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Technical environment
Technical environment
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Glossary 4014


  • Absorption
    The ability of substances to neither reflect nor transmit light. Its dimension is the absorption ratio, which is defined as the ratio of absorbed luminous flux to incident luminous flux.

  • Accent lighting
    Emphasis given to individual areas of a space or to individual objects by specific lighting at a level above that of the ambient lighting.

  • Accommodation
    Adaptation of the eye to enable objects at different distances to be seen in sharp focus. It is performed by deforming the eye lens.

  • Adaptation
    The ability of the eye to adjust to the luminances in the field of vision. Performed initially via the dilation or contraction of the pupils, though a far greater scope is achieved by altering the sensitivity of the retina´s receptor cells and by changing between vision with cone cells and vision with rod cells (see also Eye).

  • Adapter
    A device for connecting a luminaire, especially a spotlight or floodlight, both mechanically and electrically to a track.

  • Additive colour mixing
    Refers to the mixing of colours by the addition of spectral ranges. According to the trichromatic theory, the colours produced by additive colour mixing are the complementary colours of the primary colours (red, green and blue). Mixing the three primary colours in equal amounts produces white light.

  • Ambient luminescence
    Ambient luminescence provides general lighting for the surrounding area. It ensures that architecture and the objects and people in it are visible. It allows the occupants simply to get their bearings, work and communicate.

  • Anti-dazzle cap
    An anti-dazzle attachment for controlling of light from the lamp in the beam direction of the luminaire. The beam is restricted in the main direction of the beam and the spill light components are reduced and/or prevented completely.

  • Anti-dazzle screen
    Anti-dazzle attachment to improve visual comfort. The cross baffle partially conceals the reflector and the lamp.

  • Anti-glare protection
    Solar protection

  • Architectural lighting
    Term given to lighting concepts using both daylight and artificial light, whereby the technical solution is an integral constituent part of the architecture.

  • Backlighting
    Type of lighting which is projected from behind the object and casts shadows forward. It can result in a halo of light being visible around the object. In stage lighting, backlighting is used for dramatic lighting effects.

  • Barn doors
    Term given to anti-dazzle plates arranged in a square around the luminaire to reduce the direct glare; typically found on stage lighting projectors.

  • Beam spread
    Emission angle

  • Brilliance
    Lighting effect on reflective surfaces or transparent materials. Brilliance is produced by the reflection of the light source or the refraction of light; it requires directed light from point light sources.

  • C.I.E. standard colourmetric system
    System for the numerical classification of colours of light and body colours. The chromaticity diagram is a two-dimensional diagram in which the colour loci of all colours and colour mixes are represented in grades of saturation ranging from the pure colour through to white, which can be numerically expressed by their xy coordinates. Colour mixes are located on a straight line drawn between the colours to be mixed; the colour of light of thermal radiators lies on the defined curvature of the Planckian curve.

  • Candela, cd
    Unit of light intensity; fundamental dimension of lighting engineering. 1 cd is defined as the light intensity emitted by a monochromatic light source with a radiant power of 1/683 W at 555 nm.

  • CCG
    Abbreviation for Conventional Control Gear

  • Ceiling washlight
    Luminaire type which is mounted individually or in rows above eye-level in or on walls. These luminaires illuminate the ceiling area uniformly and without causing glare; they are predominantly designed for tungsten halogen lamps, fluorescent lamps or high-pressure discharge lamps.

  • Ceramic discharge tube
    Discharge tube of a high-pressure discharge lamp. Ceramic discharge tube technology offers better colour stability and higher luminous efficacy than quartz technology.

  • Colour adaptation
    The ability of the eye to adapt to the light colour in the surroundings. Results in the perception of relatively natural colour under different colours of light.

  • Colour compensation
    Procedure in lighting engineering for correcting the light colours from several luminaires with RGB colour mixing in order to ensure that lighting tasks have a uniform colour impression.

  • Colour filter

  • Colour mixing
    In lighting engineering, additive colour mixing using red, green and blue can be used to obtain mixed colours. The combination of all three primary colours produces white light. Subtractive colour mixing starts with the primary colours of cyan, yellow and magenta and filters out particular spectral components.

  • Colour rendition
    Quality of colours as they occur under a given light source. The degree of colour deviation from a reference light source is given by the colour rendition index Ra.

  • Colour rendition index
    The degree of colour distortion under a given light source in comparison with a reference light source. The optimum colour rendition index is Ra = 100.

  • Colour saturation
    Measure for the intensity of a colour between the pure colour and the white point in the chromaticity diagram. Together with hue and brightness, this is one of the three fundamental properties of a colour. Colour saturation is usually given as a percentage.

