Absorption Conversion of light to heat by interaction with matter. Accent Lighting Directional lighting to emphasize a particular object or to draw attention to the field of view. Alternating Currect (AC) Flow of electricity which cycles of alternates direction many times per second. The number of cycles per second is referred to as frequency. The most common frequency used in this country is 60 Hertz (cycles per second). Amalgam A mixture of mercury and other metals used in Compact Fluorescent lamps to allow the lamps to have a stable light output over a wide range of temperatures and burning positions. The amalgam causes the lamp to have a 60 second warm-up time. Ambient Lighting General lighting, or lighting of the surrounding area. American National Standards Institute (ANSI) A consensus organization which coordinates voluntary standards for the physical, electrical, and performance characteristics of lamps, ballasts, luminaires, and other lighting and electrical equipment. Amperes (amps or A) The unit of measurement of electric current. The is current related to voltage and power as follows: Current (amps) = Power (watts)/Voltage (volts). Arc Discharge (in gas or vapor) Electric discharge that produces light without a filament. Average Illuminance (Eav) Over a surface. Illuminance averaged over the specified surface. Ballast Device used with fluorescent and HID lamps to provide necessayr starting voltage and limit the current during operation. Base The end of the lamp that inserts into lamp socket. Beam Spread The angle over which the intesity of the beam drops to 50% of its peak intensity. Measured in degrees. Brightness A visual sensation that describes how much light an area appears to emit. There are no units of measure for brightness; its measurement is relative .In other words, more or less bright. British Thermal Units (BTU's) Measurement of heat produced Unit BTU, BTUs per hour = Watts X 3.413 Bulb The glass outer or envelope of a lamp. Also, a lamp is commonly referred to as a bulb. Burning Position The position in which a lamp is designed to be operated. Canadian Standards Association (CSA) An organization that writes standards and tests lighting equipment for performance as well as electrical and fire safety. Canadian provincial laws generally require that all products sold for consumer use in Canada must have CSA or equivalent approval. Candela The unit of measure for intesity in a given direction. The term has been retained from the early days of lighting when a standard candle of a fixed size and composition was used as a basis for evaluating the intesity of other sources. Candlepower (CP) The intesity or the strength of the beam in a given direction. Unit candela, cd. Chromaticity See color temperature Class "P" Ballast Contains a thermal protective device, which deactivates the ballast when the case reaches a certain critical temperature. The device resets automatically when the case temperature drops to a lower temperature. Color Appearance The color impression when looking directly at a light source. Color Rendering Expression for the effect that the light has on the color appearance of objects. Color Rendering Index (CRI) of a light source. A scale from 0-100 that describes how natural the color of objects will appear as compared to a standard light source (100 CRI). The standard light sources are Incandscent/Halogen bulbs (100 CRI) for warm sources and Natural Daylight (100 CRI) for cool sources. Color Temperature A term used to describe the "whiteness" of light. It is the temperature of a piece of metal (or black body) that emits the same color light as the compared light source. Unit Kelvin, K. Compact Fluorescent Lamp (CFL) The general term applied to families of smaller diameter fluorescent lamps, some of which have built-in ballasts and medium scew bases for easy replacement of incandescent lamps. Cone Photoreceptors in the retina containing light-sensitive pigments responsible for seeing color. Contrast The difference between the object and its background. Cornice Lighting Lighting system comprising light sources shielded by a panel parallel to the wall and attached to the ceiling, distributing light over the wall. Correlated Color Temperature The temperature of a piece of metal whose perceived color most closely resembles that of a compared light source at the same brightness. Unit Kelvin, K. Cosine Law of Incidence The law that states that illuminance at a point on a plane is proportional to the cosine of the angle of light incidence (the angle between the direction of the incident light and the normal to the plane). E+I/d2 cos Cove Lighting Lighting system comprising light sources shielded by aledge or recess, and distributing light over the ceiling and upper wall. Diffuse Reflection Diffusion by reflection in which, on the macroscopic scale, there is no regular reflection. Diffused Lighting Lighting in which the light is not coming mainly from one particular direction. Diffuser Device used to alter the distribution of light and depending essentially on the phenomenon of diffusion. Diffusion (scattering) Change of the distribution of a beam of light when it is deviated in many directions by a surface or by a material. Dimmer A device in the electrical circuit for varying the light output from lamps in a lighting installation. Dimming an incandescent lamp extends its life. DiOptic Reflector A segmented, dual parabolic reflector that increases the reflector efficiency up to 20%. Direct Current (DC) Flow of electricity continuously in one direction. Direct Glare Glare resulting from