American National Standards Institute (ANSI)
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.
These are 3-letter codes assigned by the American National Standards Institute. They provide a system of assuring mechanical and electrical interchangeability among similarly coded lamps from various manufacturers. General Electric uses the assigned ANSI Codes as Lamp Ordering Codes for most Projection Lamps.
Also called “lighting application,” it refers to the particular use the lamp is being put to. (e.g. high-bay industrial application or retail lighting application.) The term can also refer in a general way to “application engineering” which deals with specific paramters and usage of light sources. (e.g. how to do a lighting layout, where to place fixtures and so on.)
A general term for a high intensity electrical discharge occurring between two electrodes in a gaseous medium, usually accompanied by the generation of heat and the emission of light (See ELECTRICAL DISCHARGE).
A light source containing an arc (see above). Also called a discharge lamp, or an arc discharge lamp (See ELECTRICAL DISCHARGE).
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 0.93 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.
Base or Socket
” the base is the end of the lamp that fits into the socket. There are many types of bases used in lamps, screw bases being the most common for incandescent and HID lamps, while bipin bases are common for linear fluorescent lamps. Sample Base Types
“The socket is the receptacle connected to the electrical supply
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 50% of maximum. The beam angle sometimes called “beam spread” is often part of the ordering code for the reflectorized lamps. Example: The 50PAR30/HIR/NFL25 is a 50 watt PAR30 narrow flood lamp with a beam angle of 25 degrees (See FIELD ANGLE).
Beam Spread (Approximate)
For reflector type lamps. The total angle of the directed beam (in degrees horizontal or vertical) to where the intensity of the beam falls to 50% or 10% of the maximum candlepower value as indicated.
Any base with two metal pins for electrical contact. This is the typical base for a fluorescent tube of 1 to 4 feet in length. It consists of 2 prong contacts which connect into the fixture. Medium bi-pins are used with type T-8 and T-12 tubular fluorescent lamps, and miniature bi-pins are used for tubular T-5 fluorescent lamps.
GE trademark for its biaxial family of high-efficiency and long-life compact fluorescent lamps. A straight tube is bent back in the middle, constituting a biaxial tube.
A hot body with an incandescent black surface at a certain temperature used as a standard for comparison. Note that a black surface is the best radiator possible. A tungsten filament will emit slightly less radiation than a blackbody at the same temperature.
Bulb shape followed by its size (the maximum diameter of the bulb expressed in eighths of an inch). For Compact Fluorescent products, “S”, “D”, “T”, and “Q” are used to represent Single, Double, Triple and Quad Biax® sizes. The code also includes a reference such as T4 to represent the size of the tube. Rectangular headlamps are designated as “Rect” and the number of millimeters horizontally.
Brightness can refer to any of several technical terms used in lighting and is, therefore, ambiguous (See LUMINANCE).
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.
An obsolete term for luminous intensity
Candlepower (Mean Spherical)
Initial mean spherical candlepower at the design voltage. Mean spherical candlepower is the generally accepted method of rating the total light output of miniature lamps. To convert this rating to lumens, multiply it by 12.57 (4 pi).
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 (See INTEGRAL, SELF-BALLASTED LAMPS).
Resistance of the cathode in a Fluorescent lamp. It is measured “cold” before the lamp is turned on (Rc) or “hot” after the lamp is turned on (Rh). The ratio of the hot resistance to the cold resistance is also measured (Rh/Rc).
A type of metal halide lamp that uses a ceramic material for the arc tube instead of glass quartz, resulting in better color rendering (>
A GE brand name for metal halide lamps designed to operate on HPS ballasts, allowing a user to switch from the yellowish color of HPS to the white color of metal halide without changing ballasts. These products are available in both quartz metal halide and ceramic metal halide (CMH) versions.
Measure to identify the color of a light source, typically expressed as (x,y) coordinates on a chromaticity chart (See COLOR TEMPERATURE).
A system for measuring the color of the light emitted from a light source–either a primary source like a lamp or a secondary source like an illuminated object. Usually two numbers, x and y coordinates ranging from 0 to 1 specify the chromaticity.
