Definitions of Common Lighting Terms

ABCDEFGHIJKLMNOPQRSTUVWXYZ

OHM
Operating Position

PAR Lamp
Phosphor
Power Factor (PF)
Preheat Circuit

Proforma Invoice

Quartz-Halogen

Rapid Start Circuit
Rated Lamp Life
Reflector Lamp (R)
ROHS

Scotopic/Photopic (S/P) Ratio
Sealed Beam Lamp
Single Ended Lamp
Skirted Base
Spectral Power Distribution (SPD)

TAL
TCLP Test
Teflon
Total Harmonic Distortion (THD)

Ultraviolet (UV) Radiation
Underwriters Laboratories (UL)

Veiling Reflections
Visual Comfort Probability
Voltage

Watt

Xenon Lamp

Yard Lighting

Zone Lighting

Ambient Lighting

The general lighting present in an area--excluding task lighting and accent lighting but including general lighting and daylight streaming in.

American National Standards Institute (ANSI) Previously ASI

A consensus-based organization which coordinates voluntary standards for the physical, electrical and performance characteristics of lamps, ballasts, luminaires and other lighting and electrical equipment.

Amperes

("Amps") A measure of electrical current. In incandescent lamps, the current is related to voltage and power as follows: Current (Amps) = Power (Watts) / Voltage (Volts).

ANSI Code

A three letter system that has been devised to describe lamps of different manufacture but the same application. The letters have no relationship to lamp description, but the same letters always designate the same type of lamp. Some of the application parameters they define are wattage, base type, envelope size, maximum overall length, maximum overall diameter and light center length.

Aperture

In optics, an aperture is a hole or an opening through which light is admitted. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane.

Arc

The light caused by an electrical discharge between two electrodes in a gas such as xenon, argon, or air. The first usable arc as a practical light source was developed in 1809 by Sir Humphrey Davy.

Ballast

An auxiliary piece of equipment required to start and to properly control the flow of current to gas discharge light sources such as fluorescent and high intensity discharge (HID) lamps.

Ballast Factor (BF)

This is the percentage of a lamp's rated lumen output that can be expected when operated on a specific, commercially available ballast. For example, a ballast with a ballast factor of 9.93 will result in the lamp's emitting 93% of its rated lumen output. A ballast with a lower BF results in less light output and also generally consumes less power.

Beam Angle

The angular dimension of the cone of light from reflectorized lamps (such as R, BR, AR and PAR types) encompassing the central part of the beam out to the angle where the intensity is 50% of maximum. The beam angle sometimes called "beam spread" is often part of the ordering code for reflectorized lamps. Example: The 50PAR30/HIR/NFL25 is a 50 watt PAR30 narrow flood lamp with a beam angle of 25 degrees. See also Field Angle.

Beam Pattern

The complete shape of the beam, as defined in the general sense. It includes any realistic or abstract patterns introduced into the beam as well as any apparatus that alters the contour of the beam.

Blacklight

A luminaire with a beam whose wavelengths are too short to be visible, i.e., 320 to 380 nm. These ultraviolet wavelengths excite fluorescent materials, paints, etc., in theatrical applications.

Burn Position

Operating Position: For good performance, lamps must be used within specified limitations on operating position. Lamps with plane or flat mandril filaments should only be inclined perpendicular to the filament plane. The following abbreviations are used in the lamp descriptions to indicate these limits:

BD=Base Down. Operate Only Vertical, Base Down
BU=Base Up. Burn Only With the Base Up.
H15=Base Up ±15°
H30=Base Up ±30°
H105=Base Up ±105°
H22=Operate Base Down to 22° Base Up.
HD=Base Down to Horizontal. Do Not Operated Base Above Horizontal
P4=Horizontal ±4°
P15=Horizontal ±15°
P20=Horizontal ±20°
P30=Horizontal ±30°
P45=Horizontal ±45°
P90/15=Horizontal ±105°
S10=Base Down ±10°
S15=Base Down ±15°
S15/P15=Base Down ±15° or Burn Horizontal ±15°
S20=Base Down ±20°
S20/P20=Base Down ±20° or Burn Horizontal ±20°
S30=Base Down ±30°
S30/P30=Base Down ±30° or Burn Horizontal ±30°
S30/P20=Base Down ±30° or Burn Horizontal ±20°
S45=Base Down ±45°
S100=Base Down ±100°
S105=Base Down ±105°
S120=Base Down ±120°
S135=Base Down ±135°
S90=Base Down ±90°
U=Universal. Operate In Any Position
VBU=Vertical Bulb Up-Base Down