high luminances or insufficiently shielded light sources in the field of view. Direct Lighting Lighting by means of fixtures or luminaires that have 90 to 100 percent of the light reaching the working plane directly. Directional Lighting Lighting in which the light on the working plane or on an object is coming predominately from one particular direction Discharge Lamp Lamp in which the light is produced, directly or indirectly, by an electric discharge through a gas, a metal vapor, or a mixture of several gases and vapors. Discomfort Glare Glare that causes discomfort without necessarily impairing the vision of objects. Dispersion To split light into the colors of the rainbow. Distance (D) The distance from the light source to the working plane. Downlight (Can, High Hat) Small luminaire, which distributes the light downward, usually recessed in the ceiling. Efficacy Of a source. Efficacy is the rate at which lamp is able to convert electrical power (watts) into light (lumens), expressed as lumens per watt. Divide light produced (lumens) by the power consumed (watts). Lumens/Watts = LPW. Unites lumen per wall LPW, lm/W Efficiency Often misused term in lighting, to describe lumens per watt; the correct term is efficacy. See efficacy. Electric Discharge The passage of an electric current through gases and vapors. This results in the emission of electromagnetic radiation (light). Electromagnetic Spectrum A continuum of electric and magnetic radiation that can be characterized by wavelength or frequency. Visable light encompasses a small part of the electromagnetic spectrum in the region from about 380 nanometers (violet) to 770 nanometers (red) by wavelength. Electronic Ballast A short name for a fluorescent high frequency electronic ballast. Electronic ballasts use a solid state electronic components and typically operate fluorescent lamps at frequencies in the range of 25-35 kHz. The benefits are: increased lamp efficacy, reduced ballast losses, and lighter, smaller ballasts compared to electromagnetic ballasts. Emergency Lighting Lighting provided for use when the supply to the normal lighting fails. Energy Policy Act (EPACT) Comprehensive energy legislation passed by the US Congress in 1992. The lighting portion includes lamp labeling and minimum energy efficacy (lumens/watt) requirements for many commonly used incandescent and fluorescent lamp types. Similar legislation is being proposed in Canada. Escape Lighting That part of the emergency lighting provided to ensure that an escape route can be effectively identified and used in case of failure of the normal lighting system. Federal Communications Commission A US Federal Agency which is charged with regulating emissions in the radio frequency portion of the electromagnetic spectrum. For example, a regulation entitled, "Part 18" deals with electromagnetic interference (EMI) from all lighting devices operating at frequencies higher than 9 kilohertz (kHz). Typical electronically-ballasted compact fluorescent lamps operate in the range of 24-100 kHz. Flicker Impression of fluctuating brightness or color. Floodlight 1. A fixture designed for floodlighting, usually capable of being pointed in any direction and of weatherpoof construction. 2. A lamp with a wide beam of light usually greater than 20 beam spread. Fluorescent Lamp Discharge lamp of the low-pressure mercury type in which most of the light is emitted by a layer of fluorescent material excited by the ultraviolet radiation from the discharge. For example: F40T12. Footcandle (FC) The amount of lumens falling on an area measured in square feet. One lumen falling on one square foot is equal to one footcandle. Full Spectrum Lighting There is no official definition of the term "full spectrum" but most agree that it is a source that has a cool temperature and a high color rendering that mimics natural daylight. Philips Colortone 50 or C50 is described as a full spectrum light source. Fuse Safety device to prevent excess current flow. General Lighting Substantially uniform lighting of an area, excluding task lighting. Glare Condition of vision in which there is discomfort or a reduction in the ablity to see significant objects, or both, due to an unsuitable distribution or amount of light. Group Relamping An economical method to predict bulb life and replace all lamps at one time. Saves time and money. Halogen Lamp Gas-filled lamp containing a tungsten filament and a proportion of halogen gas. The halogen gas recycles evaporated particles of tungsten back onto the filament surface. Heat Measured in British Thermal Units (BTUs). Unit BTUs per hour = Watts x 3.413 High Intensity Discharge Lamps (HID) HID lamps include groups of lamps known as Mercury Vapor, Metal Halide, and High Pressure Sodium. High Pressure Mercury (Vapor) Lamp A long life lamp, with or without a coating of phosphor, in which an arc flowing through mercury vapor produces a bluish-white light. Deluxe phosphor coated lamps have a higher CRI. High Pressure Sodium Lamps (HPS) A high efficiency and long life bulb in which an arc flowing through sodium vapor produces a yellow light. Hot Re-Strike Time In HID lamps, the amount of time after a momentary power interruption to return of full light output. Ranges from 1-15 minutes or more, depending on lamp type and fixture. Illuminance (E) At a point on a surface. The amount of light striking a surface. Unit footcandle, fc in USA, lux, lx. in Europe. The orientation of the surface may be defined, e.g., horizontal, vertical, hence horizontal illuminance, vertical illuminance. Illumination Application of light