Coefficient of Utilization (CU)
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.
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 (visible to the eye) unless the difference is more than 3-5 points.
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.
Color Temperature (Correlated Color Temperature – CCT)
” white and bluish-white (“cool”) sources, such as cool white (4100K) and natural daylight (6000K), have higher color temperatures. The higher the color temperature the whiter, or bluer, the light will be (See CHROMATICITY).
“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
(See DICHROIC REFLECTOR)
A term loosely used to denote a color temperature of around 4100 K. The Cool White (CW) designation is used specifically for T12 and other fluorescent lamps using halophosphors and having a CRI of 62.
An illuminance meter that measures the light level correctly irrespective of the angle the light is coming from. (See ILLUMINANCE METER)
Cost of Light
Usually refers to the cost of operating and maintaining a lighting system on an ongoing basis. The 88-8-4 rule states that (typically) 88% is the cost of electricity, 8% is labor and only 4% is the cost of lamps.
A special plastic shielding on the outside of tubular fluorescent lamps that effectively contains shattered glass particles if the lamp is broken. Such protection is mandated in many industries and locations, e.g. food packaging.
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.
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.
In High Intensity Discharge lamps the Bulb to Arc Angle is the angle off of center between electrodes and bulb. The Bulb to Base Angle is the angle off of center that the bulb is from the base.
GE Edison Award
An annual competition where lighting designers submit their best projects. The entries are judged by an international panel and awards are presented at a banquet accompanying Light Fair, the North American trade show for the lighting industry.
A measurement of how effective the light source is in converting electrical energy to LUMENS of visible light. Expressed in LUMENS-PER-WATT (LPW) this measure gives more weight to the yellow region of the spectrum and less weight to the blue and red region where the eye is not as sensitive.
The efficiency of a light source is simply the fraction of electrical energy converted to light, i.e. watts of visible light produced for each watt of electrical power with no concern about the wavelength where the energy is being radiated. For example, a 100 watt incandescent lamp converts 7% of the electrical energy into light
The efficiency of a luminaire or fixture is the percentage of the lamp lumens that actually comes out of the fixture (See LUMINOUS EFFICACY).
A condition under which a gas becomes electrically conducting and becomes capable of transmitting current, usually accompanied by the emission of visible and other radiation. An electric spark in air is an example of an electrical discharge, as is a welder’s arc and a lightning bolt. (See ARC, 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).
A ballast used with discharge lamps that consists primarily of transformer-like copper windings on a steel or iron core (See ELECTRONIC BALLASTS).
Electromagnetic Inference (EMI)
High frequency electronic ballasts and other electronic devices can produce a small amount of radio waves which can interfere with radio and TV. Federal mandated requirements must be met for EMI levels before an electronic device is considered FCC compliant. (FCC is the Federal Communications Commission.)
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.
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 (high intensity discharge) lamps (See ELECTROMAGNETIC BALLAST).
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 the light absorption in some types of luminaires. It is particularly effective at increasing the efficacy of baffled downlights.
(See OPEN FIXTURE RATED)
Energy Policy Act (EPACT)
Comprehensive energy legislation passed by the U. S. 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. Federal Canadian legislation sets similar minimum energy efficacy requirements for incandescent reflector lamps and common linear fluorescent lamps.
Energy Policy Act (EPACT) Indicator
Means this lamp is Federally regulated for Energy Efficiency (See ENERGY POLICY ACT).
GE’s product family of incandescent lamps with the element Neodymium added to the glass bulb. Neodymium filters out much of the yellow light produced by ordinary lamps. Less yellow means whites look whiter and colors appear more vibrant in spaces lighted with Enrich lamps.
A curve depicting the sensitivity of the human eye as a function of wavelength (or color). The peak of human eye sensitivity is in the yellow-green region of the spectrum. The normal curve refers to photopic vision or the response of the cones. (See Photopic, Scotopic, Fovea, Foveal vision)
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 (See BEAM ANGLE).
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.
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.” See additional details in the e-Catalogue Help Menu under the HID category.
