress. The law involves a variety of different industries including lighting. The lighting section of the legislation covers lamp labeling and minimum energy efficiency standards (lumens/watt) for many commonly used lamps including incandescent and Fluorescent sources.

ELV-type Dimmer: An electronic low voltage dimmer, used to dim LED lighting fixtures with electronic transformers.

Extrusion: a process used to create objects of a fixed cross-sectional profile. A material is pushed through a die of the desired cross-section.

Field Angle: The angle between the two directions for which the intensity is 10% of the maximum intensity as measured in a plane through the nominal beam centerline. For beams that do not possess rotational symmetry, the beam angle is generally given for two planes at 90 degrees, typically the maximum and minimum angles. Note that in certain fields of application the angle between the 10%-of-maximum directions was formerly called beam angle.

Flicker Index: A measure of the cyclic variation in output of a light source, taking into account the waveform of the light output. It is the ratio of the area under the light output curve that is above the average light output level to the total area under the light output curve for a single cycle.

Flicker Percentage (Flicker %): A relative measure of the cyclic variation in output of a light source (percent modulation).

Fluorescent Lamp: A low-pressure mercury discharge lamp in which an electric discharge of ultraviolet energy excites a coating of phosphor on the lamp glass and transforms some of that energy to visible light. Fluorescent lamps are manufactured in many different forms including linear four foot T8 lamps, U-shaped and Coiled Compact Fluorescent lamps with integrated ballasts. Fluorescent lamps typically require a matching ballast to operate the lamp properly.

Forward voltage: LEDs are current driven devices. If an external current is passed through the device, a forward voltage will be devel-oped across the diode.

Frequency: The number of times per second that an alternating current system reverses from positive to negative and back to positive, expressed in hertz (Hz).

General Lighting: Lighting designed to provide a substantially uniform level of illuminance throughout an area, exclusive of any provision for special local requirements.

GLOBAL Track Adapter: A 4wire 3Circuit track adapter, compatible with GLOBAL pro three-circuit system (GLOBAL is a registered trademark of Nordic Aluminium).

Goniophotometer: A photometer for measuring the directional light distribution characteristics of sources, luminaires, media, and surfaces.

Halogen Lamp: A higher pressure, high temperature incandescent lamp containing Halogen gas that recycles tungsten back onto the filament surface. The Halogen cycle allows for higher efficacy, higher color temperature, and longer life cycles than incandescent lamps.

Heat Sink: A part of the thermal system that conducts or disperses heat away from sensitive components, such as LEDs and electronics.

Hertz (Hz): A unit of frequency equal to one cycle per second (see Frequency). The U.S. standard is 60 Hz.

High Power LED: A high power LED, sometimes referred to as a power LED, is one that is driven at a current of 350mA or higher.

High Intensity Discharge Lamp (HID): A high pressure lamp in which high intensity light is produced by an electrical arc source. General terminology for Mercury lamps, Metal Halide lamps, High Pressure Sodium lamps, High Pressure Xenon lamps, or any other high intensity arc discharge source.

H-Type: A track adapter, compatible with Halo 3wire 1circuit track system(Halo is a registered trademark of Cooper Lighting).

IC Downlight: A downlight which designed to allow insulation thermal materials to direction covered it.

Illuminance: E=dΦ/dA, The areal density of the luminous flux incident at a point on a surface.

Illumination: An alternative, but deprecated, term for illuminance. It is sometimes used because illuminance is subject to confusion with luminance and illuminants, especially when not clearly pronounced.

Indirect Lighting: Lighting involving luminaires that distribute 90% to 100% of the emitted light upward.

Initial Lumens: The luminous output of a new light source. Quantity of light output measured after 100 hours of operation using controlled system characteristics.

Inrush Current: The current generated during the initial start up of a lamp system. Inrush current can be several times higher than the operating current of a lamp.

Integrating Sphere: A hollow sphere whose internal surface is a diffuse reflector and is as spectrally non-selective as possible.

Isolux (isofootcandle) line: A line plotted on any appropriate set of coordinates to show all the points on a surface where the illuminance is the same. A series of such lines for various illuminance values is called an isolux (isofootcandle) diagram.

J-Type: A track adapter, compatible with Juno 1 circuit track system(Juno is a registered trademark of Juno Lighting).

Junction Box: A box containing a junction of electric wires or cables.

Junction Temperature: Junction temperature, noted as Tj, is the temperature of the LED’s active region.

Kelvin: A unit of color temperature measurement. (See Correlated Color Temperature).

Kilowatt (kW): A measure of electrical power equal to 1000 watts.

