Directional lighting to emphasize a particular object or draw attention to a display item.


The process by which the human eye adjusts to a change in light level.


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


The surrounding temperature within an environment.


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.


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


The "positive" terminal of a diode.


Ballast type used to operate lamp in accordance with ANSI standard.


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 for a lamp (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 parameters 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).


In High Intensity Discharge lamps: the distance between the electrode tips, which represents the physical length of the electrical discharge.


This field designates the type of gas or vacuum filling a volume or chamber of the lamp. This chamber might contain a filament or it might refer to the bulb which contains the arc tube.


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.


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.


The socket is the receptacle connected to the electrical supply; 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.


The maximum operating temperature permitted for the base in Celsius. Fixture manufacturers need to ensure that these conditions are satisfied in their fixture.


A style of bulb base which uses keyways instead of threads to connect the bulb to the fixture base. The bulb is locked in place by pushing it down and turning it clockwise.


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 ).


The total lumens present within the portion of the beam contained in the beam angle.


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.


A popular term referring to a light source emitting mostly near UV (320 to 400 nm) and very little visible light.


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.


Whether or not the top of the miniature lamp has a blacktop coating. The coating is used to control unwanted brightness or glare.


A short, thick post with a light at its top, used for grounds and outdoor walkway lighting.


Brightness can refer to any of several technical terms used in lighting and is, therefore, ambiguous (See LUMINANCE).


A loose way of referring to a lamp. "Bulb" refers to the outer glass bulb containing the light source.


The type of glass (or quartz) used in the glass envelope surrounding the light source. The material can also have coatings applied to achieve particular performances.


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.


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; current practice is to refer to this simply as candelas.


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).


A graphical presentation of the distribution of light intensity of a light source, usually a reflector lamp or luminaire.


The "negative" terminal of a diode.


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).


Refers to the luminous intensity at the center of the beam of a blown or pressed reflector lamp (such a s a PAR lamp). Measured in candelas.


A very small square of semi-conducting material. Also known as a "die," it is the "active" light-emitting component of an LED.


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.


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.


LEDs are designed to give off a specific color emission. The dominant wavelength is a quantitative measure of an LED color as perceived by the human eye and is usually measured in nanometers (a billionth of a meter). In order to specify an LED, you must specify the color or dominant wavelength range required for your application. Some applications may have color constraints in order to meet specific government specifications or regulatory guidelines.


LEDs are sorted according to their wavelength or CIE coordinates into different groupings or "bins."


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.


Draws attention to the fact that this is a lamp with high color rendering, which helps objects and persons illuminated to appear more true to life.


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 (6000K), have higher color temperatures. The higher the color temperature the whiter, or bluer, the light will be (See CHROMATICITY).


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.


A term loosely used to denote a color temperature of around 4100K. 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).


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.


The ratio of the peak lamp current to average lamp operating current (RMS). The lower the current crest factor is, the gentler the ballast is on the lamp.


Whether the operational voltage is based on Alternating Current or Direct Current.


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


A lamp resembling the color of daylight, typically with a color temperature of 5500K to 6500K.


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.





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


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


A quantitative measure of the color of an LED as perceived by the human eye. It is usually measured in nanometers (a billionth of a meter).


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.


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 its electrical energy into light; discharge lamps convert 25% to 40% 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).


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).


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.


GE Lighting Solutions offers products with several types of encapsulant finishes. An encapsulant finish may have some effect on the photometric output of the device. The unique encapsulant finish of GE Lighting Solutions product is identified in the 11th position of the part number, i.e., GERD5R015-CC.

Available Encapsulant Finishes:
Water Clear: Colorless in appearance.
Diffused: A diffuser scatters the light emitted and widens the viewing angle, resulting in a more even distribution of light. Diffusing the encapsulant may also reduce the intensity of the device. Diffused LEDs are ideal for applications where the LED acts as an indicator, rather than an illuminator. Diffused LEDs are also usually tinted.
Tint: Tinting an LED can be accomplished by adding a dye to the encapsulant similar in color to the light emitted. This allows identification of the LED color in the OFF state, as well as offering color filtering of direct sunlight. Tinting may also reduce the intensity of the device.