Candela (cd)

The measure of luminous intensity of a source 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 defined as producing one candela in every direction. A plot of intensity versus direction is called a candela distribution curve and is often provided for reflectorized lamps and for luminaires with a lamp operating in them.

Candlepower

An obsolete term for luminous intensity; current practice is to refer to this simply as candelas. See Candela.

Center Beam Candlepower (CBCP)

Refers to the luminous intensity at the center of the beam of a blown or pressed reflector lamp (such as a PAR lamp). Measured in candelas. See also Candela. Also know as MSCP.

Ceramic Metal Halide (CHM®)

A Type of metal halide lamp that uses a ceramic material for the arc tube instead of glass quartz, resulting in better color rendering (>80 CRI) and improved lumen maintenance.

CIM

Construction and Industrial Machinery. CIM is a term for lamps designed for construction and industrial machinery applications.

Coefficient of Utilization

In general lighting calculations, the fraction of initial lamp lumens that reach the work plane. CU is a function of luminaire efficiency, room surface reflectances and room shape.

Cold Start

A term used to describe the ignition of a cold arc lamp, i.e., a lamp that has not been electrified for a relatively long period of time.

Color Rendering Index (CRI)

An international system used to rate a lamp's ability to render object colors. The higher the CRI (based upon a 0-100 scale) the richer colors generally appear. CRI ratings of various lamps may be compared, but a numerical comparison is only valid if the lamps are close in color temperature. CRI differences among lamps are not usually significant (visual to the eye) unless the difference is more than 3-5 points.

Color Temperature (Correlated Color Temperature - CCT)

A number indicating the degree of "yellowness" or "blueness" of a white light source. Measured in Kelvins, CCT represents the temperature an incandescent object (like a filament) must reach to mimic the color of the lamp. Yellowish-white ("warm") sources, like incandescent lamps, have lower color temperatures in the 2700K - 3000K range; white and bluish-white ("cool") sources, such as cool white (4100K) and natural daylight (6500K), have higher color temperatures. The higher the color temperature the whiter, or bluer, the light will be.

Compact Fluorescent Lamp (CFL)

The general term applied to fluorescent lamps that are single-ended and that have smaller diameter tubes that are bent to form a compact shape. Some CFLs have integral ballasts and medium or candelabra screw bases for easy replacement of incandescent lamps. Compact fluorescent lamp electrical savings are significant. If you pay 10¢ per KWH for your electricity and the typical compact fluorescent lamp lasts for 10,000 hours the electrical cost for a 27W compact fluorescent lamp is $27.00 over the life of the lamp. (27W x 10,000H=270,000W/H=270KWH x 10¢ = $27.00). The light output of a 27W lamp is approximately equivalent to a 100W standard household incandescent lamp. To equal the compact fluorescent lamp for life you would have to buy ten 1,000 hour light bulbs and it would cost $100.00 for the electricity. The compact fluorescent lamp saves $72.00 in electricity over the life of the lamp. One disadvantage of the self ballasted compact fluorescent lamps is that they are not dimmable.

Daylight Harvesting

Lighting design for building interiors that makes use of daylight as a way of reducing energy consumption.

Daylight Lamp

A lamp resembling the color of daylight, typically with a color temperature of 5000°K to 6500°K.

DC Voltage

An electric current flowing in one direction only and substantially constant in value. Electricity from a battery is direct current.

Devitrify

To cause a glassy material to become crystalline and brittle and/or opaque. Fingerprints or grease on the surface of quartz lamps may cause devitrification of the quartz. It is recommended that glass surfaces that are subjected to high heat be free of oil and grease. Devitrification is the act or process of devitrifying, or the state of being devitrified. Specifically, the conversion of molten glassy matter into a stony mass by slow cooling, the result being the formation of crystallites, microbites, etc., in the glassy base, which are then called devitrification products.