  • Colour temperature
    Describes the colour of light of a light source. With thermal radiators, this is virtually the same as the actual temperature of the lamp filament in degrees Kelvin (K). For discharge lamps, the colour temperature that is most similar is given. This is the temperature at which a thermal radiator emits light of a comparable colour.

  • Compact fluorescent lamps
    These are fluorescent lamps with particularly compact dimensions achieved by bending or twisting the discharge tube and/or by combining several short discharge tubes. Compact fluorescent lamps have only one lamp cap.

  • Compact projector
    Spotlight with optical systems for the projection of gobos and text templates (patterned filters) for use with various lamp types. Depending on the optical system, a distinction is drawn between a condenser projector and an ellipsoid projector.

  • Condenser projector
    Compact projector

  • Cone vision
    Photopic vision

  • Cones

  • Connected load
    The connected load is the total sum of the nominal wattages of electric loads.

  • Connected power of illumination
    The maximum power of the entire lighting installation, regardless of the actual energy consumption.

  • Constancy
    The ability of visual perception to discern features of objects (size, shape, reflectance, colour) despite changes in the environment (distance, position, lighting). Constancy is absolutely vital in order to create a structured image of reality out of the ever-changing patterns of luminance on the retina.

  • Contrast
    The difference in the luminance or colour of two objects or of one object and its surroundings. The visual task becomes increasingly difficult as the contrast decreases.

  • Contrast rendition
    Criterion for limiting reflected glare. The contrast rendition is expressed by the contrast rendition factor (CRF). It is defined as the ratio between the luminance contrast of a visual task under the given lighting and the luminance contrast under the reference lighting.

  • Control gear
    These devices are necessary for the operation of certain light sources. They primarily refer to current-limiting control gear (chokes) and starters, i.e. ignitors, required to operate discharge lamps but also to transformers required to operate low-voltage halogen lamps. Inductive control gear devices are available either in conventional (CCG) or low-loss versions (LCG). They sometimes require an additional ignitor or starter. Electronic control gear (ECG) work without any additional ignitor and prevent annoying transformer hum or stroboscopic effects.

  • Control gear
    These devices are necessary for the operation of discharge lamps. They primarily refer to current-limiting control gear (chokes) and starters, i.e. ignitors required to operate discharge lamps but also to transformers required to operate low-voltage halogen lamps. Inductive control gear devices are available either in conventional (CCG) or low-loss versions (LCG). They sometimes require an additional ignitor or starter. Electronic control gear (ECG) work without any additional ignitor and prevent annoying transformer hum or stroboscopic effects.

  • Coolbeam
    Coolbeam reflector

  • Coolbeam reflector
    Dichroic reflector which predominantly reflects visible light, but transmits (glass reflectors) or absorbs (metal reflectors) infrared radiation. Coolbeam reflectors result in a lower thermal load on the illuminated objects. Coolbeam reflectors are also known as multimirror reflectors.

  • Cover glass
    The protective layer of a luminaire through which the light is emitted. Depending on the lighting technology, a luminaire can have one or more such layers. The apparent luminance of the cover glass is used when evaluating the glare of a luminaire.

  • Cut-off angle
    Angle above which no direct reflection of the lamp is visible within the reflector. With Darklight reflectors the luminaire cut-off angle is identical to the lamp cut-off angle.

  • DALI
    Abbreviation for Digital Addressable Lighting Interface

  • Dark Sky
    Term used in lighting design for lighting which avoids light pollution in the outdoor area in order to prevent brightening the night sky.

  • Dark Sky technique
    Reflector technology which results in no light being emitted above the luminaire in order to avoid light pollution.

  • Darklight technique
    Reflector technology which results in the observer not being subjected to glare as long as the lamp remains above the cut-off angle. The lamp cut-off angle and the reflector´s luminaire cut-off angle are identical. Darklight technology offers optimum efficiency for maximum visual comfort.

  • Daylight
    Daylight includes the directed, direct sunlight, the ambient light of the sky and the diffuse light from the clouds. The illuminances of daylight are far higher than the illuminances of artificial lighting.

  • Daylight factor
    Ratio between the illuminance produced by daylight on the working plane of a room and the exterior illuminance; the daylight factor can be measured in the daylight simulator.

  • Daylight simulator
    Technical equipment used to simulate sunlight and daylight. Daylight can either be simulated by the hemispherical arrangement of numerous luminaires or by the multiple reflection of a luminous ceiling in a room fitted with mirrors. Sunlight is simulated by a parabolic mirror whose movement can reproduce the sun´s path during the day or the year for any latitude. A daylight simulator allows the relationship between light and shadow in proposed buildings to be simulated on a model, including testing the various lighting control elements and measuring the daylight factors on the model.

  • Daylight systems
    Technical measures based on reflection and refraction in the area of windows and skylights which are used to improve the provision of daylight in a room and, in this way, to reduce the electrical power consumption.

