E
F
G
can control up to 512 separate devices.
Since DMX only supports 512 channels, there
may be situations where separate DMX
universes are needed. A DMX universe is a single
line connecting the controller and all the devices
associated with that cable. Most recent DMX
consoles support more than one DMX universe,
each of which must be wired independently.
A DMX cable is made up of at least three poles
for the transmission of signals.
Downlight
Device with direct emission, generally mounted
in plasterboard ceilings.
It is used in corridors (where no glare control
is needed) and in workplaces (where conformity
to standard UNI 12464 with regard to direct
glare and glare on video terminals must be
ensured). They are usually installed in the room
in a regular grid so that the lights are spaced
evenly at 1.8 x 1.8 metres or 2.4 x 2.4 metres.
Efficacy
Ratio between the luminous flux of a lighting
device and its power in watts. It is expressed
in lumen/W.
Efficiency
Optical output; percentage ratio between
the output luminous flux of the light fitting
and the flux emitted by the light source.
(See LOR)
Electrical connector
An electrical connector such as an electrical
component, or an area of a printed circuit
board, whose function is to electrically connect
two or more electrical components exclusively
by means of operations of a mechanical type
(therefore without requiring electric welding).
Electrified track
Power supply system with voltage or low
tension. Electrical conductors are located inside
the track.
Electromagnetic wave
Electromagnetic energy carrier in single packs
or ‘quantums’ of energy, with a defined energy
value. It moves in a straight line at approximate
300,000 Km/s. It has associated magnetic
and electrical fields varying in time following
a sine law.
Elliptical reflector
Ellipsoidal mirror (rotational or not) that, with
a light source on the first focus, can replicate
its image on the second focus (if rotational
ellipsoid) or on a specific area of the optical axis
(if non rotational ellipsoid).
Emergency lighting
Lighting intended for use when a general
lighting system fails due to a power failure.
Dialux
Light design software. Used to obtain
all types of lighting calculations and related
documentation in accordance with the legal
regulations in force in various countries,
as well as visualisations and animations
for a realistic rendering of a project.
Diaphragm
element modulating the amount of luminous
flux passing through an optic system.
A so called ‘vignetting’ phenomenon takes place
if openings of other elements interfear with
the above.
Diffraction
Deviation of the direction of propagation
of radiation, determined by its wave nature,
which occurs when the waves are restricted
by obstacles.
Diffused lighting
Lighting in which the light on the work
surface or on an object does not come from
any particular direction.
Diffuser
Optical element, transparent or opaque,
able to diffuse its incident light rays in the
surrounding space.
Diffusion
Phenomenon whereby the spatial distribution
of a beam of radiation changes when the beam
is deflected in multiple directions, by a surface
or a medium, without changes of frequency
in its monochromatic components.
Dimmable
Light fittings that can adjust their light intensity.
Direct glare
Glare produced by light sources
in the visual field.
Direct lighting
Lighting by devices that distribute the light
intensity in such a way that 90-100% of the
luminous flux goes directly onto the work
surface, assuming that this surface is not infinite.
Dispersion
The white light that falls on the face of a prism,
is dispersed and flows out from the opposite
face with the spectral components separated.
This occurs because the index of refraction
of a given material is a function of wavelength
and therefore different colours (different
wavelengths) are refracted at different angles.
DMX
DMX512, often abbreviated DMX (Digital Multi-
pleX) is a communications protocol used mainly
to control scene lighting [and] for control from
computers or central units of complex lighting
systems with moving or conventional lights.
Each DMX512 cable can transmit up to 512 8-bit
values between 0 and 255, so that a cable
Emission angle
See Beam.
EN 12464
Standard that defines lighting technology
features such as average illumination,
uniformity, colour rendering and UGR
for interiors. This standard also defines the
maximum luminance of a device to be used in
environments where there are video terminals.
Field of Vision
Of the eye or eyes. Angular width of the space
in which an object can be when the observer
looks at an object directly in front of him.
The field can be monocular or binocular.
Filter
Optic element that can totally or partially select
the wave lengths of a light source spectrum.
In case of a total selection (net cut of the wave
lengths between certain values), it is called
a bandpass filter.
Flood
Term to identify a 2 ½ theta opening between
15 and 20° in a projector.
Fluorescent source
Discharge lamp of the low pressure mercury
type in which most of the light is emitted
by a layer of fluorescent material excited
by the ultraviolet radiation of the discharge.
Fresnel lens
Element allowing construction of large optics
and small focal distance without the obstruction,
the thickness and the weight of the material
used to produce a spheric conventional lens of
equivalent diottric power. The result is obtained
dividing the spheric lens into a series of concentric
circular sections, called Fresnel rings. For each zone
the thickness of the lens is limited, while the conti-
nuous curve is transformed into a series of surfaces
of non-continuous with the same curvature.
General Lighting
Essentially uniform lighting of an area
or a volume that does not take into account
specific local needs.
Glare
Visual condition in which there is discomfort
or reduction of vision, caused by an unsuitable
distribution or degree of brightness or too much
contrast in space and time.
Goniophotometer
Instrument for the measurement of photometric
magnitudes, for measuring the angular
distribution of a magnitude of brightness
emitted by a light source, a lighting fixture,
a medium or a surface.
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