to a scene, objects or their surroundings so that they may be seen. Incandescent (electric) Lamp Lamp in which light is produced by heating a filament to incandescence by the passage of an electric current. Indirect Light On a surface. The light received by the surface from a lighting installation after reflection from other surfaces. Indirect Lighting Lighting by means of fixtures or luminaires that have 90-100 percent of the light reaching the working plane indirectly or reflected from the ceiling or walls. Infrared Radiation Long wavelengths of energy, that heat objects instantly. Instant-start Lamp Fluorescent lamp designed to start without reheating of the electrodes. Usually has a single pin and starts instantly. Intensity (I) Of a source in a given direction. Used mainly in directional light sources; the strength of the beam. Unit candela, cd. Inverse Square Law The law that states that the amount of light striking a surface varies directly with the intesity of the source and inversely as the square of the distance between the sources and the surface. FC + CP/D2 Kilowatt (Kw) A measure of electrical power equal to 1000 watts. Kilowatt-Hour (KwH) Unit of electrical power consumed over a period of time. One thousand watts used for one hour equals one kilowatt-hour. KwH = Watts/1000 x hours used. Lamp An artificial source of light commonly referred to as a bulb. Also portable luminaire equippedwith a cord and a plug. Lamp Mortality See Mortality Rate. Light Any radiation capable of causing a visual sensation direct, i.e., visable radiation. Light Output Amount of light produced by a light source such as a lamp. Measured in lumens or candlepower. Lighting (or illumination) Application of light to a scene, objects, or their surroundings as that they may be seen. Louvre Shield made of translucent or opaque material and positioned to prevent lamps from being directly visible over a given angle. Low Pressure Sodium Lamp (LPS) The most efficient man made light source. LPS only produces yellow light therfore it has a 0 CRI. Example: A SOX lamp. Lumen The unit of measure for the total amount of light from a light source, regardless of direction. Unit lumen, L. Luminaire A fixture or apparatus that distributes, filters, or transforms the light given by a lamp or lamps which includes all the items necessary for fixing and protecting these lamps and for connecting them to the supply circuit. Luminance (L) In a given direction, the amount of light coming off of the surface. Unit candela per square foot, cd/ft2. Lux (FC) The metric unit of illuminance. The amount of lumens falling on an area measured in square meters. One lumen falling on one square meter in equal to one lux. Maximum Beam Candlepower (MBCP) The maximum intensity of the beam in a given direction. Usually in the center of the beam. Unit candela, cd. Metal Halide Lamp Discharge lamp that produces a white light with good color rendering and high efficiency. M.O.L. The maximum overall length of a lamp from the tip of the base to the top of the glass. Mortality Rate The number of operating hours elapsed before a certain percentage of the lamps fail. Mountain Height The distance between fixtures and the working plane. Operating Current Current in amps consumed by a lamp at rated watts. Operating Voltage Voltage at rated watts after a lamp fully warms. PAR Lamps Parabolic Aluminized Reflector lamps which offer excellent beam control, come in a variety of beam patterns from spot to flood, and can be used outdoors unprotected because they are made of "hard" glass that can withstand adverse weathre. Parabolic A concave mirror, the reflecting surface of which has the shape of a paraboloid, capable of focusing rays parallel to its axis to a point. Peak Intensity The luminous intensity of a luminaire or lamp in the direction of the beam axis. Pendent (Pendant) Luminaire Luminaire provided with a cord, chain, tube, etc. which enables it to be suspended from a ceiling or other support. Point Source A source of light in which the dimensions are small, compared with the distance between the source and the working surface. Produces sharp shadows. Power Factor Power factor in lighting is primarily applicable to ballasts. It is the ration of watts over volts multiplied by amperes. Since volts and watts are fixed, amperes (the current) will go up as the power factor goes down. This necessitates the use of larger wire sizes to carry the increased amount of current needed with low power factor ballasts as compared to high power factor ballasts. Preheat Fluorescent Lamp A fluorescent lamp designed for operation on a circuit requiring a manual starting switch or a starter to preheat the electrodes in order to start the arc. QL Induction Lamp (System) A super long life lamp (system), based on the low-pressure mercury discharge principle but without electrodes, in which the ionization of the gas within a discharge vessel is brought about by the induction of high-frequency electromagnetic field. Philips QL System file = 100,000 hours. R lamps Reflectorized lamps available in spot (clear face) and flood (frosted face). Radiation Emission or transfer of energy in the form of electromagnetic waves or particles. Rapid Start Fluorescent Lamp A fluorescent lamp designed for operation with a ballast that provides a low-voltage winding for preheating the electrodes and initiating the arc without a starter or the application of high voltage. Takes about one second to start. Recessed Luminaire Luminaire mounted above the ceiling or behind a wall or other surface so that any visible projection is