  • Daylight white, tw
    Colour of light

  • Daytime vision
    Photopic vision

  • Dichroic reflector
    Coolbeam reflector

  • Diffuse light
    Diffuse light is emitted from large, luminous surfaces. It produces a soft, uniform lighting with low modelling and brilliance.

  • Diffuser
    Optical element for dispersing the rays of light in order to give a soft light beam. Fitted to the luminaire, the diffuser reduces the lamp luminance and can reduce glare.

  • Digital Addressable Lighting Interface
    Digital control protocol for lighting control within architecture. The system enables luminaires to be individually controlled and can be integrated into building control systems as a subordinate, stand-alone system.

  • Dimmer
    Control device to infinitely vary the luminous flux of a lamp using leading-edge phase control. Can be used with incandescent lamps, low-voltage halogen lamps and fluorescent lamps. Although, it is technically possible to dim high-pressure discharge lamps, it is neither complete nor common.

  • Direct illuminance
    The lighting emitted directly from luminaires onto the working plane, e.g. by downlights.

  • Directed light
    Directed light is emitted from point light sources. One specific direction of light predominates and this provides good effects in terms of modelling and brilliance. Even unmodified beams from open, point light sources produce directed light, in which case, however, since the main direction of the beam is spread with varying intensity in all directions, the common practice is to focus the light into a uniformly directed beam using light guidance.

  • Directional luminaire
    Usually a recessed luminaire which has a beam angle within a defined angular range (rotation and tilt) that can be freely selected. Suitable for retail and exhibition areas.

  • Directive luminaires
    Their design invariably complies with standardised directive luminaires and safety signs; the inscriptions and signs are backlit.

  • Discharge lamps
    Lamp in which the light is produced by electrical discharge through gases or metal vapours. A distinction is drawn between low-pressure and high-pressure discharge lamps. Low-pressure discharge lamps include conventional fluorescent lamps and compact fluorescent lamps. Their light is produced by exciting the fluorescent substances with radiation. High-pressure discharge lamps include mercury vapour lamps, Halogen-metal halide lamps and high-pressure sodium vapour lamps. Their light spectrum is due to their unique composition and high operating pressure.

  • DMX
    Abbreviation for Digital Multiplexed. The digital control protocol is most often used for lighting control with theatrical stage lighting.

  • Dominant wavelength
    Measurement parameter for identifying a mixture of colours by one wavelength. In the chromaticity diagram, the dominant wavelength can be calculated by extrapolating a line from the white point through the given colour locus to meet the spectral colour line. The opposite is the complementary wavelength. The dominant wavelength has various uses including colour classification of LEDs.

  • Double washlights
    A luminaire used in corridors and hallways to provide uniform illumination of the parallel walls and the floor area.

  • Double-focus downlight
    Downlight with elliptical reflector system and Darklight reflector. It provides maximum luminous flux from the smallest ceiling aperture.

  • Double-focus wallwasher
    A luminaire used to provide uniform illumination of walls. The optical system focuses the light into a second focal point and only emits reflected light. This allows the lamp to be completely shielded for improved visual comfort.

  • Downlight
    A compact luminaire with a round or square opening. Downlights are designed for mounting in or on ceilings or for suspended mounting. Their light is predominantly, but not exclusively, directed downwards onto horizontal surfaces.

  • Electronic control gear
    Control gear

  • Ellipsoid projector
    Compact projector

  • Elliptical reflector

  • Emergency lighting
    Term used to describe the lighting of emergency exits and escape routes using emergency lighting luminaires and also to describe the identification of emergency exits using illuminated safety signs or directive luminaires.

  • Emission angle
    The angle between the points of a light intensity distribution curve at which the light intensity drops to 50% of the value measured in the main beam direction. The emission angle determines the light beam diameter.

  • Ethernet
    Data network technology for local networks which permits the exchange of data between all devices connected to a local area network (LAN).

  • Eulumdat
    European Lumen Data format that describes the light intensity distribution of luminaires.

  • EVG
    Abbreviation for Electronic Control Gear.

  • Exhibition lighting
    A type of lighting designed to add visual emphasis to exhibits; it can cover a wide area or be accentuated. In the area of museums and galleries, light protection plays an important role.

  • Eye
    The eye is an optical system containing the cornea and a deformable lens, which project the image of the outside world onto the retina, as well as the iris which broadly regulates the amount of the incident light by adjusting the pupil opening. In the retina, the incoming photostimuli are converted into neuron impulses by receptor cells. The eye has two systems of photoreceptors: the rod cells and the cone cells. The rods are distributed relatively uniformly across the retina; they are highly sensitive to light and enable wide-angle vision under low illuminances (scotopic vision). Their visual acuity is low, however, and colours are not perceived. The cones, on the other hand, are predominantly concentrated in the fovea, a small depression in the retina located on the optical axis or visual axis. The cones enable sharp, coloured vision within a limited angle of vision, but require high illuminances (photopic vision).