Diamond Precise®

Diamond Precise is the GE trade name for its line-voltage MR16 ConstantColor®halogen lamp. An integral ballast and a medium screw base enable Diamond Precise lamps to operate on standard (120 volt) circuits. The MR16 technology of Diamond Precise allows a tighter, more intense beam than can be attained by the 50-watt PAR20 and R20 types it's designed to replace, even though the lumen output is significantly less by comparison.

Dichroic Reflector (or Filter)

A reflector (or filter) that reflects one region of the spectrum while allowing the other region(s) to pass through. A reflector lamp with a dichroic reflector will have a "cool beam" i.e. most of the heat has been removed from the beam by allowing it to pass through the reflector while the light has been reflected.

Dimmable

Whether or not the lamp lumens can be varied while maintaining reliability.

Dimmer, Dimming Control

A device used to lower the light output of a source, usually by reducing the wattage it is being operated at. Dimming controls are increasing in popularity as energy conserving devices.

Distance Between Legs

For U-shaped Fluorescent lamps, this measurement is the average distance between the inner walls of the legs.

Distance Between Leg Centers

For U-shaped Fluorescent lamps, this measurement is the average distance between the centers of each leg.

Distance Outside Legs

For U-shaped Fluorescent lamps, this measurement is the average distance to the outside of each leg.

Department of Transportation (DOT) Type

The US Department of Transportation lamp number stamped in the glass lens or on the base of headlamps.

DLP

Digital Light Processing Technology. DLP is a technology used in projectors and video projectors. It was originally developed at Texas Instruments, in 1987 by Dr. Larry Hornbeck. In DLP projectors, the image is created by microscopically small mirrors laid out in a matrix on a semiconductor chip, known as a Digital Micromirror Device (DMD). Each mirror represents one pixel in the projected image. The number of mirrors corresponds to the resolution of the projected image. 800x600, 1024x768, 1280x720, and 1920x1080 (HDTV) matrices are some common DMD sizes. These mirrors can be repositioned rapidly to reflect light either through the lens or on to a heatsink (called a light dump in Barco terminology). The rapid repositioning of the mirrors (essentially switching between 'on' and 'off') allows the DMD to vary the intensity of the light being reflected out through the lens, creating shades of grey in addition to white (mirror in 'on' position) and black (mirror in 'off' position).

Electrodeless lamps

Light sources where the discharge occurs in a chamber with no electrodes (no metal.) The energy for the discharge is supplied by radio frequency excitation, e.g. microwaves (See GENURA).

Electromagnetic Spectrum

A continuum of electric and magnetic radiation that can be characterized by wavelength or frequency. Visible 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 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. Electronic ballasts may also be used with HID lamps.

Elliptical Reflector (ER) Lamp

An incandescent lamp with a built-in elliptically-shaped reflecting surface. This shape produces a focal point directly in front of the lamp which reduces light absorption in some types of luminaires. It is particularly effective at increasing the efficiency of baffled downlights. The shape is rounded like an egg.

Field Angle

The angular dimension of the cone of light from reflectorized lamps (such as R and PAR types) encompassing the central part of the beam out to the angle where the intensity is 10% of maximum.

Filament

The wire inside an incandescent lamp envelope that glows and emits light when heated, i.e., when electricity passes through it. Filaments are designated by a letter combination in which C is a coiled wire filament, CC is a coiled wire that is itself wound into a larger coil, and SR is a straight ribbon filament. Numbers represent the type of filament-support arrangement.

Fixture Requirements

Describes fixture requirements for HID lamps.
O = Open or Enclosed Fixtures
E = Enclosed Fixtures Only
S = Lamps operated in a vertical position (Base Up or Down) ±15º, can be used in an open fixture. Lamps burned in any other orientation must be used in "enclosed fixtures only."

