As used in this chapter, the following terms shall have the meanings
indicated:
AREA LIGHT
A fixture designed for illumination of a broad area. Area
lights include, but are not limited to, streetlights, parking lot
lights and yard lights over 1,800 lumens.
AVERAGE HORIZONTAL FOOTCANDLE
The average level of illuminance for a given situation measured
at ground level with the light meter placed parallel to the ground.
It can be also determined by the "Key" on a lighting plan as provided
by a lighting manufacturer's application department.
CORRELATED COLOR TEMPERATURE (CCT)
The perceived color of the light emitted by a lamp, expressed
in Kelvin (K) units. Generally, the lower the Kelvin rating the "warmer"
the light; the higher the rating, the "cooler" or more blue the light.
Incandescent bulbs emit approximately 2,300 Kelvin.
ESSENTIAL LIGHTING
Light that is used for a specified period of time, which
is necessary for location identification or public circulation purposes.
EXCESSIVE LIGHTING
Illuminance levels beyond that which is required for safety,
as recommended in IESNA Recommended Practices, or higher than five
FC on any lit surface unless a higher level is indicated on the Table
of Limits of Illumination Levels.
EXTERIOR LIGHTING
Temporary or permanent lighting equipment that is installed,
located or used in such a manner with the intention to cause light
rays to shine outdoors.
FIXTURE (ALSO CALLED "LUMINAIRE")
The bulb and the assembly that holds the bulb (or lamp) in
a lighting system, including reflecting elements, shielding elements,
cover glass or lenses, the ballast, and the housing. For purposes
of determining total light output from a luminaire or light fixture,
lighting assemblies which include multiple unshielded or partially
shielded lamps on a single pole or standard shall be considered as
a single unit.
FLOODLIGHT
A lamp or fixture intended to light a large area, and which
can produce light above the fixture. Such lamps (bulbs) may incorporate
prismatic lenses that distribute the light in various directions.
FOOTCANDLE ("FC")
The basic unit of illuminance (the amount of light falling
on a surface). Footcandle measurement is taken with a light meter.
One footcandle is approximately equal to the illuminance produced
by a light source of one candela in intensity, measured on a surface
at a one-foot distance from the source. Horizontal footcandles measure
the illumination striking a horizontal plane. Footcandle values can
be measured directly with certain handheld incident light meters.
FULLY SHIELDED OR ZERO UPLIGHT
A fixture designed, constructed and installed in such a manner
that all light emitted by it, either directly from the lamp or a diffusing
element, or indirectly by reflection or refraction from any part of
the fixture, is projected in a fixed direction below the horizontal.
It can be identified without a manufacturer's photometric report.
Also referred to as "zero uplight."
GLARE
The sensation produced by a light source within the visual
field that is sufficiently brighter than the level to which the eyes
are adapted, which can cause annoyance, discomfort, or loss in visual
performance and visibility. The magnitude of glare depends on such
factors as the size, position, brightness of the source, and on the
brightness level to which the eyes are adapted.
HID LIGHTING
A family of bulb types that are known as "high-intensity
discharge," including high-pressure sodium, mercury vapor, and metal
halide. These types may require a warmup time, usually require a ballast,
and have a higher lumen output per watt than incandescent (or halogen)
lamps.
IESNA
Illuminating Engineering Society of North America (IES or
IESNA), a private-membership organization that establishes updated
standards and illumination guidelines for the lighting industry.
IESNA RECOMMENDED PRACTICES
The most current publications of the IESNA setting forth
illuminance levels for different task areas, e.g., walkways, streets,
sportslights, etc.
ILLUMINANCE
The density of light falling on any point of a surface, usually
measured in footcandles in the United States. See "footcandle."
KELVIN
The unit of measurement used to characterize the color of
light emitted by a lamp. See also "correlated color temperature."
LAMP
The generic term for an artificial light source, to be distinguished
from the whole assembly (see "fixture"); commonly referred to as the
"light bulb."