  • Facetted reflector
    Reflector with flat facets which produces a more cohesive beam than conventional, mirror-finish reflectors.

  • Fading
    Transition between light scenes. Fading in refers to the starting-up of a light scene, while fading out refers to the ending of a light scene.

  • Fading time
    The duration of the light scene transition is known as the fading time.

  • Fibre optics
    Optical instrument used to guide light along any route, even around curved paths. The light is channelled along the light guide system, a solid rod or tubular conductor made of transparent material (glass or synthetic fibres, tubes or rods), which function through total internal reflection.

  • Fill light
    Type of lighting which discreetly brightens an object, a setting or a shadow using a soft light without the observer being consciously aware of it. The fill light complements the key light.

  • Filter
    Optical elements with selective transmission. Filters only transmit part of the incident radiation, to produce either coloured light or by filtering out invisible radiation such as ultraviolet or infrared. Filter effects can be achieved by absorption (absorption filter) or reflection (reflection filter). Interference filters are effective reflection filters that work using special vaporised coatings; they are also known as dichroic filters.

  • Flood
    Common term for wide-beam reflectors or reflector lamps.

  • Floodlight
    Luminaire with a wide beam angle that can be directed at any point by rotating and tilting; used mainly with track.

  • Floor washlights
    Luminaire type which is fitted either individually or in rows at low level in or on the wall. These luminaires illuminate the floor area uniformly and without creating glare.

  • Fluorescence
    Fluorescence is a process in which substances are excited by means of radiation to produce light; the wavelength of the emitted light is always higher than the wavelength of the incident radiation. One of the primary technical applications of fluorescence is in fluorescent lamps where ultraviolet radiation is converted into visible light.

  • Fluorescent lamp
    A tubular low-pressure discharge lamp containing mercury vapour. The ultraviolet radiation produced by the mercury discharge is converted into visible light by fluorescent substances on the internal surface of the tube. Different colours of light and colour rendition qualities can be obtained by combining different fluorescent substances. The fluorescent lamp usually has heated electrodes enabling it to be started with relatively low voltages. Fluorescent lamps require conventional or electronic control gear.

  • Focal glow
    Focal glow creates accents. Light is actively involved in conveying information by visually emphasising areas of significance and diminishing the less important areas.

  • Fovea

  • Fresnel lens
    Stepped lens where the lens effect is achieved by the concentric arrangement of lens segments. Fresnel lenses are used for stage spotlights and spotlights with adjustable beam angle.

  • Gateway
    A data exchange protocol that enables communication of different protocols in a network.

  • General lighting
    Uniform lighting of an entire space without giving special consideration to individual visual tasks.

  • General service lamp
    Incandescent lamp

  • Glare
    Collective term for the reduction of visual performance or the impairment of perception due to high luminances or luminance contrasts in the visual surroundings. A distinction is made between discomfort glare and disability glare: the former concerns an objective reduction in vision and the latter a subjective impairment due to any disparity between the luminance and information content of the observed area. The glare can be caused by the lamp itself (direct glare) or by reflection of the lamp (reflected glare).

  • Global illumination
    In three-dimensional computer graphics, a calculation used to describe the simulation of all ways in which light rays may radiate.

  • Global radiation
    The sum of solar radiation and surrounding sky radiation.

  • Gobo
    Common term in spotlight illumination (originally from stage lighting) for a mask or image template (patterned filter) used to create effects and project images using a projecting optical system.

  • Grazing light
    Type of lighting where the light is incident to the surface at a very shallow angle. Used to emphasise surface structure and texture.

  • HDR
    Abbreviation for High Dynamic Range

  • High Dynamic Range
    Describes a very high contrast relationship in a digital image. Images in HDR format can store a higher luminance contrast than Low Dynamic Range with 255 gradations.

  • High-pressure discharge lamps
    This category includes mercury vapour lamps, metal halide lamps and high-pressure sodium vapour lamps.

  • High-pressure sodium vapour lamp
    High-pressure discharge lamps containing sodium vapour. Because the sodium vapour is aggressive at high pressures and would destroy glass, the inner discharge tube consists of aluminium-oxide ceramic, enclosed in the external glass envelope. The colour of light produced is in the warm white range. High-pressure sodium vapour lamps require ignitors and control gear.

  • Honeycomb anti-dazzle screen
    Anti-dazzle attachment with honeycomb structure used to restrict the light beam and reduce glare.