Fluorescent Lamp

A high efficiency lamp utilizing an electric discharge through low pressure mercury vapor to produce ultra-violet (UV) energy. The UV excites phosphor materials applied as a thin layer on the inside of a glass tube which makes up the structure of the lamp. The phosphors transform the UV to visible light.

Footcandle (FC)

A unit of illuminance or light falling onto a surface. It stands for the light level on a surface one foot from a standard candle. One footcandle is equal to one lumen per square foot. See also Lux.

Full Spectrum Lighting

A marketing term, typically associated with light sources that are similar to some forms of natural daylight (5000K and above, 90+ CRI), but sometimes more broadly used for lamps that have a smooth and continuous color spectrum.

Genura®

GE's electrodeless compact fluorescent lamp, Genura, uses induction to power the discharge. The chamber generates UV (just like a discharge in a regular fluorescent lamp) that is converted by phosphors to visible light. Because Genura uses no electrodes, the life of this unique reflector lamp is longer than typical compact fluorescent products (See Electrodeless lamps).

Germicidal Lamp

A lamp that kills germs, especially pathogenic microorganisms, like a disinfectant using 254nm ultraviolet radiation preventing infection by inhibiting the growth or action of microorganisms. Ultraviolet radiation UV-C is harmful to the skin and the eyes and can cause serious skin burns and eye injury either from direct or reflected radiation. To reduce the risk of personal injury, install only in a fixture which provides adequate protection to area occupants. These lamps SHOULD NOT BE USED FOR ILLUMINATION PURPOSES. You can find more details on our Germicidal Safety Sheet.

Glare

Visual discomfort caused by excessive brightness is called discomfort glare. If task performance is affected it is called disability glare. Glare can be direct glare or indirect (reflected) glare (See Veiling Reflections and Visual Comfort Probability).

Halogen Lamp

A halogen lamp is an incandescent lamp with a filament that is surrounded by halogen gases, such as iodine or bromine. Halogen gases allow the filaments to be operated at higher temperatures and higher efficacies. The halogen participates in a tungsten transport cycle, returning tungsten to the filament and prolonging lamp life.

High-Intensity Discharge (HID) Lamp

A general term for mercury, metal halide and high-pressure sodium lamps. HID lamps contain compact arc tubes which enclose various gases and metal salts operating at relatively high pressures and temperatures.

High-Pressure Sodium (HPS) Lamp

HPS lamps are high intensity discharge light sources that produce light by an electrical discharge through sodium vapor operating at relatively high pressures and temperatures.

Hot Restrike

A term applied to an ignitor that will hot start an arc lamp.  Hot restriking is the restriking of the arc in an HID light source after a momentary power loss; the lamp restarts when the arc tube has cooled sufficiently. The restrike time is dependent on the fixture application as to how long it takes the lamp to cool down to the point of restarting. This could be anywhere from 5 minutes to 20 minutes or so.

Illuminance

The ""density"" of light (lumens/area) incident on a surface; i.e. the light level on a surface. Illuminance is measured in footcandles for lux.

Incandescent Lamp

A light source that generates light utilizing a thin filament wire (usually of tungsten) heated to white heat by an electric current passing through it.

Induction Lighting

Gases can be excited directly by radio-frequency or microwaves from a coil that creates induced electromagnetic fields. This is called induction lighting and it differs from a conventional discharge, which uses electrodes to carry current into the arc. Induction lamps have no electrodes inside the chamber and generally, therefore, have longer life than standard lamps.

Infrared Radiation

Electromagnetic energy radiated in the wavelength range of about 770 to 1,000,000 nanometers. Energy in this range cannot be seen by the human eye, but can be sensed as heat by the skin.

Instant Start

A type of ballast designed to start fluorescent lamps as soon as the power is applied. Most T8 fluorescent lamps are being operated on electronic instant-start ballasts. Slimline fluorescent lamps operate only on instant start circuits.

Joule

The International System unit of electrical, mechanical, and thermal energy. A unit of electrical energy equal to the work done when a current of one ampere is passed through a resistance of one ohm for one second.  A unit of energy equal to the work done when a force of one newton acts through a distance of one meter.

Kilowatt (kW)

A measure of electrical power equal to 1000 watts.

