Electric light source such as an incandescent lamp, discharge lamp or LEDs. In a luminaire, the light source produces light which can then be directed to the target objects via reflectors.
Component of the lamp through which the electrical connection to the lampholder of the luminaire is made.
Lamp designation system
Uniform system for naming electric lamps. The abbreviation of a lamp includes information on the method of light generation, the bulb material or gas fillings, the wattage and the type of lampholder.
The functional life of a lamp. The functional life of incandescent lamps is based on the failure of 50% of the lamps. The functional life of discharge lamps and LEDs is calculated at the point when the installation´s luminous flux drops to 50% due to failed lamps and reduced luminous flux.
Lamp lumen maintenance factor
Calculation value for the maintenance plan of a lighting system which considers the drop in luminous flux due to the lamp aging.
Lamp survival factor
Calculation value for the maintenance plan of a lighting system which considers the deviation in the life of individual lamps from the average lamp life and/ or premature lamp failures with fixed maintenance cycles.
Bracket used to hold the lamp in a luminaire and to make the electrical connection. Typical lampholder types are screw-thread, bayonet fixing and bi-pin base. The type of lampholder for each lamp is documented in the Lamp designation system.
Abbreviation for Local Area Network. A permanently installed local computer network over short distances.
Abbreviation for Low-loss Control Gear.
Abbreviation for Lamp designation system
Leading edge technology
Method of dimming in which the power consumption of the lamps is limited by the leading edge of the alternating current wave. With leading edge technology, the current is switched on with a delay after the alternating voltage passes through the zero point and remains switched on until the next zero crossing. Dimmers with leading edge technology are not usually suitable for conventional or compact fluorescent lamps. Leading edge technology is used to control conventional control gear.
Abbreviation for Light Emitting Diode. An electroluminescent radiator that produces light by recombining chargecarrier pairs in a semiconductor. LEDs produce a narrow-band spectral range. White light is obtained by RGB mixing or luminescence conversion.
Optical element used for light guidance. The radius, curvature and surface texture of the lens determine its optical properties. With projector spotlights, lens systems can be used to precisely project images and patterns from gobos. Fresnel lenses can be fitted into spotlights as an accessory in order to spread the light either symmetrically or asymmetrically.
Luminaires with asymmetric light intensity distribution for uniform wall lighting. The light is spread by a lens.
The term for a beam of light, usually from a rotationally symmetrical reflector. The luminaire´s optical system determines whether the gradient of the edge of the beam is abrupt or gradual. With spotlights, the beam can be freely aimed by rotating and tilting the luminaire.
Light beam diameter
The diameter of a light beam results from the emission angle and the distance to the luminaire.
The colour of the light emitted by a lamp. The colour of light can be expressed by using xy coordinates to specify a colour locus in the chromaticity diagram. White light colours can also be expressed as a colour temperature, and can also be broadly categorised as either warm white (ww), neutral white (nw) and daylight white (dw). The same colours of light can have different spectral distributions and a correspondingly different colour rendition.
Light control (1)
Light guidance by means of reflectors or lenses is used in luminaires with defined optical properties to produce luminaires. Light guidance is crucial for visual comfort. The glare of luminaires can be reduced to a permissible level by controlled light guidance.
This describes the degree to which a material will be damaged by exposure to light. It primarily applies to changes in the colour of the material (colour fastness), but may also apply to the material itself.
Light loss factor
Reciprocal value of the maintenance factor. When designing an installation, this takes the overall light loss effect of lamp ageing, lamp failure and general dirt accumulation into consideration. The new value of illuminance is higher than the maintenance factor by an amount equal to the light loss factor.
Light output ratio
The light output ratio is the ratio of emitted luminous flux to the lamp lumens produced in the luminaire. It is abbreviated as LOR.
Term used for light emission which, due to its illuminance, its direction or its spectrum, causes interference in any particular situation. In outdoor areas, light pollution refers to light which is emitted into the night sky reducing the darkness. The consequences include wasted energy and a detrimental effect on flora and fauna. The avoidance of light pollution is also known as Dark Sky in terms of lighting design.
The limiting of intensity, ultraviolet radiation and infrared radiation, required especially in relation to exhibition lighting. Light protection is implemented by choosing suitable lamps and luminaire types and by filtering the emitted light.
A lighting situation or a lighting mood with a specific combination of brightness levels and colours. Light scenes can be saved and then recalled either automatically or manually using a lighting control system.
A series of several consecutive light scenes. Dynamic scenic lighting is produced by defining the sequential order of light scenes, their duration and the transitions between the scenes using a lighting control.
Arrangement of individual luminaires connected to form a predominantly linear framework which is usually suspended from the ceiling.
Local Operating Network
Bus system for communication between installations and devices, for example, for building control systems.
Abbreviation for Local Operating Network
Low-pressure discharge lamp
This category includes conventional fluorescent lamps and compact fluorescent lamps.
Low-voltage halogen lamp
A highly compact tungsten halogen lamp which operates on low voltage (usually 6, 12 or 24 V). Frequently fitted with an integrated metal reflector or coolbeam reflector.
Unit of luminous flux
An object containing a lamp and providing artificial illumination. The lamp is held in the lampholder. Reflectors provide light guidance. Luminaires can be permanently installed as surface-mounted, recessed, pendant or free-standing luminaires or track-mounted, which can be variably positioned and aimed.
The photometric classification is made using the luminous intensity distribution curve and light output ratio, and also the type of lamp and maximum lamp power; the safety classification is made using the protection mode and protection class.
Luminaire for linear light source
Common term for long rectangular luminaires fitted with fluorescent lamps (linear fluorescent luminaires), usually designed with low-brightness louvres.
Luminaire maintenance factor
A calculation factor determined by the maintenance plan of a lighting installation which considers the drop in luminous flux due to the luminaire design and the reduction in luminaire performance.
Luminaires for pictograms
The design of pictogram luminaires usually matches standard directive luminaires and safety signs; pictograms are edge-lit or backlit.
Unit: candela/m2 (cd/m2).
The luminance describes the brightness of a surface that emits light either as a light source or by transmission or reflection. The luminance is defined as the ratio of light intensity to the surface projected perpendicular to the direction of observation. Differently coloured surfaces with the same luminance are equally bright.
Collective term for all forms of light not created by thermal radiators (photo-, chemo-, bio-, electro-, cathodo-, thermo- or triboluminescence).
Conversion from one spectrum to another by using phosphors.
This technique is used with LEDs or fluorescent lamps to convert ultraviolet radiation into visible light.
Unit: Lumen/Watt (lm/W)
The luminous efficacy is defined as the ratio of the emitted luminous flux to the expended electric power of a lamp.
Unit: Lumen (lm)
The luminous flux expresses the total light power emitted by a light source. It is calculated from the spectral radiant power by evaluating this with the spectral brightness sensitivity of the eye.
Unit: candela (cd)
The light intensity is the luminous flux per solid angle (lm/sr). The spatial distribution of the light intensity of a light source is shown by the light intensity distribution curve.
Luminous intensity distribution curve
The light intensity distribution curve is obtained by taking a section through the light intensity distribution, which represents the light intensity of a light source for all solid angles. With rotationally symmetrical light sources, the luminous intensity distribution can be shown by a single light intensity distribution curve, whereas two or more curves are required for axially symmetrical light sources. The light intensity distribution curve is generally expressed in the form of a polar coordinate diagram, but with projectors it is often shown in Cartesian coordinates.
Another term for luminous flux; in radiation physics, it is equivalent to the radiant power.
Unit of illuminance