  • Hotel lighting
    Hotels are public areas with particularly stringent demands on the quality of the lighting design. Hotel lighting includes architecturally-oriented lighting in entrance areas, atmospheric mood lighting in the restaurant areas, multifunctional lighting in conference centres, economical lighting in the thoroughfares and corridors, and private lighting atmospheres in the hotel rooms.

  • Hub
    Node for connecting network segments or hubs, for example via Ethernet.

  • IES
    International data format for describing the light intensity distribution of luminaires.

  • Ignitor
    A component in control gear that facilitates the ignition of discharge lamps by producing voltage peaks.

  • Illuminance
    The illuminance, measured in the units of lux (lx), is the ratio between the luminous flux incident upon an area and the size of that area.

  • Incandescent lamp
    Thermal radiator where light is created by heating a Tungsten filament. The incandescent filament is enclosed in a glass bulb filled with an inert gas such as nitrogen which prevents it from oxidising and delays the vaporisation of the filament material. Incandescent lamps are available in numerous forms, the main groups being general service lamps with pear-shaped, clear or frosted bulbs, reflector lamps with a variety of internal reflective coatings and PAR lamps made of moulded glass with integral parabolic reflector.

  • Indirect lighting
    Lighting which is emitted from the luminaires and indirectly reflected onto the working plane via reflective surfaces, e.g. uplights.

  • Infrared radiation
    Invisible thermal radiation in the wavelength range > 780 nm. Infrared radiation is produced by all light sources, but especially by thermal radiators, where it constitutes the majority of the emitted radiation.

  • Interference
    Physical phenomenon produced when waves that are out of phase are superimposed; it can result in selective weakening of the intensity of various wavelengths. Interference is used in filters and reflectors for selective transmission or reflection, respectively.

  • Interference filter

  • Intersecting beam
    Hyperbolic shape due to the intersection of the light beam and the wall; produced, for example, by downlights.

  • Inverse square law
    Lambert´s Cosine Law

  • Inverse square law
    Law which states that the illuminance is a function of the distance from the light source. The illuminance is inversely proportional to the square of the distance.

  • Inverse square law
    Lambert´s Cosine Law

  • IP rating (Protection class)
    Indicates the measures taken to prevent contactable metal parts from conducting current in case of a fault occurring.

  • Isoluminance contour diagram
    Diagram representing luminance distributions, where a single reference plane is shown with contours superimposed of the same luminance.

  • Isolux diagram
    Diagram representing illuminance distributions, where a single reference plane is shown with contours superimposed.

  • Key light
    Type of lighting using accent light to considerably improve the appearance of an object or setting. To avoid harsh contrast, a fill light is used.

  • KNX
    Abbreviation for Konnex. Standardised digital system for building control, e.g. for lighting, heating and ventilation.

  • Lamp
    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.

  • Lamp cap
    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.

  • Lamp life
    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.

  • Lampholder
    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.

  • LAN
    Abbreviation for Local Area Network. A permanently installed local computer network over short distances.

  • LCG
    Abbreviation for Low-loss Control Gear.

  • LDS
    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.

  • LED
    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.

  • Lens
    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.

  • Lens wallwasher
    Luminaires with asymmetric light intensity distribution for uniform wall lighting. The light is spread by a lens.

  • Life
    Lamp life

  • Light beam
    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.

  • Light colour
    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.

  • Light fastness
    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.

  • Light pollution
    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.

  • Light protection
    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.

  • Light scene
    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.

  • Light sequence
    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.

  • Light source

  • Light structure
    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.

  • LON
    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.

  • Lumen, lm
    Unit of luminous flux

  • Luminaire
    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.

  • Luminaire classification
    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.

  • Luminance
    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.

  • Luminescence
    Collective term for all forms of light not created by thermal radiators (photo-, chemo-, bio-, electro-, cathodo-, thermo- or triboluminescence).

  • Luminescence conversion
    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.

  • Luminous efficacy
    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.

  • Luminous flux
    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.

  • Luminous intensity
    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.

  • Luminous power
    Another term for luminous flux; in radiation physics, it is equivalent to the radiant power.

  • Lux, lx
    Unit of illuminance

  • Mains voltage
    The electrical voltage supplied through mains power distribution. In most regions of the world the mains voltage is 230 V at 50 Hz. Other supply voltages may require transformation equipment.

  • Maintenance
    Term for the measures taken for the ongoing and effective operation of a lighting installation. It includes replacing lamps, cleaning luminaires and setting the direction of any spotlights. Maintenance is taken into consideration in the design of a lighting system using the parameter light loss factor.

  • Maintenance factor
    Light loss factor

  • Mercury vapour lamp
    High-pressure discharge lamp containing mercury vapour. In contrast to low-pressure discharge which creates ultraviolet light almost exclusively, mercury vapour emits visible light under high pressure, but with a low red content. The red content can be supplemented and the colour rendition improved by adding other fluorescent substances.