Kilowatt Hour (kWh)

The standard measure of electrical energy and the typical billing unit used by electrical utilities for electricity use. A 100-watt lamp operated for 10 hours consumes 1000 watt-hours (100 x 10) or one kilowatt-hour. If the utility charges $.10/kWh, then the electricity cost for the 10 hours of operation would be 10 cents (1 x $.10).

Lamp

The term used to refer to the complete light source package, including the inner parts as well as the outer bulb or tube. "Lamp", of course, is also commonly used to refer to a type of small light fixture such as a table lamp.

Lampholder

The electrical device that supports a lamp in a luminaire, and generally contains the contacts that make the electrical connection to the contacts of the lamp base.

LCD

Liquid-Crystal Display: a method of displaying readings continuously, as on digital watches, portable computers, and calculators, using a liquid-crystal film, sealed between glass plates, that changes its optical properties when a voltage is applied. LCD (liquid crystal display) projectors usually contain three separate LCD panels, one each for the red, green, and blue components of the video signal. However single panel LCD projectors have been produced in the past. Light from a lamp is split by a prism into the three component colors. These lamps also have the ability to produce an extremely large amount of light within a small area, on average for current projectors of 2,000-4,000 ANSI Lumens. As light passes through the LCD panels, individual pixels can be opened to allow light to pass, or closed to block the light, as if each little pixel were fitted with a Venetian blind. This activity modulates the light and produces the image that is projected onto the screen by allowing many different shades from each color LCD panel.

LED

Light-Emitting Diode: a semiconductor diode that emits light when conducting current and is used in electronic equipment. The semiconductor diode converts applied voltage to light and is used in digital displays such as calculator, digital watch, etc.

Life

See Rated Lamp Life.

Light

Radiant energy that can be sensed or seen by the human eye. Visible light is measured in lumens.

Light Center Length (L.C.L.)

The distance between the center of the filament, or arc tube, and a reference plane - usually the bottom of the lamp base.

Lumen

A measure of luminous flux or quantity of light emitted by a source. For example, a dinner candle provides about 12 lumens. A 60-watt Soft White incandescent lamp provides 840 lumens. Electric Light Inside.

Lumen Maintenance

A measure of how well a lamp maintains its light output over time. It may be expressed numerically or as a graph of light output vs. time.

Luminaire

A complete lighting unit consisting of a lamp (or lamps), ballast (or ballasts) as required together with the parts designed to distribute the light, position and protect the lamps and connect them to the power supply. A luminaire is often referred to as a fixture.

Luminance

A photometric measure of "brightness" of a surface as seen by the observer, measured in candelas per square meter.

Luminare Efficiency

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

Luminous Efficacy

The light output (lumens) of a light source divided by the total power input (watts) to that source. It is expressed in lumens per watt.

Lux (lx)

A unit of illuminance or light falling onto a surface. One lux is equal to one lumen per square meter. Ten lux approximately equals one footcandle. See also Footcandle. This is often referred to as center beam candle power or CBCP.

Mandril

 A metal rod or bar around which material, such as metal or glass, may be shaped.

Maximum Overall Length (M.O.L.)

The end-to-end measurement of a lamp, expressed in inches or millimeters.

Mean Lumens

The average light output of a lamp over its rated life. Based on the shape of the lumen depreciation curve, for fluorescent and metal halide lamps, mean lumens are measured at 40% of rated lamp life. For mercury, high pressure sodium and incandescent lamps, mean lumen ratings refer to lumens at 50% of rated lamp life. See Lumen Maintenance. Or possibly lumens that are not very nice, I am not sure which.

Mercury Lamp

A high-intensity discharge light source operating at a relatively high pressure (about 1 atmosphere) and temperature in which most of the light is produced by radiation from excited mercury vapor. Phosphor coatings on some lamp types add additional light and improve color rendering.

Metal Halide Lamp

A high-intensity discharge light source in which the light is produced by the radiation from mercury, plus halides of metals such as sodium, scandium, indiu, and dysprosium. Some lamp types may also utilize phosphor coatings.