A physical phenomenon whereby an atom of a material absorbs a photon of light an immediately emits a photon of longer wavelength. If there is a significant delay the phenomenon is called phosphorescence rather than fluorescence. It is interesting that “phosphors” used in lamps exhibit “fluorescence,” not “phosphorescence.” (See PHOSPHOR)
A high efficiency lamp utilizing an electric discharge through low pressure mercury vapor to produce ultraviolet (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.
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.
(See ILLUMINANCE METER).
Fovea, Foveal Vision
A small region of the retina corresponding to what an observer is looking straight at. This region is populated almost entirely with cones, while the peripheral region has increasing numbers of rods. Cones have a sensitivity peaking in the yellow and corresponding to the eye response curve (See PHOTOPIC, SCOTOPIC, EYE SENSITIVITY).
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.
(See AMBIENT LIGHTING)
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).
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).
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.
Halogen-IR (HIR) Lamp
GE designation for high-efficiency tungsten halogen lamps. HIR lamps utilize shaped filament tubes coated with numerous layers of materials that transmit light but reflect the heat (infrared) back into the filament. This reduces the power needed to keep the filament hot.
High Intensity Discharge (HID) Lamp
A general term for mercury, metal halide (GE ConstantColor® CMH®, Multi-Vapor®, MXR or Arcstream®) and high-pressure sodium (GE Lucalox®) 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 product light by an electrical discharge though sodium vapor operating at relatively high pressures and temperatures. GE markets these lamps under the trade name of Lucalox®.
An electronic device providing a high voltage pulse to initiate an electrical discharge. Typically, the ignitor is paired with or is a part of the ballast (See STARTER).
“The “density” of light (lumens/area) incident on a surface
A device that measures the illuminance at a location calibrated either in footcandles or in lux. (Also know as a light meter — See COSINE CORRECTED)
The method of lighting a space by directing the light from luminaires upwards towards the ceiling. The light scattered off the ceiling produces a soft, diffuse illumination for the entire area.
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. Genura®is an example of an induction lamp.
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.
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 (See RAPID START).
A popular term for a compact fluorescent lamp which includes a built-in ballast (See CFL).
Inverse Square Law
Formula stating that if you double the distance from the light source, the light level goes down by a factor of 4, if you triple the distance, it goes down by a factor of 9, and so on.
The 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 € 0.10/kWh, then the electricity cost for the 10 hours of operation would be 10 cents (1 x € 0.10)
The term used to refer to the complete light source package, including the inner parts as well a 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.
The lamp’s identification code. For Projection lamps, this is a 3-letter-number code uniquely identifying the lamp for ordering purposes. In some instances, lamps with 3-letter (ANSI) codes are offered in more than one design voltage, in which case the voltage required should also be specified when ordering. Some GE Projection Lamps have an ordering code comprising of two or more 3-letter ANSI codes – such as EM/EKS and DYS/DYV/BHC. The first code is the ANSI code, the secondary codes identify which lamp the multiple-coded lamp can directly replace. Only the first code appears on the lamp itself. Multiple-coded lamps are so-designated by General Electric for the convenience of the customer. In nearly all cases, Miniature and Sealed Beam lamps are marked with a General Electric Trade number recorded with ANSI.
Filament lamps: Incandescent, Halogen, Halogen-IR.
Discharge Lamps: Fluorescent, HID (High Intensity Discharge)
HID Lamps: Mercury, HPS (High Pressure Sodium), MH (Metal Halide) and CMH (Ceramic Metal Halide)
(See RATED LAMP LIFE).
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. Refer to the following chart for reference plane locations.
” MARGIN-BOTTOM: 8px”>”
|Base type||L.C.L Reference Plane Location|
|All screw bases (except Mini-Can)||Bottom of base contact|
|Mini-Can||Where diameter of ceramic base insulator is .531 inches|
|3-Contact Medium||Bottom of base contact|
|Mogul Medium Prefocus||Top of base fins|
|Mogul Prefocus||Top of base fins|
|Medium BiPost||Base end of bulb (Glass lamps)
Bottom of ceramic base (Quartz lamps)
|Mogul BiPost||Shoulder of posts (Glass lamps)
Bottom of ceramic base (Quartz lamps)
|2-Pin Prefocus||Bottom of ceramic base|
|S.C. or D.C. Bayonet Candelabra||Top of base pins|
|Medium Bayonet||Top of base pins|
|S.C. or D.C. Prefocus||Plane of locating bases on prefocus collar|
|Medium 2-Pin||Bottom of metal base shell|
Lighting Industry Federation (LIF) Code
For Showbiz/Specialty lamps, these are assigned by the Lighting Federation of London U.K. They ensure electrical and mechanical interchangeability of similarly coded lamps. LIF codes are divided into groups according to the primary application of the lamps.
