Simple explanations in plain language of technical terms often used in the lighting industry

1. Lighting Jargo
De-mystified

2. A simple guide to w
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3. Lighting jargon de-mystified
BALLAST
In a fluorescent lighting system, the ballast regulates the
current to the lamps and provides sufficient voltage to
start the lamps.
B
Without a ballast to limit its current, a fluorescent lamp
connected directly to a high voltage power source would
rapidly and uncontrollably increase its current draw.
Within a second the lamp would overheat and burn out.
During lamp starting, the ballast must briefly supply high
voltage to establish an arc between the two lamp
electrodes. Once the arc is established, the ballast
quickly reduces the voltage and regulates the electric
current to produce a steady light output.
Breeam rating
Breeam stands for the Building Research Establishment
Environmental Assessment Method and it’s the industry’s leading
environmental rating system for buildings. More than 200,000
buildings have been assessed and awarded a Breeam rating.
Breeam evaluates design, construction and use.

4. Lighting jargon de-mystified
CANDELA
C
A candela is the luminous intensity
emitted by a light source in a particular
direction weighted by the sensitivity of
the human eye to different wavelengths.
One candle has an approximate intensity
of one candela.
Ceramic lamps
Ceramic metal halide (CMH) lamps combine
high output with great colour rendering and
good efficiency. They produce light by passing
an electric arc through a mixture of gases. In a
metal halide lamp the compact arc tube contains
a high-pressure mixture of argon, mercury and a
variety of metal halides.
CFL
Popularly referred to as energysaving lamps, compact fluorescent
lamps have a poor image because of
perceived deficiencies in colour,
power and the time it takes for
them to reach full output. But
massive improvements have been
made in all these areas thanks to
substantial investment by the big
lamp manufacturers.

5. Lighting jargon de-mystified
CHROMATICITY
Colour temperature
Chromaticity is an
objective specification of
the quality of a colour
regardless of its luminance
as determined by its hue
and colourfulness. It is the
quality of a colour or light
with reference to its purity
and its dominant
wavelength.
Colour temperature describes whether a light source
appears ‘warm’ or ‘cool’ – indicated by the correlated
colour temperature (CCT). Lamps with a warm
appearance have a CCT of 2700-3000K and are considered
appropriate for domestic settings; cooler lamps might be
4000K and are used more often in offices and shops.
C
CRI
Short for colour-rendering index, CRI is
the ability of a light source to show the
colours of objects accurately. The higher
the CRI on a 1-100 scale, the more
accurately the lamp will render colours.
Lamps with poor colour rendering will
distort some colours. CRI only works for
approximately white sources and
doesn’t actually tell you which colours a
light source renders well or badly.

6. Lighting jargon de-mystified
DALI
The Digital Addressable Lighting
Interface is a protocol for lighting
controls and dimming agreed by
major manufacturers. It is set out
in the technical standard IEC
62386 and promoted by a Dali
working group set up by
manufacturers and institutions.
D

7. Lighting jargon de-mystified
Efficacy
Specific luminous efficacy indicates the efficiency
with which electrical energy is converted to light, i.e.
how much luminous flux is produced using electric
input power (W) supplied to the light source. The
unit is lumen per watt (lm/W).
E

8. Lighting jargon de-mystified
Fluorescent lights
A fluorescent lamp or tube is a
very low pressure mercury-vapour
gas-discharge lamp that uses
fluorescence to produce visible
light. The electric current (in the
gas) excites mercury vapour
which produces short-wave
ultraviolet light that then causes a
phosphor coating on the inside of
the bulb to fluoresce, producing
visible light.
The luminous efficacy of a
compact fluorescent light bulb is
about 60 lumens per watt, four
times the efficacy of a typical
incandescent bulb.
For conventional tube fluorescent
lamps the fitting is more costly
because it requires a heavy
ballast to regulate the current
through the lamp, but the lower
energy cost typically offsets the
higher initial cost.
F

9. Lighting jargon de-mystified
HEAT SINK
Heat sinks are used with high-power semiconductor devices such as light
emitting diodes (LEDs), where the heat dissipation ability of the basic device is
insufficient to moderate its temperature. A heat sink is designed to maximize
its surface area in contact with the cooling medium surrounding it, such as the
air. In general, the more surface area a heat sink has, the better it works,
hence many of them feature arrays of fins.
Halogen light
The halogen lamp is also known as a quartz halogen and
tungsten halogen lamp. It is an advanced form of
incandescent lamp. The filament is composed of ductile
tungsten and located in a gas filled bulb just like a
standard tungsten bulb, however the gas in a halogen
bulb is at a higher pressure (7-8 ATM). The glass bulb is
made of fused quartz, high-silica glass or aluminosilicate.
This bulb is stronger than standard glass in order to
contain the high pressure. This lamp has been an
industry standard for work lights and film/television
lighting due to compact size and high lumen output.
H