  • Mesopic vision
    Intermediate state between photopic (day) vision using the cone cells and scotopic (night) vision using the rod cells. The levels of colour perception and visual acuity take on corresponding intermediate values. Mesopic vision covers the luminance range from 3 cd/m2 to 0.01 cd/m2.

  • Metal halide lamp
    High-pressure discharge lamp filled with metal halides. The large number of raw materials available allows metallic vapour mixtures to be created whose discharge generates high luminous efficacy and good colour rendition.

  • Modelling
    The accent lighting of three-dimensional shapes and surface textures using directed light from a point light source. It is generally expressed through the improvement in shadow quality.

  • Multi-mirror
    Coolbeam reflector

  • Multifunctional lighting
    This is a typical lighting requirement in hotels and congress halls hosting seminars, conferences, receptions and entertainment. The multifunctional lighting may be created by using several lighting components which are switched on separately and additively, often linked to programmable lighting controls.

  • Museum lighting
    A particular branch of exhibition lighting; it places special demands on the design of the lighting and on the light distribution on the exhibits and architecture and also requires light protection for sensitive exhibits.

  • Office lighting
    This is specifically oriented about the requirements for VDU workplaces; see VDU lighting. A distinction is drawn between ambient lighting, workplace-oriented ambient lighting and individual workplace lighting.

  • Optical Cut-off
    Analogous to the cut-off angle, the optical cut-off indicates the angle outside of which there is no glare. Whereas darklight reflectors have a screening effect, the angle here is achieved only through light guidance by means of the lens.

  • PAR lamp
    Incandescent lamp

  • Parabolic reflector

  • Perception psychology
    A branch of the sciences concerned with various aspects of perception, in particular neural response and processing of sensory stimuli.

  • Permanent Supplementary Artificial Lighting (PSALI)
    Additional artificial lighting especially in rooms lit only by windows on one side. PSALI compensates for the fall in illuminance as the distance from the window increases.

  • Photometer
    Instrument used to measure photometric performance. The primary dimension is illuminance, other dimensions are derived from the illuminance. Photometers are adjusted to the spectral sensitivity of the eye. Special measuring equipment called goniophotometers are required for measuring the light intensity distribution of luminaires.

  • Photon mapping
    Algorithm used in light simulation which is primarily employed as an extension of ray tracing based processes.

  • Photopic vision
    Also: day vision. Vision involving adaptation to luminances of above 3 cd/m2. Photopic vision is performed by the cone cells and is therefore concentrated on the area of the fovea. The visual acuity is high and colours are perceptible.

  • Planckian radiator
    Black-body radiator. Ideal thermal radiator whose radiation properties are described by Planck´s Law.

  • Play of brilliants
    Play of brilliants is a decorative lighting component. The brilliant effects can be from lamps or illuminated materials - from a candle flame and chandeliers to sculptures of light, they contribute to the atmosphere of prestigious and emotive settings.

  • Point illuminance
    In contrast to the average illuminance, the point illuminance expresses the illuminance at a defined point in space.

  • Point light source
    Term describing compact, virtually point-form sources. The light from point light sources can be optimally directed and focused. Conversely, linear or area light sources produce diffuse light, which becomes more diffuse the more the light disperses.

  • Projection
    Optical image produced by a two-dimensional mask or a gobo on a surface. Luminaires for projection require an optical imaging system. The focus can be adjusted using a lens system.

  • Protection mode
    This indicates the protection classification of a luminaire. The combination of two digits indicates the degree to which the luminaire is protected against the ingress of foreign bodies and water.

  • Radiant flux
    This refers to the radiant power per square metre of area; the maximum value for daylight is approximately 1 kW/m2.

  • Radiant power
    From electrical lamps, this is the product of converted electrical energy. Physical unit: watt. In the wavelength range between 380 nm and 780 nm, the radiant power (W) is quantified as the light output (lm).

  • Radiosity
    Light simulation calculation method. With the radiosity method, light rays are emitted from the light source and reflected when they strike a surface.

  • Ray tracing
    Light simulation calculation method. The ray tracing method is based on rays of light that are emitted from an imaginary eye to the model and the light sources.

  • Re-ignition
    The restarting after switching off or after a power failure. Many discharge lamps can only be re-ignited after a cooling down period. In these cases, instant re-ignition is only possible with the aid of special high-voltage igniters.

  • Recessed ceiling luminaires

  • Recessed floor luminaire
    A luminaire which is flush-mounted in the floor or ground and has a high protection mode. These luminaires are used to mark out routes and pathways and also to dramatically illuminate objects and architectural details.