Leadership in Energy & Environmental Design (LEED): The U.S. Green Building Council’s (USGBC) green building certification program that requires buildings to satisfy certain prerequisites to achieve different levels of certification.

Leading Edge Dimmer: A type of dimmer that regulates power to lamps by delaying the leading edge of each half-cycle of AC power. Compatible with many LED fixtures.

LED Array or Module: An assembly of light emitting diode (LED) packages (components), or dies on a printed circuit board or substrate, possibly with optical elements and additional thermal, mechanical, and electrical interfaces that are intended to connect to the load side of an LED driver. Power source and ANSI standard base are not incorporated into the device. The device cannot be connected directly to the branch circuit.

LED Chip (Chip): The light producing semiconductor device that may or may not be incorporated into an LED.

LED Driver: A device composed of a power source and light emitting diode (LED) control circuitry designed to operate an LED package (component), an LED array (module), or an LED lamp.

LED Light Engine: An integrated assembly comprised of LEDs or LED arrays, LED driver, and other optical, thermal, mechanical, and electrical components.

LED Luminaire: A complete lighting unit consisting of light emitting diode (LED)-based light emitting elements and a matched driver together with parts to distribute light, to position and protect the light emitting elements, and to connect the unit to a branch circuit. The LED-based light emitting elements may take the form of LED packages (components), LED arrays (modules), an LED light engine, or LED lamps. The LED luminaire is intended to connect directly to a branch circuit.

Lens: A transmitting element used to change the direction and control the distribution of light rays.

Light distribution curve     A three dimensional shape describing the light distribution from a light source or a luminaire.

Light efficiency of a luminaire  A value given in lm/W, describing the ratio of the luminous flux emitted by a luminaire and the energy consumed by it.

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

Light Intensity(cd): The amount of light falling on a given point.

Lifetime: The estimated period in working life span.

LM-79: Photometric testing report for LEDs that contains information such as lumens, color temperature, power, current, etc.

LM-80: Testing report for LEDs that contains information on the lifespan of the LED.

L-Type: A track adapter, compatible with Lightolier 2wire 1circuit track system(Lightolier is a registered trademark of Philips Lighting).

Lumens: The international unit of measurement for light. A measurement of total quantity of light output from an electric lamp in all directions for a given unit of time. (See Initial Lumens and Mean Lumens)

Lumens Per Watt (LPW, lm/W): Efficacy; Lumen output divided by lamp watts consumed.

Lumen Depreciation: The decrease in lumen output of a light source over time, until failure.

Luminaire (Light fixture): A complete lighting unit consisting of a lamp(s) and ballast(s) (when applicable), together with the parts designed to distribute the light, to position and protect the lamps, and to connect the lamps to the power supply.

Luminaire Efficiency: The ratio of luminous flux (lumens) emitted by a luminaire to that emitted by the lamp or lamps used therein.

Luminaire Power: The total power consumption of a luminaire.

Luminaire Spacing Criterion(SC): A classification parameter for indoor luminaires relating to the distribution of the direct-illuminance component produced on the work plane. The spacing criterion of a luminaire is an estimated maximum ratio of the luminaire spacing to the luminaire mounting height above the work plane for a regular array of that luminaire such that the work plane illuminance will be acceptably uniform.

Luminance: Photometric brightness, luminance is a measure of the flux emitted from, or reflected by, a relatively flat and uniform surface. Luminance may be thought of as luminous intensity per unit area. Candelas per square meter (cd/m2).

Luminous flux – LED: The total combined luminous flux of all LED sources installed in a luminaire, given as the diode’s nominal temperature.

Luminous flux – luminaire: The total luminous flux of the luminaire, taking into account all losses resulting from the optical systems used, the temperature

Luminous intensity of a LED: The power of the LED-modules installed in a luminaire.

Lux (lx): An international metric unit of luminance. One lux is equal to 1 lumen per square meter (see footcandle). 1 lx = 1 lumen per square meter (lm/m2).

MacAdam Ellipse: A MacAdam ellipse is the region on a chromaticity diagram which contains all colors which are indistinguishable, to the average human eye, from the color at the center of the ellipse.

MCPCB: A widely accepted Printed Circuit Board (PCB) material with a Metal Core (MC) for better thermal performance.

Metal Halide Lamp: A member of the high intensity discharge light source family. The light from this source is produced by the radiation from mercury, together with halides of metals such as sodium, scandium, indium and dysprosium. Metal Halide light sources typically require a matching ballast to operate the lamp properly. Metal Halide lamps are available in single-ended and double-ended varieties. Lamp design varies from tubular to elliptical shapes.

Modular design: A design approach that subdivides a system into smaller parts called modules, which can be independently created and then used in different luminaires. A modular system can be characterized by functional partitioning into discrete scalable, reusable modules.

