Light_Vocabulary



**AC (Alternating Current)** Current which flows in one direction and then the other, alternately.

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.
 * ANSI (American National Standards Institute) **

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

**ANSI Codes** 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.

 **Bayonet** 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.

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

**Chromaticity** Measure to identify the color of a light source, typically expressed as (x,y) coordinates on a chromaticity chart.

**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.

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

<span style="color: #09c8c8; font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">**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.

<span style="font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">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.
 * <span style="color: #09c8c8; font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">Electromagnetic Spectrum **

<span style="font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">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")
 * <span style="color: #09c8c8; font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">Flood **

<span style="font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">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.
 * <span style="color: #09c8c8; font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">Fovea, Foveal Vision **

<span style="font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">A plot with lines connecting points of equal luminous intensity around a source.
 * Isocandela Plot **

<span style="font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">A line plotted to show points of equal illuminance (lux or footcandles) on a surface illuminated by a source or sources.
 * Isolux Plot (or Isofootcandle Plot) **

<span style="font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">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).
 * <span style="color: #09c8c8; font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">Mean Lumens **

<span style="font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">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.
 * Rated Lamp Life **

<span style="font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">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.
 * <span style="color: #09c8c8; font-family: Tahoma,Geneva,sans-serif; font-size: 110%;">Spot **