22 August 2006
UFGS Unified Facilities Guide Specifications
UL Underwriters Laboratories
W - Watts
Adaptation the process by which the retina becomes accustomed to more or less
light than it was exposed to during an immediately preceding period. It results in a
change in the sensitivity to light.
Altitude the angular distance of a heavenly body measured on the great circle that
passes perpendicular to the plane of the horizon, through the body and through the
zenith. It is measure positively from the horizon to the zenith, from 0 degrees to 90
Ambient Lighting lighting throughout
an area that produces general illumination
Area Lighting Luminaire a complete lighting device consisting of a light source and
ballast, where appropriate, together with its direct appurtenances such as globe,
reflector, refractor, housing, and such support as is integral with the housing. The pole,
post, or bracket is not considered part of the luminaire.
Average Luminance luminance is a property of a geometric ray. Luminance as
measured by conventional meters is averaged with respect to two independent
variables, area and solid angle; both must be defined for a complete description of a
Azimuth the angular distance between the vertical plane containing a given line or
celestial body and the plane of the meridian.
Baffle a single opaque or translucent element to shield a source from direct view at
certain angles, to absorb or block unwanted light, or to reflect and redirect light.
a device used with
an electric-discharge lamp
to obtain the necessary circuit
conditions (voltage, current, and waveform) for starting and operating.
Ballast Factor the fractional flux
of a fluorescent lamp operated
on a ballast
compared to the flux when operated on the standard (reference) ballast specified for
rating lamp lumens.
Bollard luminaires having the appearance of a short, thick post, used for walkway and
grounds lighting. The optical components are usually top-mounted.
Bowl an open-top diffusing glass or plastic enclosure used to shield a light source
from direct view and to redirect or scatter the light.
Bracket (mast arm) an attachment to a lamp post or pole from which a luminaire is
Candela, cd the SI unit of luminous intensity, equal to one lumen per steradian