10. Lighting jargon de-mystified
HID
High-intensity discharge lamps (HID lamps) are a type of
electrical gas-discharge lamp which produces light by means
of an electric arc between tungsten electrodes housed
inside a translucent or transparent fused quartz or fused
alumina arc tube. Varieties of HID lamp include:
Mercury-vapour lamps
Metal-halide (MH) lamps
Ceramic MH lamps
Sodium-vapour lamps/high pressure sodium
Xenon short-arc lamps
H

11. Lighting jargon de-mystified
Incandescent
An incandescent light produces light with a filament wire heated to a high
temperature by an electric current passing through it, until it glows. The hot
filament is protected from oxidation with a glass or quartz bulb that is filled
with inert gas or evacuated. The light bulb is supplied with electrical current by
feed-through terminals or wires embedded in the glass.
Most bulbs are used in a socket which provides mechanical support and
electrical connections. Incandescent bulbs are much less efficient than most
other types of electric lighting and convert less than 5% of the energy they use
into visible light – they’re really heaters that give off light as a by-product.
I

12. Lighting jargon de-mystified
Induction lighting
Induction lighting is a form of light created by filling
the inside of a bulb with mercury gas and exciting it
with electricity. When this excitation occurs, ultra
violet radiation is emitted that then converts into
visible light. The phosphor coating inside the bulb
determines the colour of light that is emitted. Since
induction lamps do not contain electrodes, which
can eventually burn out, they last much longer than
fluorescent lamps.
IP rating
An IP (index of protection) rating tells
you the level of protection that a
luminaire or other piece of equipment
provides against things getting in –
including dust, dirt and water as well as
hands and fingers. For example, a
fitting rated IP22 is protected against
insertion of fingers and will not be
damaged by exposure to dripping
water.
I

13. Lighting jargon de-mystified
K
Kelvin
The light colour of a light source determines the
atmosphere in the room. It is defined by the colour’s
temperature of artificial light source, expressed in
Kelvin (K). Low temperatures create warm lighting,
high temperatures, in turn, create a colder-looking
environment.
kWh
The kilowatt-hour is a
unit of energy equal to
1,000 watt-hours.
That’s what a 1,000W
device uses in one hour
– or what a 1W device
uses in 1,000 hours. It’s
the ‘unit’ that shows up
on your electricity bill.

14. Lighting jargon de-mystified
Li-Fi
L
Light fidelity is visual light
technology that uses light
from LED luminaires to
transmit data. It uses
invisible modulations in the
light from the LED fittings
to provide a fast, reliable
wireless internet
connection.
Lux
Lux is the international unit
of illuminance – a measure
of how much luminous flux
(in lumens) is spread over a
given area (in square
metres). In other words, it
tells you how much light is
hitting a surface. 1lm/m2
equals 1lx.
L70
L70 is a term used to specify a lumen
maintenance factor for a light source.
Lumen maintenance compares the
amount of light emitted by a source
when it is new with the amount
emitted at a specific time in the
future. The L70 figure is the time
taken for the light emitted by the
source to drop to 70 per cent of its ‘as
new’ value. L50 and L80 are also used
within the lighting industry.

15. Lighting jargon de-mystified
LED
Light emitting diodes (LEDs) are based on solid-state semiconductor technology and are the most efficient white light
source. Having no air, glass or fragile filaments, LEDs are
extremely resistant to shock and vibration. They deliver big
energy savings, good colour rendering, dimmability and a
long life which reduces maintenance needs.
L
LED driver
LIGHT ENGINE
An LED light engine is a combination of one or more LED
modules together with the associated electronic control
gear (ECG), also known as an LED driver. An LED module
contains one or more LEDs, together with further
components, but excluding the ECG.
An LED driver is a self-contained power
supply that has outputs matched to the
electrical characteristics of your LED or
array of LEDs. There are currently no
industry standards, so understanding
the electrical characteristics of your
LED or array is critical in selecting or
designing a driver circuit. Drivers should
be current-regulated (deliver a
consistent current over a range of load
voltages).

