[Ord. 1631, 8/14/2000, Section XII]
CANDELAThe SI unit of luminous intensity. One candela is one lumen per steradian (lm/sr).
CUTOFF ANGLEThe vertical angle measured above nadir at which the light source from a luminaire is no longer visible.
CUTOFF LUMINAIREA luminaire light distribution is designed as cutoff when the candlepower per 1,000 lamp lumens does not numerically exceed 25 (2.5%) at an angle of 90° above nadir (horizontal) and 100 (10%) at a vertical angle of 80° above nadir.
FIXTUREThe assembly that holds the lamp along with any globe, shade, or other covering surrounding the lamp.
FOOTCANDLE (FC)A unit of illuminance. One footcandle is one lumen per square foot (lm/ft2).
GLAREA subjective term used to describe any illumination from a light source that strikes the viewer's eye causing annoyance, discomfort, or loss in visual performance or visibility.
HEIGHT OF LUMINAIREIt is measured as the vertical distance between the top of the luminaire and the ground directly below the luminaire.
ILLUMINANCEThe areal density of the luminous flux incident at a point on a surface. It is measured in footcandles.
ILLUMINATIONA non-technical term designating the state of emitting visible light or having visible light reflected off an object.
LAMPThe component of a luminaire that produces the actual light.
LIGHTRadiant energy that is capable of exciting the retina and producing a visual sensation.
LIGHT LOSS FACTOR (LLF)The ratio of illuminance for a given area to the value that would occur if lamps operated at their initial rated lumen output and if no system variation or depreciation had occurred.
LIGHT TRESPASSA subjective perception of undesirable illumination including the following examples:
• | The classic light shining in a window |
• | Unwanted light on an adjacent property |
• | Excessive brightness (glare) in the normal field of vision |
LIGHTING SYSTEMA functionally related group of interacting luminaires used to illuminate a specific area.
LUMENSI unit of luminous flux. Photometrically, it is the luminous flux emitted within a unit solid angle (one steradian) by a point source having a uniform luminous intensity of one candela.
LUMINAIREA complete lighting unit consisting of a light source(s) together with all parts designed to control the light distribution, and any other mechanical, electrical, or decorative parts.
LUMINANCEThe emitted or reflected light from a surface the amount of which causes perceived brightness. The unit of luminance is the candela per square meter (cd/m2).
LUMINOUS FLUXRadiant flux (radiant power); the time rate of flow of radiant energy evaluated in terms of a standardized visual response.
LUMINOUS INTENSITYThe luminous flux per unit sold angle in the direction in question. Can be expressed in candelas or lumens per steradian (lm/sr).
PARKA tract of land reserved for public use as playgrounds, trails, paths, natural areas, or recreational areas and other public areas.
SECURITY LIGHTINGLighting designed for and expressly used to deter criminal activity by illuminating a specific area at nighttime.