Accuracy (of measurement)
Approximate agreement between the result
of a measurement and the actual value of the
item being measured. It is a qualitative term:
the term “precision” should not be used
as a synonym.
Active cooling
System composed of one or more radiators
made of a conductive materials, plus a fan or
another element conveying air on the radiator.
Adjustable dowsers
Adjustable, removable partitions applied on
a projector, able to screen its light as required.
Ampere (A)
The SI base unit used to measure the intensity
of electric current.
Angle of inclination
Angle of inclination calculated upward
from the horizontal of a lighting fixture.
Anti-dazzle grid
Element usually with square or hexagonal grid
(other geometric shapes could be applied) able
to cut unrequired, dazzling light rays that can
cause glare. Its finish is usually black or alumi-
nium. The shaped section allows the reflected
light to be deviated towards specific angles,
so that the dazzle effect is removed.
Asymmetric lens shield tube
Accessory located in front of a projector,
able to cut unrequired, dazzling light rays
that can cause glare.
Axial intensity
Lighting intensity emitted by any lighting device
on its own main axis.
Backup Lighting
Part of the emergency lighting provided
to ensure that an exit can be identified
efficiently and used if the normal lighting system
does not work.
Beam
in a projector, or in a rotosymmetrical / X-Y
type device, it is double the angle made by
the direction of the axial luminous intensity and
the direction where intensity is ½ of the axial.
BIN
A term used in the LED industry to define
selections of: Colour (the BIN defines a variable
area of the chromaticity diagram). Luminous Flux
(the BIN defines the amount of luminous flux
emitted). Vf (the BIN specifies the maximum
and minimum values of the voltage drop applied
across the LED terminals).
Black body
It is an ideal object absorbing all incident
electromagnetic radiations. Being black, it is
neither reflecting nor transmitting any energy.
The black body produces electromagnetic
radiation as a consequence of its temperature.
Artemide Dictionary of Light
Candela
SI unit of luminous intensity: the candela (cd)
is the luminous intensity, in a given direction,
of a light source that emits monochromatic
radiation at a frequency of 540 THz and whose
energy intensity in that direction is equal
to 1/683 W per steradian.
Candela per square metre (m-2)
SI unit of luminance.
Catadiottric optic
Optical system usually mixed (refractive
+ reflective) on which reflection takes place,
both because of the TIR principle and because
of the use of mirrors.
CCT
Acronym of Correlated Color Temperature.
It is expressed by the colour temperature in Kelvin
degrees of a specific colour while in proximity
of the black body curve in the different cromatic
diagrams.
Cd/klm
Measurement unit of the luminous intensity.
It is expressed in candles and is referred to the
luminous flux installed, expressed in Kilo lumens.
Chromatic Rendering Index
Index evaluated by the ability to render a series
of 14 colours, chosen using Munsell chromatic
system, compared to a reference source
depending on the colour temperature.
If the colour temperature is below 5,000K,
the reference source is the black body spectrum
with the same colour temperature. If the CRI
is higher, then the chosen reference source is
a series D illuminant with colour temperature
similar to the one of the source chosen.
Chromaticity diagram
Plane diagram in which the points, defined
by the respective trichromatic coordinates,
represent the chromaticity of colour stimuli.
Cold white
White colour of a light source with colour
temperature greater than 5000 Kelvin.
Collimation lens
A lens directing the light rays incident on itself
to the parallel optical axis of the lens itself.
Color temperature
It is the temperature of the black body produ-
cing a spectral emission with chromatic features
similar to the source itself. The colours emitted
by heating the black body are, starting from
the lowest temperatures, red (up to 1,800K),
orange (between 1,800 and 2,200K), warm
white (between 2,200 and 3,500K), neutral
white (between 3,500 and 5,000K), cold white
(from 5,000K to infinity).
Color tolerance
Color difference inside a chromatic section
of a lighting source (e.g. LED), usually produced
by the manufacturer and identified with
an acronym.
Colourimetry
Measurement of colours, based on a set
of conventions.
Connector
Connecting element between two components
of a system. It can be mechanical, electrical
or electronic.
Cones
Photoreceptors of the retina containing
pigments that are flexible in light which
are the basis of the photopic vision process.
Constant current
See also definition of ‘current’. Current supplied
by an electrical device that is kept at a constant
level. Constant current power supplies distribute
a specific current within certain tension limits.
These can vary from zero to a maximum value,
or from a minimum to a maximum value.
Constant tension
See also definition of ‘tension’. Tension supplied
by an electrical device, kept at a constant level
until its maximum power level is reached.
Contrast
Subjective adjustment of the difference
in appearance of two parts of a visual field
(observed simultaneously or in succession).
Current
Electrical charge flux (usually negative)
passing through a surface during a time unit.
It is a fundamental magnitude in the International
System. It is measured in Ampere.
Cut off
In a photometric solid, it is the angle or the
angles in which a net distinction between light
and dark can be perceived. It is calculated
in respect to the main axis of the device.
Dali
Digital Addressable Lighting Interface.
Protocol managing a system of light fittings
through a signal transmitted by a single
pair of wires. The DALI system can manage
single or groups of light fittings included
in the same system. Also, it can switch
on and off and create scenaries with light
fittings belonging to a same system.
Dali-SwitchDim
Compactibility of the power supply to work
on a DALI protocol only or also through the
SwitchDim function. In this last case, the load
dimming is made through a simple push-to-
make switch at the supply voltage.
Dark light
Device showing a luminance lower than
3,000 cd/m2 in every ‘C’ plan for ‘gamma’
values equals or higher than 65°. It is calculated
in respect to the main axis of the device.
This value was originally 1,000 cd/m2, now
it is increased to 3,000 cd/m2 for most devices.
A
B
D
C
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