  • Reflection
    The ability of surfaces to reflect light. The percentage reflection is known as the reflectance, defined as the ratio of reflected to incident luminous flux. Reflection can be directed or diffuse.

  • Reflector
    Light-directing system based on reflecting surfaces. The main characteristics of a reflector are its reflectance and spread. For concave and convex mirror reflectors, a further characteristic is the curvature of its cross section, i.e. the reflector contour. Parabolic reflectors align the light from a light source located at the focal point into a parallel beam, spherical reflectors reflect it back to the focal point and elliptical reflectors focus it to a second focal point.

  • Reflector lamp
    Luminaires with integral reflector. The reflector lamps are available with different beam angles. A special form is the coolbeam reflector.

  • Refraction
    Phenomenon through which the direction of light is changed as it passes through mediums of differing densities. The refractive power is given by the refractive index.

  • Refraction

  • Refraction

  • Relay
    A switch which is actuated by current. A relay is usually activated via a separated circuit and can open or close one or more circuits.

  • Restaurant lighting
    Characteristic: low ambient lighting, focal light on the table with accentuation of specific areas of the room and decor. Use of lighting controls to adjust the lighting to suit the different requirements during daytime and nightime.

  • RGB
    Abbreviation for Red Green Blue. The RGB colour mixing used in lighting technology is based on additive colour synthesis to produce light of different colours.

  • Room surface maintenance factor
    Calculation value for the maintenance plan of a lighting system which considers the drop in luminous flux due to dirty walls.

  • Scallop
    Beam scallop

  • Scenography
    The term for scenic effects. In lighting, scenography refers to the transformation of a room or area using light with the inclusion of the dimension of time.

  • Scotopic vision
    Also: night vision. Vision involving adaptation to luminances of below 0.01 cd/m2. Scotopic vision occurs through the rod cells which are mainly in the periphery of the retina. The visual acuity is low and colours cannot be perceived, but there is high sensitivity to the movement of observed objects.

  • Scotopic vision
    Scotopic vision

  • Sculpture lens
    Lens with a parallel ribbed texture that spreads the light beam in one axis, leaving it largely unchanged in the other axis. In museum lighting, the sculpture lens is used to uniformly illuminate tall or long sculptures with an oval beam.

  • Sensor
    Device for measuring environmental conditions and events within the surroundings. The sensor measures the value and sends a signal when the limit has been exceeded in order to trigger an action such as adjusting the lighting.

  • Shielding angle
    With downlights, this is the angle subtended between the horizontal plane and a straight line extended from the edge of the luminaire to the edge of lamp. It is a dimension for the visual comfort of a luminaire in addition to the luminaire cut-off angle.

  • Shop window lighting
    In essence, shop window lighting design is closely linked to showroom lighting; it primarily involves the use of accent lighting, often with theatrical scenic effects using coloured light, lighting projections and dynamic lighting control.

  • Showroom lighting
    This describes lighting which is designed based on the components of horizontal and vertical ambient lighting together with accent lighting; multi-component lighting typically with discharge lamps (ambient lighting) and tungsten halogen lamps (accent lighting). Such retail lighting can often be used to convey a company´s corporate identity.

  • Solar architecture
    Architecture designed to allow solar energy and daylight to be utilised as energy and light, respectively.

  • Solar protection
    Technical measures which use absorption, reflection and refraction to control direct sunlight in order to improve the visual comfort (glare protection) and reduce the thermal load in the room.

  • Spectrum
    Distribution of radiation intensity of a light source over a specific range of wavelengths. Both colour of light and colour rendition are a result of the spectrum. The basic types of spectrum are distinguished depending on how the light is produced: the continuous spectrum (daylight and thermal radiators), the linear spectrum (low-pressure discharge) and band spectrum (high-pressure discharge).

  • Spherolit reflector
    Light-directing system based on reflective surfaces with spherical segments. The light intensity distribution is determined by the reflectance, the reflector contour, the number of spherical segments and the segment radii.

  • Spill light
    Unwanted light emitted outside the main beam. Spill light can cause glare, and outdoors, for example, it is often a source of light pollution.

  • Spot
    Common term for narrow-beam reflectors or reflector lamps.

  • Spotlight
    Luminaire in which the predominant direction of light distribution can be aimed at any desired point by rotating and tilting; used mainly with track.

  • Starter
    Ignitor for fluorescent lamps.

  • Stroboscope effect
    This is a flickering effect which results in the apparent change in the speed of moving objects. This can even go so far as to make objects appear to be stationary or move in the opposite direction. It is caused by light pulsating at or close to mains frequency. Stroboscopic effects can occur when lighting is provided by discharge lamps. It can be remedied by phase-shifted operation (lead-lag circuit, connecting to a three-phase power network) or by high-frequency electronic control gear.