LED
Light emitting diodes are assembled into a lamp to emit light.
LEDs are energy efficient, directional, and have a long-life for maintenance
purposes. Unfiltered LEDs are high in the blue spectrum (6,000+ Kelvin)
and require colored filters to produce "white" light. Also referred
to as "solid state lighting."
LIGHT
The form of radiant energy acting on the retina of the eye
to make sight possible.
LIGHTING ASSEMBLY
Any or all parts of a fixture that function to produce light,
including the bulb, assembly, ballast, mounting features and/or pole.
LIGHT LEVEL
The illuminance on a surface, as measured by a light meter
or reported in photometric calculations. Light levels are indicated
in footcandle measurements on a lighting plan and may also be expressed
as uniformity ratios and as isofootcandle plots.
LIGHT POLLUTION
Any adverse effect of man-made light, including but not limited
to glare, light trespass, skyglow, visual clutter, wasted energy due
to excessive or unnecessary lighting, or any man-made light that unnecessarily
diminishes the ability to view the night sky or is disruptive to flora
and fauna.
LIGHT SOURCE
The light bulb and all reflecting and refracting parts of
the fixture that transmit light.
LIGHT TRESPASS
Light projected onto the property of another or into the
public right-of-way when it is not required or permitted to do so.
For reference, full moonlight averages 0.01 footcandle.
LUMEN
A unit used to measure the actual amount of light that is
produced by a bulb. The lumen quantifies the amount of light energy
produced by a lamp at the lamp, not by the energy input, which is
indicated by the wattage. For example, a 75-watt incandescent lamp
can produce 1,000 lumens while a 70-watt high-pressure sodium lamp
produces 6,000 lumens. Lumen output is listed by the manufacturer
on the packaging or can be available from the manufacturer's
website.
LUMINANCE
The brightness of a source of light.
MAINTAINED ILLUMINANCE
The light levels that are produced by a lamp and in a fixture
after a period of time, taking the normal losses due to lamp aging
and fixture dirt accumulation into account.
MOUNTING HEIGHT
The distance from level ground to the lowest light-emitting
part of the fixture.
PARTIALLY SHIELDED
A fixture, which incorporates a partial shield around the
lamp, concealing the lamp from view only in certain directions.
PHOTOMETRICS
Technical test reports that indicate light distribution and
performance from a fixture. Photometric reports may include candlepower
distribution data, cutoff classifications, isofootcandle charts, etc.
These are generally available from the fixture manufacturers as IES
files or isofootcandle plots.
SHIELD or SHIELDED
An opaque device that is attached to a light fixture to prevent
light from being emitted in certain directions. Auxiliary "back" or
"house-side" shielding added to an already fully shielded fixture
can help limit trespass where a fixture is located near a property
line.
SKYGLOW
The overhead glow from light emitted sideways and upwards,
including light reflected upward from the ground or other surfaces.
Skyglow is caused by the reflection and scattering of various forms
of light by dust, water, and other particles suspended in the atmosphere.
Among other effects, skyglow reduces one's ability to view the
night sky. Different sources of light, in equal quantities, can contribute
differently to sky glow.
TEMPORARY LIGHTING
Lighting that is intended to be used for a limited time and
removed thereafter.
UL RATING
Refers to "Underwriters Laboratory," a commercial agency
that certifies the maximum safe wattage for fixtures and other electrical
devices. A UL label indicating the maximum safe wattage is affixed
or imprinted on all electrical fixtures which are offered for sale.
UNIFORMITY RATIO (U RATIO)
A ratio that describes uniformity of illuminance across an
area. The uniformity ratio may be a ratio of the maximum-to-minimum
illuminance or the average-to-minimum illuminance. For example, if
the Illuminating Engineering Society recommends an average-to-minimum
ratio of 4:1 for a parking lot, the minimum illuminance should be
no less than 1/4 of the average illuminance across the parking lot.
Uniformity ratios meeting professional recommendations will reduce
adaptation problems and promote better nighttime vision.