Micrometric

Relating to or made by a micrometer. Micrometry is the measurement of minute objects with a micrometer. A micrometer is a device for measuring very small distances, objects, or angles, especially one based on the rotation of a finely threaded screw, as in relation to a microscope.

Nanometer

A unit of wavelength equal to one billionth of a meter.

OHM

A unit of electrical resistance equal to that of a conductor in which a current of one ampere is produced by a potential of one volt across its terminals. A unit of electrical resistance equal to the resistance between two points on a conductor when a potential difference of one volt between them produces a current of one ampere.

PAR Lamp

PAR is an acronym for parabolic aluminized reflector. A PAR lamp, which may utilize either an incandescent filament, a halogen filament tube or a HID arc tube, in a precision pressed-glass reflector lamp. PAR lamps rely on both the internal reflector and prisms in the lens for the control of the light beam.

Phosphor

An inorganic chemical compound processed into a powder and deposited on the inner glass surface of fluorescent tubes and some mercury and metal-halide lamp bulbs. Phosphors are designed to absorb short wavelength ultraviolet radiation and to transform and emit it as visible light.

Power Factor (PF)

A measure of the phase difference between voltage and current drawn by an electrical device, such as a ballast or motor. Power factors can range from 0 to 1.0 with 1.0 being ideal. Power factor is sometimes expressed as a percent. Incandescent lamps have power factors close to 1.0 because they are simple "resistive" loads. The power factor of a fluorescent and HID lamp system is determined by the ballast used. "High" power factor usually means a rating of 0.9 or greater. Power companies may penalize users for using low power factor devices.

Preheat Circuit

A type of fluorescent lamp-ballast circuit used with the first commercial fluorescent lamp products. A push button or automatic switch is used to preheat the lamp cathodes to a glow state. Starting the lamp can then be accomplished using simple "choke" or reactor ballasts.

Proforma Invoice

A quotation in the form of an invoice prepared by the seller that details items which would appear on a commercial invoice if an order results. An invoice sent in advance of shipment, usually to enable the buyer to obtain an import permit or foreign exchange permit, or both. The proforma invoice gives a close approximation of the weights and values of the shipment to be made.

Quartz-Halogen

Quartz is a very hard crystalline form of silicon dioxide used in chemical apparatus and in optical and electric instruments. Quartz is used to make a colorless glass made of almost pure silica. A clear vitreous solid, formed by melting pure quartz, that can withstand high temperatures and is extremely transparent to infrared, visible, and ultraviolet radiations. Also called fused quartz or fused silica. Quartz glass is often combined with halogen gas for smaller lamps that withstand higher heat.  A halogen lamp is an incandescent lamp with a filament that is surrounded by halogen gases, such as iodine or bromine. Halogen gases allow the filaments to be operated at higher temperatures and higher efficacies. The halogen participates in a tungsten transport cycle, returning tungsten to the filament and prolonging lamp life.

Rapid Start Circuit

A fluorescent lamp-ballast circuit that utilizes continuous cathode heating, while the system is energized, to start and maintain lamp light output at efficient levels. Rapid start ballasts may be either electromagnetic, electronic or of hybrid design. Full-range fluorescent lamp dimming is only possible with rapid start systems.

Rated Lamp Life

For most lamp types, rated lamp life is the length of time of a statistically large sample between first use and the point when 50% of the lamps have died. It is possible to define "useful life" of a lamp based on practical considerations involving lumen depreciation and color shift. The average rated life for a lamp is calculated by burning a group of lamps at the perfect rated voltage. The point at which half of the lamps are out and half are burning is the average rated life. Your actual life will vary greatly based on how you use the lamp. Lamp handling, voltage applied, use cycles and environment are all factors that alter your actual lamp life. Generally, manufacturers only warranty against defects in manufacturing.

Reflector Lamp (R)

A light source with a built-in reflecting surface. Sometimes, the term is used to refer specifically to blown bulbs like the "R" and "ER" lamps; at other times, it includes all reflectorized lamps like PAR and MR.

ROHS

The RoHS Directive stands for "the restriction of the use of certain hazardous substances in electrical and electronic equipment".  This Directive bans the placing on the EU market of new electrical and electronic equipment containing more than agreed levels of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants.