GE Lighting Solutions can provide both the tinting and diffusing of the LED encapsulant.




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.


Means this lamp is Federally regulated for Energy Efficiency (See ENERGY POLICY ACT).


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 U.S. Federal agency that regulates emissions in the radio frequency portion of the electromagnetic spectrum. Part 18 of the FCC rules specifies electromagnetic interference (EMI) from lighting devices operating at frequencies greater than 9 kilohertz (kHz). Typical electronically-ballasted compact fluorescent lamps operate in the 24 - 100 kHz frequency range.


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-Catalog Help Menu under the HID category.


The periodic variation in light level caused by AC operation that can lead to strobe effects.


Used to refer to the beam pattern of a reflector lamp, which disperses the light over a wide beam angle, typically 20 degrees or more. ("Flood" as opposed to "spot")


A luminaire used to light a scene or object to a level much brighter than its surroundings. Usually floodlights can be aimed at the object or area of interest.


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.




An obsolete term referring to a luminance of 1/? candelas per square foot.


Current through a diode in the direction of its greatest conduction.


The voltage across a diode for a given forward current.


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).


The stated operating frequency in Hz of a discharge lamp.


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.



GE Lighting Solution's incandescent-look LED Traffic Signal.




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.


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.


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.


Lighting designed for (typically) industrial locations with a ceiling height of 25 feet and above.


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.


Time it takes for a High Intensity Discharge lamp to reach 90% of light output after going from on to off to on.


A GE designation for a family of metal halide lamps that operate on a mercury ballast. Designed as a simple retrofit for mercury lamp.


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; i.e., the light level on a surface. Illuminance is measured in footcandles or lux.


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.)


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.


The method of lighting a space by directing the light from luminaires upward 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 as a result, generally have longer life than standard lamps.


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 that includes a built-in ballast (See CFL).


LEDs are sorted according to their intensity values into different groupings or "bins."


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.


A plot with lines connecting points of equal luminous intensity around a source.


A line plotted to show points of equal illuminance (lux or footcandles) on a surface illuminated by a source or sources.


A unit of temperature starting from absolute zero, parallel to the Celsius (or Centigrade) scale. 0C is 273K.


The measure of electrical power equal to 1000 watts.


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).


The term used to refer to the complete light source package, including the inner parts as well a the outer bulb or tube. "Lamp" 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.


Referenced by IEC as Dimension C. Also referred to as "Base Face to Top of Lamp."


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).


Referenced by IEC as Dimension A.


A metallic frame used for mounting and connecting LED chips. The leadframe functions as the electrical leads of the device.


A transparent or semi-transparent element which controls the distribution of light by redirecting individual rays. Luminaires often have lenses in addition to reflectors.




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


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.

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


A solid that directly converts electrical impulses into light. Some LEDs incorporate fluorescent materials to change the color characteristics of the emitted light.


The product of all factors that contribute to lowering the illumination level including reflector degradation, dirt, lamp depreciation over time, voltage fluctuations, etc.




Light that is directed to areas where it is not needed. For example, light pollution directed or reflected into the sky creates a "dome" of wasted light and makes it difficult to see stars above cities.


Light that is not aimed properly or shielded effectively can spill out into areas where it is not required, distracting drivers, pedestrians and neighbors. It can be annoying and occasionally disabling.




For Stage & Studio 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.


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.


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) and 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.


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


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 measure of the visibility of a light source generally expressed in candelas. It is defined as luminous flux per unit solid angle (steradian) in a given direction.


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


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).


Usually refers to the screw base typically used in household incandescent lamps. A medium bipin base is commonly used in T12 and T8 fluorescent lamps.


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.