  • Sun simulator
    Daylight simulator

  • Sunlight

  • Task lighting
    In general, this refers to the lighting of workplaces; specifically, it refers to the additional lighting of workplaces which is designed to suit the actual visual task and is additional to the ambient lighting.

  • Task lights
    These luminaires are predominantly equipped with energy-saving, compact fluorescent lamps or tungsten halogen lamps and have freely adjustable light heads and good glare control; they are suitable for use in a wide variety of workplaces.

  • Thermal radiator
    A radiation source from which light is emitted by heating a material, generally tungsten, as the filament material in an incandescent lamp.

  • Thermoluminescence

  • THI Daylight elements
    THI is the term for Transparent Heat Insulation. THI daylight elements are plastic screens fitted between clear glass panes with high light transmittance and low diathermic characteristics; they are suitable for providing interior rooms with daylight.

  • Track
    The basis for a variable lighting solution designed to meet a range of specific requirements. Track can be fitted with additional luminaires at any time to adjust for changes in room usage. Typically used with spotlights and floodlights, especially in presentations and exhibitions.

  • Trailing edge technology
    Method of dimming in which the power consumption of the lamps is limited by the trailing edge of the alternating current wave. With trailing edge technology, the current is switched on immediately after the alternating voltage passes through the zero point and is switched off before the next zero crossing. Trailing edge technology is used for controlling electronic control gear.

  • Transadapter
    A device used to connect a luminaire, especially a spotlight or floodlight, both mechanically and electrically to a track; used together with an integrated electronic transformer or an electronic control gear.

  • Transformer
    Required to operate low-voltage halogen lamps; a distinction is drawn between conventional and electronic transformers.

  • Transmission
    The ability of materials to transmit light. The dimension of transmission is transmittance, defined as ratio of transmitted luminous flux to incident luminous flux. Transmission can be directed or diffuse.

  • Tungsten halogen lamp
    Compact incandescent lamp filled with halogen to prevent the deposit of vaporised filament material onto the inner glass wall. Tungsten halogen lamps have a higher luminous efficacy and longer functional life than general service lamps.

  • Twilight vision
    Mesopic vision

  • UGR
    Unified Glare Rating; method for assessing psychological glare, especially at the workplace.

  • Ultraviolet radiation
    Invisible radiation beyond short-wave light (wavelength < 380 nm). Light sources used in architecture usually only emit a limited amount of ultraviolet radiation. Ultraviolet radiation can have detrimental effects, particularly causing colours to fade and materials to become brittle. Ultraviolet filters absorb this radiation.

  • Uplight
    Pendant luminaires, wall luminaires, floor luminaires or free-standing luminaires that emit their light upwards.

  • Utilisation factor
    This factor describes the influence of spatial geometry and the reflectance of its peripheral surfaces on the residual luminous flux arriving on the defined working plane.

  • Utilisation factor method
    Method for calculating the average illuminance in a room using the light output ratio, the utilisation factor and the luminous flux of the lamp.

  • Varychrome
    Attribute describing luminaires that can generate light of any colour, for example, using RGB colour mixing.

  • VDU lighting
    Lighting in administrative buildings which is heavily regulated by guidelines and regulations. It is characterised by requirements for the illuminance level, light distribution and glare limitation, specifically for preventing reflections on monitor screens, worktops and keyboards.

  • Visual acuity
    This term is used to describe the ability of the eye to perceive detail. It is measured in Visus, defined as the inverse value of the size of the smallest perceptible detail of a specified visual task in minutes of a degree.

  • Visual angle
    The subtended angle within which an object is perceived; the measurement of the size of the image of an object on the retina.

  • Visual comfort
    Visual comfort expresses the lighting quality with regard to parameters such as illuminance, elimination of glare and colour rendition.

  • Visual performance
    This term is used to describe the ability of the eye to perceive or the visual properties of the object to be viewed. The difficulty of a visual task increases as the colour contrast or luminance contrast decreases, and also as the size of detail decreases.

  • Voltage
    Physical dimension. Causes charge carriers to be set in motion and electrical current to flow in an electrical conductor.

  • Wallwasher
    Luminaire with special reflector system or reflector lens system for uniform lighting of walls; it is essential that the wallwashers are spaced equally and are parallel to the wall.

  • Warm white, ww
    Colour of light

  • Washlights
    Luminaire with a combination of darklight reflector and ellipsoid reflector which achieves a high level of visual comfort combined with even wall lighting; the prerequisite for this is the regular arrangement of wallwashers parallel to the wall.

  • Watt
    Physical unit of power. It is the product of voltage and current.

  • Wide flood
    Common term for very wide-beam reflectors or reflector lamps.

  • Workplace lighting
    In contrast to ambient lighting, this lighting is designed for one specific workplace, e.g. using task lights.


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