(See ILLUMINANCE METER)
Light that is directed to areas where it is not needed, and thereby interferes with some visual act. Light pollution directed or reflected into the sky creates a “dome” of wasted light and makes it difficult to see stars above cities.
Light Trespass (Spill Light)
Light that is not aimed properly or shielded effectively can spill out at into areas that don’t want it: it can be directed towards drivers, pedestrians or neighbors. It is distracting and annoying and can sometimes be disabling.
A measure of the 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 about 840 lumens.
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.
A measure of “surface brightness” when an observer is looking in the direction of the surface. It is measured in candelas per square meter (or per square foot) and was formerly referred to as “photometric brightness.”
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 FOOTCANDLE)
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).
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, indium and dysprosium. Some lamp types may also utilize phosphor coatings. GE trade names include: Multi-Vapor®, ConstantColor® CMH®, PulseArc®, Staybright®, Watt-Miser®, ChromaFit and Arcstream®.
Typically referring to nighttime outdoor lighting conditions, the region between PHOTOPIC and SCOTOPIC vision (See SCOTOPIC).
A GE brand for metal halide lamps.
Open Circuit Voltage (OCV)
Open Circuit Voltage measured across the socket the lamp screws into, with the ballast powered on. It is dangerous to stick a voltmeter into such a socket without precise knowledge of the ballast because exceedingly high voltages could be present.
Operating Position or Burn Position
Mercury and High Pressure Sodium lamps may be operated in any burn position and will still maintain their rated performance specifications. Metal Halide and Low Pressure Sodium lamps, however, are optimized for performance in specific burn positions, or may be restricted to certain burn positions for safety reasons.
U = Universal burning position
HBU = Horizontal -15º to Base Up
HBD = Horizontal +15º to Base Down
HOR = Horizontal ±15º
H45 = Horizontal to -45º only
VBU = Vertical Base Up ±15º
VBD = Vertical Base Down ±15º
If no special burn position is noted, the burn position is universal.
For electrical discharge lamps, this is the voltage measured across the discharge when the lamp is operating. It is governed by the contents of the chamber and is somewhat independent of the ballast and other external factors.
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, is a precision pressed-glass reflector lamp. PAR lamps rely on both the internal reflector and prisms in the lens for control of the light beam.
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 (See FLOURESCENCE).
“Vision for which the cones in the eye are responsible
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 HIDlamp 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.
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.
A name for fused silica or melted sand from which many high-temperature containers are fashioned in the lighting industry. Quartz looks like glass but can withstand the high temperatures needed to contain high intensity arc discharges.
(See HALOGEN LAMPS).
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 designs. Full-range fluorescent lamp dimming is only possible with rapid start systems (See INSTANT START).
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 (See LIFE).
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
Room Cavity Ratio (RCR)
A shape factor (for a room, etc.) used in lighting calculations.
RCR = 5H (L+W) / L x W, or, alternately,
RCR = (2.5) Total Wall Area / Floor Area.
Where H = height, L = length and W = width of the room.
the flatter the room the lower the RCR.
A cubical room will have an RCR of 10
Vision where the rods of the retina are exclusively responsible for seeing, typically like the light levels in the countryside on a moonless, starlit night (See also PHOTOPIC, FOVEA, FOVEAL VISION MESOPIC).
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 ration 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.
A discharge lamp with an integral ballasting device allowing the lamp to be directly connected to a socket providing line voltage (See CFL).
For Projection lamps, this is defined as the dimensions of the rectangular area, centered on the lamp axis, within which all luminous parts of the filament lie, when viewed perpendicular to the axis of the filament coil or to the plane of C-13 and C-13D filaments.