Scotopic/Photopic (S/P) Ratio

This measurement accounts for the fact that of the two light sensors in the retina, rods are more sensitive to blue light (Scotopic vision) and cones to yellow light (Photopic vision). The Scotopic/Photopic (S/P) Ratio is an attempt to capture the relative strengths of these two responses. S/P is calculated as the ratio of scotopic lumens to photopic lumens for the light source on an ANSI reference ballast. Cooler sources (higher color temperatures lamps) tend to have higher values of the S/P Ratio compared to warm sources.

Sealed Beam Lamp

A lamp with an integral light source, reflector, and lens, all of which are either sealed within, or are a part of the envelope.

Single Ended Lamp

A lamp that has only one base and all of its contacts on the base.

Skirted Base

A protective sleeve that extends beyond the base of the lamp over the glass of the lamp. The purpose of the skirt is to provide more holding area to better attach the lamp to the base. This is important in some base up operations where a lot of heat can affect the ceramics attaching to the base and glass. Skirting can also help support heavier glass styles like PAR lamps for example. Modern ceramics withstand more heat and so skirting is less important with newer lamps.

Spectral Power Distribution (SPD)

A graph of the radiant power emitted by a light source as a function of wavelength. SPD's provide a visual profile of "finger print" of the color characteristics of the source throughout the visible part of the spectrum.

TAL (Turn and Lock)

TAL lamps have a twin post base that you insert and turn to lock into position. These are sometimes also referred to as Twist and Lock type lamps. These MR16 halogen dichroic lamps have a cover glass and a varitey of beam spreads. The following chart shows the lamp options available. The narrow beam lamps have a trapezoidal faceted mirror reflector and these include the 414, 417, 420 and 424. The remainder of the medium and wide flood beam spreads have honeycomb mirror reflectors

Lamp	Wattage	Beam Angle	Lux at 1M	Lux at 2M	Lux at 3M	Lux at 4M	Lux at 5M
TAL414	20W	11°	4500	1125	500	282	180
TAL415	20W	24°	900	225	100	57	36
TAL416	20W	36°	450	113	50	28	18
TAL417	35W	8°	8100	2025	900	504	324
TAL418	35W	18°	3240	810	360	203	130
TAL419	35W	38°	873	219	97	55	35
TAL420	50W	10°	10800	2700	1270	675	432
TAL421	50W	21°	3330	833	370	208	133
TAL422	50W	38°	1395	349	155	87	56
TAL423	50W	60°	630	158	70	40	25
TAL424	65W	12°	12960	3240	1440	810	518
TAL425	65W	18°	6075	1518	675	380	243
TAL426	65W	38°	1822	455	202	113	72

TCLP Test

The Toxicity Characteristic Leaching Procedure (TCLP) test, specified in the Resource Conservation and Recovery Act (RCRA) of 1990, is used to characterize fluorescent lamp waste as hazardous or nonhazardous waste. The TCLP test measures the ability of the mercury and/or lead in a lamp to leach from a landfill into groudwater.

Teflon®

Teflon is a registered trademark for Dupont. Teflon is a trade name for a solid, chemically inert polymer of tetrafluoroethylene (C2F4), F2C[dbond]CF2. Stable up to temperatures around 572°F (300°C), Teflon is used in electrical insulation, gaskets, and in making low-adhesion surfaces, e.g., for nonstick cookware. In the lighting industry teflon is used to coat lamps to prevent the glass from breaking and to hold the glass together should it break. Often Teflon is used to tough coat lamps for construction applications and resists thermal shock breakage from inclement weather when water, sleet or snow come in contact with the lamp. Certain lamps like the GBF and 1383 are used in elevators with Teflon coating.. In food applications Teflon helps prevent glass from getting into food or hitting people should a lamp break.

Total Harmonic Distortion (THD)

A measure of the distortion of the input current on alternating current (AC) power systems caused by higher order harmonics of the fundamental frequency (60Hz in North America). THD is expressed in percent and may refer to individual electrical loads (such as ballast) or a total electrical circuit or system in a building. ANSI C82.77 recommends THD not exceed 32% for individual commercial electronic ballasts, although some electrical utilities may require lower THDs on some systems. Excessive THDs on electrical systems can cause efficiency losses as well as overheating and deterioration of system componenets.