16. Lighting jargon de-mystified
Leni
The Lighting Energy Numeric Indicator – a measure
of the energy predicted to be used by the lights in a
building, taking into account daylight, occupancy,
operating hours and controls. Leni is much more
nuanced as a predictor of energy use than simply
measuring the efficiency of luminaires. Leni knows,
for example, that a building in John O’Groats will
have to use a little more lighting energy than an
identical building at Land’s End, because the
availability of daylight will differ.
LOR
Light output ratio – the percentage of
light emitted from the light source that
makes it out of the luminaire. A LOR of
70 means 30 per cent of the light from
the lamp is lost inside the reflector and
light fitting. There is some debate about
how to apply LOR to LED luminaires
because of the directional nature of the
light they emit.
Lumen
The lumen is the international unit of luminous flux. One lumen is
the amount of light emitted per second in a solid angle of one
steradian from a one candela light source. (A steradian is a solid
angle at the centre of a sphere subtending a section on the surface
equal in area to the square of the radius of the sphere.)
L

17. Lighting jargon de-mystified
METAL HALIDE
A metal halide lamp is a type of highintensity discharge lamp that produces light
by an electric arc through a gaseous mixture
of vaporised mercury and metal halides.
Metal halide lamps have high luminous
efficacy of around 75 - 100 lumens per watt
(about twice that of mercury vapour lights
and 3 to 5 times that of incandescent lights)
and produce an intense white light.
Mercury Vapour
The mercury vapour lamp is a high intensity discharge
lamp. It uses an arc through vaporised mercury in a high
pressure tube to create very bright light directly from its
own arc. While it has good efficiency and better colour
rendering than HPS street lights which have a better lm/w
rating, the lamp requires a warm-up time to start and even
then produces a greenish tinge.
M

18. Lighting jargon de-mystified
OLED
Short for organic light-emitting diode, a display device that sandwiches carbon-based
films between two charged electrodes, one a metallic cathode and one a transparent
anode, usually being glass. When voltage is applied to the OLED cell, the injected
positive and negative charges recombine and create electro luminescent light.
It is beginning to replace LCD technology in handheld devices such as PDAs and cellular
phones because the technology is brighter, thinner, faster and lighter than LCDs, uses
less power, offers higher contrast and is cheaper to manufacture.
O

19. Lighting jargon de-mystified
PIR
Short for passive infrared, PIR sensors are electronic sensors that measure infrared light
radiating from objects in their field of view. Sometimes known as proximity sensors, they can
detect heat from objects that is undetectable by mere humans. When combined with lighting
they can be used to deliver the light only when needed, for example, with street lights which
would otherwise be in full use throughout the night even when there is no one in the vicinity.
P

20. Lighting jargon de-mystified
SON
High pressure sodium lamps (commonly called SON lamps) are gas discharge
lamps that use sodium vapour in an excited state to produce light. They are
often used for street lighting. SONs produce a yellow light and have poor colour
rendering, but they are efficient, often reaching efficacies of about 100lm/W.
Higher-powered 600W versions can reach an efficacy of 150lm/W.
S

21. Lighting jargon de-mystified
White light
W
White light is the name given to what the human eye
sees when all the colours that make up the visible light
spectrum are combined. Incandescence, which is visible
light created from heat, is the greatest known generator
of white light. Objects with lower temperatures emit
infrared radiation, which cannot be seen, but as an
object gets hotter, the wavelengths get shorter and
brighter, moving through red to yellow to white; these
white lights are visible to the human eye. In addition to
the sun and the common light bulb, molten materials,
such as metal or glass, also glow incandescently.
WEEE
Waste electrical and electronic equipment.
This includes old fridges and fax machines
as well as lamps and luminaires. An EU
directive defines WEEE and sets out how
you are and aren’t allowed to dispose of it.
Recycling schemes such as Lumicom and
Recolight help manufacturers of lighting
products comply.

22. Lighting jargon de-mystified
XENON
A xenon arc lamp is a specialised type
of gas discharge lamp that produces
light by passing electricity through
ionised xenon gas at high pressure. It
produces a bright white light that
closely mimics natural sunlight.
Xenon arc lamps are used in movie
projectors in theatres, in searchlights
and for specialised uses in industry and
research to simulate sunlight.
In order to achieve maximum efficiency,
the xenon gas inside short-arc lamps is
maintained at an extremely high
pressure — up to 30 atmospheres (440
psi / 3040 kPa) — which poses safety
concerns. As lamps age, the risk of
failure increases, so bulbs being
replaced are at the greatest risk of
explosion. Because of the danger, some
lamps, especially those used in IMAX
projectors, require the use of full-body
protective clothing.
X

23. Lighting jargon de-mystified
Zhaga
Z
Zhaga (not an acronym) is an industry-wide co-operation
to standardise specifications for the interfaces of LED
light engines. The aim is to enable interchangeability
between products made by diverse manufacturers by
defining interfaces for a variety of application-specific
light engines. Currently all Zhaga members are
manufacturers.
ZIGBEE
ZigBee is a global specification for
digital radio communication that is
suitable for applications that require a
low data rate, long battery life and
secure networks. Among those
applications is lighting control. No
special devices are needed to connect
equipment to the lighting network.
ZigBee is simpler and cheaper to
implement than other wireless
networks such as Bluetooth.