Spacing to Mounting Height Ratio
sometimes called spacing criterion. It is OK to have fixture spaced closer than the spacing criterion suggested by the manufacturer but not farther, or you will get dark spots in-between fixtures.
Ratio of fixture spacing (distance apart) to mounting height above the work plane
Specification Series (SP) Colors
Energy-efficient, all-purpose, tri- phosphor fluorescent lamp colors that provide good color rendering. The CRI for SP colors is 70 or above and varies by specific lamp type.
Specification Series Deluxe (SPX) Colors
Energy-efficient, all-purpose, tri- phosphor fluorescent lamp colors that provide better color rendering than Specification Series (SP) colors. The CRI for SPX colors is 80 or above and varies by specific lamp type. All GE CFL products use SPX phosphors.
Spectral Power Distribution (SPD)
A graph of the radiant power emitted by a light source as a function of wavelength. SPDs provide a visual profile or “finger print” of the color characteristics of the source throughout the visible part of the spectrum.
See SPECTRAL POWER DISTRIBUTION (SPD).
A colloquial term referring to a reflector lamp with a tight beam of light, typically around 10 degrees or less. It comes from the fact that such a lamp produces a narrow spot of light as opposed to a wide flood of light.
GE’s special barrier coating applied on the inside of all GE T8 fluorescent lamps, a well as some other lamp types, to enhance lamp life and deliver superior lumen maintenance.
An electronic module or device used to assist in starting a discharge lamp, typically by providing a high-voltage surge (See IGNITOR).
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 groundwater (See ECOLUX).
(See TOTAL HARMONIC DISTORTION)
Total Harmonic Distortion (THD)
A measure of the distortion caused by ballasts and other inductive loads 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 components.
(See HALOGEN LAMP).
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 is 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.
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 – 180-220 nm
- Bactericidal (germicidal) – 220-300
- Erythemal (skin reddening) – 280-320
- “Black” light – 320-400
UV-B (280-315 nm) and UV-C (100-280 mm).
The International Commission on Illumination (CIE) defines the UV band as UV-A (315-400 nm)
” sometimes called “reflected glare.” You might have dealt with veiling reflections when you have to tilt a shiny magazine to avoid glare so as to read it, or struggled with reading a computer monitor because of the reflection of a window or a light fixture (See GLARE).
“Effective reduction in contrast between task and its background caused by the reflection of light rays
Visual Comfort Probability (VCP)
For a given lighting scheme, VCP is a ratio expressed as a percent of people who, when viewing from a specific location and in a specified direction, find the system acceptable in terms of glare (See GLARE).
The task associated with seeing
A measure of “electrical pressure” between two points. The higher the voltage, the more current will be pushed through a resistor connected across the points. The volt specification of an incandescent lamp is the electrical “pressure” required to drive it at its designed point. The “voltage” of a ballast (e.g. 277 V) refers to the line voltage it must be connected to.
For Automotive lamps, voltage at which the lamp is designed to provide the amperes, candlepower, and laboratory life characteristics. For Projection lamps, the voltage shown is the design voltage of the lamp, on which the life and wattage ratings are based. Lamps for which 115-120 is shown in the Volts column are designed at 118 volts. Lamps are available only in the design voltage(s) shown. When ordering lamps listed for more than one voltage, be sure to specify the voltage required. (Supply voltage variation can significantly affect lamp life.)
A unit of electrical power. Lamps are rated in watts to indicate the rate at which they consume energy (See KILOWATT HOUR).
Wattage Indicator Reduced
Indicates that this is a reduced wattage option for lamps normally used in this application. Be sure to check wattage, lumens and life to determine which lamp is best suited to your needs.
Plane at which work is done and at which illumination is specified and measured
Working Distance (Typical)
For Multi-Mirror® and other reflector Quartzline® lamps and MARC™ Projection lamps, the Working Distance shown is the distance from the front surface of the reflector rim to the film plane, in the optical system for which the lamp was first designed. In most cases, it provides a uniform plane of light for the intended aperture.