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XII.5
Glossary
F
Federal Communications Commission (FCC)
The U. S. Federal agency that regulates
emissions in the radio frequency portion of the
electromagnetic spectrum. Part 18 of the FCC
rules specifies electromagnetic interference
(EMI) from lighting devices operating at
frequencies greater than 9 kilohertz (kHz).
Typical electronically-ballasted compact
fluorescent lamps operate in the 24 - 100 kHz
frequency range.
Field Angle
The angular dimension of the cone of light from
reflectorized lamps (such as R and PAR types)
encompassing the central part of the beam
out to the angle where the intensity is 10% of
maximum (See BEAM ANGLE).
Filament Design
Filaments are designated by a letter
combination in which C is a coiled wire filament ,
CC is a coiled wire that is itself wound into a
larger coil, and SR is a straight ribbon filament .
Numbers represent the type of filament-
support arrangement .
Fixture Requirements
Describes fixture requirements for HID lamps.
O = Open or Enclosed Fixtures
E = Enclosed Fixtures Only
S = Lamps operated in a vertical position (Base
Up or Down) ±15º, can be used in an open
fixture. Lamps burned in any other orientation
must be used in “enclosed fixtures only”.
Flicker
The periodic variation in light level caused by AC
operation that can lead to strobe effects.
Flood
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”)
Floodlight
A luminaire used to light a scene or object to
a level much brighter than its surroundings.
Usually floodlights can be aimed at the object
or area of interest .
Fluorescence
A physical phenomenon whereby an atom of a
material absorbs a photon of light an immediately
emits a photon of longer wavelength. If there
is a significant delay the phenomenon is called
phosphorescence rather than fluorescence. It is
interesting that “phosphors” used in lamps exhibit
“fluorescence,” not “phosphorescence.”
(See PHOSPHOR).
Fluorescent HO
Fluorescent HO and VHO lamps require special
ballasts that generate higher currents than
standard ballasts and operate the lamps at
higher wattage than standard lamps. These
lamps are generally less efficient than the
standard product . Metal Halide HO and
XHO lamps operate on the same ballasts as
standard lamps and at the same wattage but
are more efficient and produce higher light
output than standard lamps.
Fluorescent Lamp
A high efficiency lamp utilizing an electric
discharge through low pressure mercury
vapour to produce ultraviolet (UV) energy. The
UV excites phosphor materials applied as a thin
layer on the inside of a glass tube which makes
up the structure of the lamp. The phosphors
transform the UV to visible light .
Footcandle (fc)
A unit of illuminance or light falling onto
a surface. It stands for the light level on a
surface one foot from a standard candle. One
footcandle is equal to one lumen per square
foot . See also Lux.
Footcandle Meter
(See ILLUMINANCE METER).
Footlambert
An obsolete term referring to a luminance of 1/?
candelas per square foot .
Forward Current
Current through an LED in the direction of its
greatest conduction.
Forward Voltage (VF)
The voltage across an LED for a given forward
current .
Four-Pin Compact Fluorescent Lamps
A “plug-in” compact fluorescent lamp with 4
pins in the base to make electrical contact with
the ballast . Four-pin lamps can be dimmed on
appropriate dimming ballasts while two-pin
lamps cannot .
Frequency
Rate of alternation in an AC current . Expressed
in cycles per second or Hertz (Hz).
Fovea, Foveal Vision
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 (See PHOTOPIC, SCOTOPIC,
EYE SENSITIVITY).
Full Spectrum Lighting
A marketing term, typically associated with
light sources that are similar to some forms of
natural daylight (5000K and above, 90+ CRI),
but sometimes more broadly used for lamps
that have a smooth and continuous colour
spectrum.
G
Genura™
GE’s electrodeless compact fluorescent
lamp, Genura™, uses induction to power the
discharge. The chamber generates UV (just
like a discharge in a regular fluorescent lamp)
that is converted by phosphors to visible light .
Because Genura™ uses no electrodes, the life
of this unique reflector lamp is longer than
typical compact fluorescent products (see
INDUCTION LIGHTING).
Glare
Visual discomfort caused by excessive
brightness is called discomfort glare. If task
performance is affected it is called disability
glare. Glare can be direct glare or indirect
(reflected) glare (See VEILING REFLECTIONS and
VISUAL COMFORT PROBABILITY).
Group Relamping
The practice of replacing all the lamps at an
installation at one time with new lamps when
the lamps have operated for (typically) 65%
to 70% of rated life. The two benefits of group
relamping are: (1) reduced maintenance costs
because of the expense and inconvenience of
replacing failing lamps one at a time, and (2)
improved appearance and performance since
older lamps are often degrading in brightness
and colour as they age.
H
Halogen Lamp
A halogen lamp is an incandescent lamp with
a filament that is surrounded by halogen
gases, such as iodine or bromine. Halogen
gases allow the filaments to be operated at
higher temperatures and higher efficacies. The
halogen participates in a tungsten transport
cycle, returning tungsten to the filament and
prolonging lamp life.
Halogen-IR (HIR™) Lamp
GE designation for high-efficiency tungsten
halogen lamps. HIR lamps utilize shaped
filament tubes coated with numerous layers of
materials that transmit light but reflect the heat
(infrared) back into the filament . This reduces
the power needed to keep the filament hot .