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:
• Ozone-producing — 180-220nm
• Bactericidal (germicidal) — 220-300nm
• Erythemal (skin reddening) — 280-320nm
• "Black" light — 320-400nm
The International Commission on Illumination, CIE, defines the UV band as UV-A (black light) 315-400nm; UV-B 280-315nm and UV-C (germicidal) 100-280mm.

A UV-A ultraviolet black light is a lamp that emits long wave UV radiation and very little visible light. Fluorescent black lights are typically made in the same fashion as normal fluorescent lights except that only one phosphor is used and the normally clear glass envelope of the bulb may be replaced by a deep-bluish-purple nickel-oxide–doped glass which blocks almost all visible light above 400 nanometers. The color of these lamps is referred to as "blacklight blue" or "BLB." This is to distinguish these lamps from "bug zapper" blacklight ("BL") lamps that don't have the blue glass. These lamps output at 354nm.

The name ultraviolet means "beyond violet" from Latin ultra, "beyond", violet being the color of the shortest wavelengths of visible light. UV light has a shorter wavelength than that of violet light.

Underwriters 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 in not an indication of overall performance. Lamps are not UL listed except for compact fluorescent lamp assemblies - those with screw bases and built-in ballasts and LED products because of the required electrical components. UL registered products are UL Listed or UL Recognized. UL Listed means the product has been tested and meets standards. UL Recognized applies to components that meet applicable standards but they may need to be incorporated in specific ways in order to be safely used.

Veiling Reflections

Veiling reflections are specular reflections superimposed upon diffuse reflections from an object that partially or totally obscures visual details by reducing luminance contrast and therefore visibility. The facets of "glossiness" inherent in almost all objects are too small to be visible to the naked eye, although they can be seen under a suitable microscope. Nevertheless, the macroscopic effect, called reflected glare, can be experienced directly by anyone who attempts to read a glossy magazine while facing a window on a bright, sunny day. The image of the sun and sky is reflected as a veil of light directly into the observer's eyes, reducing contrast and therefore also visibility.

In practice, veiling reflections may be minimized by positioning overhead luminaires (or employing ones with appropriate intensity distributions) in such a way that most of the light passes in front of and across the observer, perpendicular to the direction in which he faces, so minimizing specular reflections in the direction of view. This can also be achieved by employing multi-layer polarizing panels in luminaires that produce vertically polarized light. Veiling reflections are one of the most important factors affecting lighting quality; a non-uniform luminance distribution surrounding the visual task is another, but less significant.

Visual Comfort Probability

A rating system for evaluating direct discomfort glare, expressed as the percent of occupants of a space who will be bothered by direct glare. VCP takes into account luminaire luminance at different angles of view, luminaire size, room size, luminaire mounting height, illuminance and room surface reflectiveness.

Voltage

A measurement of the electromotive force in an electrical circuit or device expressed in volts. Voltage can be thought of as being analogous to the pressure in a waterline. Orthodox Static Pressure

Watt

A unit of electrical power. Lamps are rated in watts to indicate the rate at which they consume energy. See Kilowatt Hour. Consuming War Potential.

Xenon Lamp

A xenon lamp is a light source containing xenon gas; often operated as a pulsed light source, as in a strobe lamp. The addition of xenon gas into the glass envelope of a lamp increases the rated life of the lamp. Depending on the lamp the average rated life is somewhere between 8,000 and 20,000 hours. Xenon lamps run cooler than the line voltage halogen lamps and xenon lamps are dimmable in non-pulsed applications. Xenon lamps have a Color Temperature that is between ordinary incandescent and halogen. That is, the light is cooler in appearance than incandescent but warmer in appearance than halogen.

Yard Lighting

Outdoor lighting fixtures, including hanging pendant lamps, wall lights, security lights and landscape lighting used to beautify and enhance an outdoor space.

Zone Lighting

In dimming, lights that are operated together. Also called Channel Lighting.

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