Outdoor Lighting Glossary

Come across a lighting word you aren't sure of? Completely new to the world of lighting? We feel your pain! Here you will find a collection of terms and concepts that should help to make your life easier.

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Select the first letter of the word from the list above to jump to appropriate section of the glossary.

Efficacy - May refer to either the efficiency of the lamp (lumens per watt) or that of the luminaire (lumens emitted by the fixture compared to those emitted by the unshielded lamp).

Efficiency - see Efficacy

Electric Discharge Lamp - A light source that produces light by passing a current between electrodes through a vapor or gas; includes fluorescent, high intensity discharge, and other lamps.

Electroluminescence - The emmision of light from a phosphor excited by an electromagnetic field. An example: a light source technology used in exit signs that provides uniform brightness, long lamp life (approximately eight years), while consuming very little energy (less than one watt per lamp). The emmision of light from a phosphor excited by an electromagnetic field.

Electronic Ballast - A ballast that uses semiconductor components to increase the frequency of fluorescent lamp operation-typically in the 20-40 kHz range. Smaller inductive components are used to provide the lamp current control. Fluorescent system efficiency is increased due to high frequency lamp operation.

Electronic Dimming Ballast - A variable output electronic fluorescent ballast.

Emission Coating - An oxide coating deposited on a cathode that emits electrons when heated.

Emissivity/Emittance - The ratio of radiance (for directional emissivity) or radiant exitance (for hemispherical emissivity) of an element of surface on a temperature radiator to that of a blackbody at the same temperature. By Kirchoff's Law, for a given wavelength of the electromagnetic spectrum, emissivity of a surface equals its absorptivity (and is the reciprocal of its reflectivity).

End Blackening - Darkening around the ends of a fluorescent tube caused by the emitter paste on the electrodes evaporating and collecting on the glass.

Energy Survey - Synonymous with "cost calculations," "energy audit," etc.; a systematic cost comparison of an existing system to a proposed system; accounts for electrical, material and maintenance/manpower costs.

Energy-Saving Ballast - A type of magnetic ballast designed so that the components operate more efficiently, cooler and longer than a "standard magnetic" ballast. By U.S. law, standard magnetic ballast's can no longer be manufactured.

Energy-Saving Lamp - A lower wattage lamp, generally producing fewer lumens.

EPA - Effective Projected Area; A value given to outdoor pole mounted lighting equipment based on fixture surface area and shape. Used in outdoor applications to calculate wind loading data to determine proper pole size necessary to support fixture.

Equivalent Sphere Illumination (ESI) - The level of sphere illumination which would produce task visibility equivalent to that produced by a specific lighting environment. Suppose a task at a given location and direction of view within a specific lightings system has l00 fc of illumination. Suppose this same task is now viewed under sphere lighting and the sphere lighting level is adjusted so that the task visibility is the same under the sphere lighting as it was under the lighting system. Suppose the lighting level at the task from the sphere lighting is 50 fc for equal visibility. Then the Equivalent Sphere Illumination of the task under the lighting system would be 50 ESI fc.

ER (Elliptical Reflector) - Lamp whose reflector focuses the light about 2" ahead of the bulb, reducing light loss when used in deep baffle downlights.

Etch - Logo, brand name, and product information that appears on glass envelope of lamp.

Exitance - The density of light reflecting from a surface at a point, measured in lumens per square foot (formerly "footlamberts"). It is determined by multiplying the footcandles striking a diffuse reflecting surface times the reflectance of that surface.

Extended Life Lamps - Incandescent lamps that have an average rated life of 2500 or more hours and reduced light output compared to standard general service lamps of the same wattage.

Eyeball - Fixture, usually recessed, loosely resembling an "eyeball"; can be rotated to point in desired direction.