Typically referring to nighttime outdoor lighting conditions, the region between PHOTOPIC and SCOTOPIC vision (See SCOTOPIC).


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.


A screw base used on larger lamps, e.g., many HID lamps.


Light with only one wavelength (i.e., color) present.


Distance from the bottom of the fixture to either the floor or work plane, depending on usage.


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


The standardized part number used by the U.S. Government for procurement.


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.


Lamps that are approved for burning in open fixtures (as opposed to enclosed fixtures which have an acrylic lens or plate glass enclosure).


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: 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.


LEDs are available in either leaded-through-hole, or surface-mount packages. Through-hole LEDs are ideal for wave solder circuit board applications. Most through-hole LEDs are 2-leaded devices. Common through-hole package sizes include 3mm (T-1) and 5mm (T-1 *) diameter parts. Surface-mount packages are best used with reflow assembly. SMD devices are also useful when package size constraints are an issue.


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.


The maximum wavelength of an LED.


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 FLUORESCENCE).


The measurement of light and related quantities.


Vision for which the cones in the eye are responsible; typically at high brightness and in the foveal or central region (See SCOTOPIC , FOVEA, FOVEAL VISON ).


LEDs can be created with specific physical variations to make it unique. A GE Lighting Solutions' products unique physical attribute is identified in the 12th position of the part number, i.e., GERD5R015-CC. These may include:

Flange: A flange is a rim added to the base of some LED lamps. The flange increases the diameter at the base, adding stability to the device, especially when mounted flush to a surface. The flange may also aid in fitting the LED into various secondary optic assemblies.

Stand-offs: Stand-offs allow the LED to be positioned without coming in direct contact with the printed circuit board (PCB). Stand-offs are ideal for applications where multiple LEDs are required to be at identical heights above a common plane, such as a circuit board.


(See CFL).


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.


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.


An HID ballast with a high voltage ignitor to start the lamp.


Generally refers to a compact fluorescent lamp containing 4 U-shaped tubes.


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.




GE Lighting Solutions' standard LED Traffic Signal.


A general term for the release of energy in a "wave" or "ray" form. All light is radiant energy or radiation, as is heat, UV, microwaves, radio waves, etc.


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 hybrid designs. Full-range fluorescent lamp dimming is only possible with rapid start systems (See INSTANT START).


For most lamp types (LEDs not included), 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).


The ratio of light reflected from a surface to that incident upon it.


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.


Voltage across the diode for a given reverse current.


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.
A cubical room will have an RCR of 10; the flatter the room, the lower the RCR.


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).


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.


(See CFL).


The maximum operating temperature of the seal of the lamp in Celsius.


A discharge lamp with an integral ballasting device allowing the lamp to be directly connected to a socket providing line voltage (See CFL).


Perfected at GE and applied throughout the GE Lighting Solutions organization, Six Sigma is a quality initiative that allows us to produce and deliver high-quality LED solutions with predictable reliability.


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.


Ratio of fixture spacing (distance apart) to mounting height above the work plane; sometimes called spacing criterion. It is OK to have fixtures spaced closer than the spacing criterion suggested by the manufacturer, but not farther, or you will get dark spots in-between fixtures.


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.


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.


A graph of the radiant power emitted by a light source as a function of wavelength. SPDs provide a visual profile or "fingerprint" of the color characteristics of the source throughout the visible part of the spectrum.




Reflection from a smooth, shiny surface, as opposed to diffuse reflection.


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.


A Color Designation for GE Ceramic Metal Halide Lamps with superior Color Rendering ~ 90.


An electronic module or device used to assist in starting a discharge lamp, typically by providing a high-voltage surge (See IGNITOR).


The minimum ambient temperature at which a lamp will start reliably.


The full 14 digit case code used on GE's content label.


Skin reddening and inflammation caused by overexposure to sources containing UV-B and/or UV-C.