Operating Current: Steady state current consumed by a lamp at rated watts.

Phosphor: An inorganic chemical compound processed into a powder and deposited on the inner glass surface of certain discharge lamps. Phosphors absorb short wavelength ultraviolet radiation, transforms it and emits it as visible light.

Photobiological Hazard: The possible risk of biological injury due to optical radiation.

Photobiology: A branch of biology that deals with the effects of optical radiation on living systems.

Photometer: An instrument for measuring photometric quantities such as luminance, luminous intensity, luminous flux, or illuminance.

Planckian Black Body Locus: The line on the CIE Chromaticity Diagram that describes the color temperature of an object when heated

Power Factor (PF): A measure of the effectiveness of which an electrical device converts amperes to watts. Power factors can range from 0 to 1.0. A high power factor means that an electrical system is utilizing power efficiently. Devices with power factors of greater than 0.90 are considered “high power factor.”  from approximately 1,000K to more than 10,000K.

Projector: A lighting unit that, by means of mirrors and lenses, concentrates the light into a limited solid angle so as to obtain a high value of luminous intensity.

Ra: An average value of color rendering index R1 to R8, which measuring a light source’s ability to render color accurately.

Reflection: A general term for the process by which the incident flux leaves a (stationary) surface or medium from the incident side, without change in frequency.

Reflectivity: Reflectance of a layer of a material of such a thickness that there is no change in reflectance with increase in thickness.

Reflector: A device used to redirect the flux from a source by the process of reflection.

SDCM: See Standard deviation of color matching (SDCM)

SMDs: Surface-mount LEDs.

Snoot/Funnel: In television, film and theater lighting: A metal tube that can be mounted on the front of a spotlight to control stray light.

Soft Light: Diffuse illumination that produces soft-edged, poorly defined shadows on the background when an object is placed in its path; A luminaire designed to produce such illumination.

Solid Angle: A measure of that portion of space about a point bounded by a conic surface whose vertex is at the point. It is defined as the ratio of intercepted surface area of a sphere centered on that point to the square of the sphere’s radius. It is expressed in steradians.

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

Spacing-to-mounting-height ratio(S/MH): The ratio of the actual distance between luminaire centers to the mounting height [see mounting height, MH (interior)].

Spotlight: A form of floodlight usually equipped with lens and reflectors to give a fixed or adjustable narrow beam.

Standard deviation of color matching (SDCM): Describes the difference between two colors. A difference of one to three SDCM “steps” is virtually imperceptible, a difference of four SDCM steps is just noticeable, and a difference of more than four SDCM steps is readily visible.

Surface Mounted Luminaire: A luminaire that is mounted directly on a wall or on the ceiling.

Suspended (pendant) Luminaire: A luminaire that is hung from a ceiling by supports.

Thermal Management: Controlling the operating temperature of the product through design, examples include heat sinks and improved airflow.

Thermal Resistance (K/W): The property of a material’s ability to conduct heat.

Total Harmonic Distortion (THD): A measure of the distortion of an electrical wave form. THD is expressed in percent and may refer to individual electrical loads (such as a ballast). The ANSI recommendation is for THD to be no greater than 24%.

Trailing Edge Dimmer: A type of dimmer that regulates power to lamps by delaying the end of each half-cycle of AC power. Compatible with many LED fixtures.

Triac Dimmer: TRIAC dimmers are designed for resistive loads such as incandescent or halogen lights and have a significant installed base in the worldwide.

Tunable White Light: White-light LED fixtures that combine channels of warm white and cool white LEDs to produce a range of color temperatures.

UGR(Unified Glare Rating): The unified glare rating is a formula for measuring glare levels, calculated for lightning systems at the design stage.

Ultraviolet (UV): The portion of the electromagnetic spectrum in which the longest wavelength is just below the visible spectrum, extending from approximately 4nm to approximately 400nm.

Voltage: The force or the pressure of electricity. For incandescent and Halogen lamps, voltage generally refers to the line voltage of which the lamp should be connected. For HID, Fluorescent, and Low-Voltage lamps, the voltage generally refers to the operating voltage which the lamp is connected to a power supply (ballast or transformer) after it has warmed up.

Wavelength: Distance between two successive points of a periodic wave. The wavelengths of light are typically expressed in nanometers (nm), or billionths of a meter.

Working Temperature: Temperature range in which the luminaire can be safely used.

Work Plane: The plane on which a visual task is usually done, and on which the illuminance is specified and measured. Unless otherwise indicated, this is assumed to be a horizontal plane 0.76 meters (30 inches) above the floor.