insignificant. Reflectance Ration of the reflected light to the incident light on a surface. Reflected Glare Glare resulting from reflections of high brightness sources in polished or glossy surfaces in the field of view. Reflection Light striking a surface is either absorbed, transmitted, or reflected. Reflected light is that which bounces off the surface, and it can be classified as specular or diffuse reflection. Specular reflection is characterized by light rays which strike and leave surface at equal angles. Diffuse reflection leaves a surface in all directions. Reflector Device in which the phenomenon of reflection is used to alter the distribution of the light source. Reflector Lamp Lamp in which part of the bulb is coated with a reflecting material, either diffuse or specular, so as to contorl the light. Example: R, BR, PAR bulbs. Re-strike Time The time it takes for a lamp to re-strike after a power interruption. In most HID lamps, if the lamp is at full brightness and the power is removed for even a split second, the lamp will extinguish and will have to cool down before it re-strikes, which can take between 1-15 minutes depending on lamp type, wattage and fixture variables. Retina Membrane at the back of the eye which is sensitive to light stimuli and containing photreceptors (cones and rods) and nerve cells that transmit the stimulation to the optic nerve. Rod Photoreceptors in the retinal containing light-sensitive pigments. Rods probably play no part in color discrimination. Rough Service Lamps Incandescent lamps designed with extra filament supports to withstand bumps, shocks, and vibrations. SAD Seasonal Affective Disorder is a type of depression, a feeling of lethargy, that may be related to the reduction of sunlight as days grow shorter. Also known as "Winter Time Blues" or "Cabin Fever". It is sometimes treated with "Full Spectrum" lighting. Shielding An arrangement of light-controlling material to prevent direct view of the light source. Spacing The distance between the centers of two successive luminaires in an installation. Spacing to Mountain Height Ratio (S/M) The ratio of the distance between luminaire centers to the height above the work plane. Gives the maximum spacing of luminaires at which even illumination will be provided. Speed of Light Approximately 186,000 miles per second. Spill Light The scattered light of a floodlight falling outside the beam that is usually considered wasted light. Spotlight A (small) projector giving concentrated light usually not more than 20 beam spread. Stand-by Lighting That part of emergency lighting that enables normal activities to continue substantially unchanged. Starter Device for starting a fluorescent lamp that provides for the necessary preheating of the electrodes and/or causes a voltage surge in combination with the series ballast. Task Lighting Lighting for a specific visual task, additional to and controlled separately from the general lighting. The term is often applied to lighting designed to illunimate a particularly small area, e.g. a desk top. TCLP Toxic Characteristic Leaching Procedure A US Environmental Protection Agency test for non-hazardous waste, a test designed to measure substances that might dissolve into the ecosystem. Philips ALTO lamps pass this test. Transformer Device used to raise or lower voltage to a lamp. Transmission Passage of light through a material. Troffer A long, recessed luminaire usually installed with the opening flush with the ceiling. Tungsten-Halogen Lamp A gas filled incandescent lamp with a tungsten filament containing a certain proportion of halogens (usually bromine). Ultraviolet Radiation Invisible radiation in which the wavelengths are shorter than those for visible radiation. Uniformity A measure of the variation of light over a given area expressed as either: 1. The ratio of the minimum to the maximum illuminance, 2. The ratio of the minimum to the average illuminance. Valance Lighting Lighting system comprising light sources shielded by a panel parallel to the wall at the top of a window. Visible Radiation Any radiation capable of causing a visual sensation directly. Visual System The group of structures comprising the eye, the optic nerve, and certain parts of the brain, which is responsible for seeing. Warm-up Time The amount of time from turn-on to 90% light output. Watt (W) The unit for measuring power. W= VxA Wavelength Distance of a periodic wave between two successive points at which the phase is the same. Unit meter, m. Ultraviolet (UV) Radiation Radiant energy in the range of about 100-380 nanometers (nm). For practical applications, the UV band is broken down further as follows: Underwriter Laboratories (UL) A private organization which tests and lists electrical (and other) equipment for electrical and fire safety according to recognized UL and other standards. A UL listing is not an indication of overall performance. Lamps are not UL listed except for integrated compact fluorescent lamps - those with screw bases and built-in ballasts. Volt (V) The unit for measuring electric potential. It defines the force or pressure of electricity. WISO With Industry Superior Optics. A segmented parabolic reflector designed specifically for an axially mounted halogen capsule. Produces an extremely smooth, round beam with high efficiency. See picture on page 5. Work (or working) Plane Reference surface defined as the plane at which work is usually done. Example: The table top is the working plane. Zenith The direction directly above the luminaire. |
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