A term referring to the lamp and ballast combination, and sometimes to the entire lighting delivery system including the fixture, the optics, the particular layout and the lighting controls.



An LED lamp package. Type T-1= 0.125 inch lamp diameter or a 3.18mm (Referred to as a 3mm) lamp diameter.


An LED lamp package. Type T-1 3/4= 0.2188 inch lamp diameter or a 5.56mm lamp diameter.


Supplemental lighting provided to assist in performing a localized task, e.g., a table lamp for reading or an inspection lamp for fabric inspection.


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 ).


The minimum or maximum allowed voltage allowed into lamp from ballast under varying conditions as specified.


GE Lighting Solution's robust and patented Tetra LED Lighting Systems enable infinite signage and architectural application possibilities indoors or out. Judged against the performance of standard neon or fluorescent lamps, GE Tetra LED solutions provide significant energy cost reductions, easier jobsite installation, less frequent maintenance and more consistent brightness.


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.


A long, recessed lighting unit, usually installed in an opening in the ceiling.




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 nm
  • Erythemal (skin reddening) - 280-320 nm
  • "Black" light - 320-400 nm

  • The International Commission on Illumination (CIE) defines the UV band as UV-A (315-400 nm); UV-B (280-315 nm) and UV-C (100-280 nm).


A private organization that 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.


The 12 digit case code derived from the last 12 digits of the 14 digit SCC code on GE's case content label.


The 12 digit code on the saleable unit that is used for scanning at the register.


Lighting from light sources on a wall typically above eye level, shielded by horizontal panels. The light may be upward or downward directed.


Effective reduction in contrast between task and its background caused by the reflection of light rays; sometimes called "reflected glare." When you tilt a shiny magazine to avoid glare while reading it, or if you struggle with viewing a computer monitor because of the reflection of a window or a light fixture, you're dealing with veiling reflection (See GLARE).


The off-axis angle where the display may be satisfactorily viewed (defined by lenses, obstructions or intensity decrease).

The viewing angle referred to as the 2-half theta angle (2Q * ) indicates how focused the light is when emitted from the LED. This angle is determined by measuring the angle from direct on-axis to the angle where intensity falls to * of the on-axis intensity, and then multiplying this difference by 2.

The shape of the encapsulant dome lens controls the viewing angle of the LED. Flat LEDs without domes generally have a very wide viewing angle. The choice of viewing angle also affects the LED intensity. As the viewing angle is increased, more area is covered by light, however the on-axis intensity is reduced.

For applications where the LED will project light onto a small area, or on an object far from the emitter, a narrow viewing angle is ideal. For applications where the LED will project light onto a large area, or on an object very close to the emitter, a wide viewing angle is ideal. For instance, backlighting an indicator or switch in a cavity of less than 18mm would typically call for a surface mount LED with a 120Æ' viewing angle. Illuminating an object that is several square inches in size, but just two feet away, would require a 5mm LED with a 20Æ' or smaller viewing angle.

Oval-viewing angle LEDs are available for applications requiring illumination of areas that are not square or circular. These LEDs have a wider viewing angle in either the horizontal or vertical direction.


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; objects and details that must be seen to perform an activity.


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.


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.


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.)


The maximum operating bulb wall temperature in Celsius.


The time it takes for a High Intensity Discharge lamp to reach 90% of light output after being turned on.


Refers to a color temperature around 3000K, providing a yellowish-white light.


A unit of electrical power. Lamps are rated in watts to indicate the rate at which they consume energy (See KILOWATT HOUR).


Indicates a reduced wattage option for lamps normally used in a particular application. Be sure to check wattage, lumens and life to determine which lamp is best suited to your needs.


The distance between two neighboring crests of a traveling wave. The wavelength of light is between 400 and 700 nanometers.


Plane at which work is done and at which illumination is specified and measured; unless otherwise indicated, it is assumed to be a horizontal plane 30 inches above the floor (tabletop height) having the same area as the floor.


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.