# lighting

Lighting in a train station
Exterior lighting of the Cologne Cathedral

The term lighting refers to the generation of light with the help of an artificial light source (lighting system) and the subsequent visualization of objects that do not shine themselves. This artificial light makes people independent of natural light sources (primarily the sun ) and serves to improve visual performance (visual effect). It can influence the circadian rhythm (biological effect) and increase well-being (emotional effect).

The early historical use of open fire is the first and at the same time the simplest form of lighting. In the further course of human history , especially from the 18th century, additional possibilities were developed through electrical lighting, combined with the development of new techniques and materials. The aim is to optimize the lighting in terms of energy consumption , efficiency and service life and to improve the quality of light.

In lighting technology, a basic distinction is made between indoor and outdoor lighting. The interior lighting includes living rooms as well as workplaces of all kinds as well as public spaces such as restaurants or theaters. Outdoor lighting essentially includes street lighting , the lighting of buildings (see lighting (architecture) ) and that of sports facilities . Various standards, most of which are harmonized at European level, regulate the individual areas of application and define quantitative and qualitative requirements for lighting systems.

## history

The discovery and utilization of fire in the early days around 300,000 years ago marked the beginning of lighting. In addition to warmth, the open fire also provided sufficient light to illuminate dwellings and caves. Over time, other means of lighting developed from this, such as the pine chip , the wax candle and the oil lamp . The discovery of the gas lamp in 1783 by the Dutchman Johannes Petrus Minckeleers brought decisive progress in lighting technology . With the advent of electricity in the mid-19th century, attempts were made to use electricity for lighting ( electric arc lamps ). Thomas Alva Edison finally applied for a patent for the incandescent lamp in 1879, thus laying the foundation for the use of modern lighting.

## Components of the lighting

Electric lighting devices basically consist of a light source (technically a lamp ) and a lamp . The lamp is used to accommodate one or more light sources and to connect them to the power source. The luminaire also directs and distributes the light generated by the light source. In everyday life, the lamp is often called a lamp. The following light sources are used today in lighting technology (selection):

Lightbulb
A gas-filled glass bulb with internal filament of tungsten . Electric current heats the filament so that not only heat but also light is emitted. Because of its low efficiency - namely a fraction of the light yield of other processes - the incandescent lamp has not been allowed to be placed on the EU-wide market since 2012.
Halogen light bulb
Halogen lamps represent a further development of the incandescent lamp. The glass bulb is filled with a halogen , which improves the service life and efficiency of the lamp.
Fluorescent lamp
Fluorescent lamps come as long, cylindrical glass tubes, straight or curved. They are coated on the inside with fluorescent powder that converts UV light through fluorescence . The gas discharge takes place in the low-pressure filling, which also contains some mercury vapor and is operated on an electronic ballast (EVG) that replaces the old starter plus magnetic choke. Small, namely folded or coiled lamps for screwing in or plugging in are called compact fluorescent lamps, and more generally energy-saving lamps.
Mercury vapor lamp
The bulb of mercury vapor lamps is coated on the inside with fluorescent material, it absorbs UV radiation. The lamps are started and controlled by a ballast. Because of the mercury content and low light output, they have been subject to a production and sales ban in the EU since 2015. The high pressure variant was mainly used in street and industrial lighting.
Metal halide lamp
These lamps are a further development of the mercury vapor lamp based on other low-boiling metals, with the addition of halogens increasing the light output. They are operated with a ballast and have good color rendering and very good light control properties.
Sodium vapor lamp
Sodium vapor lamps work with glass bulbs or glass tubes with ceramic burners and are operated with a ballast. They are available as low or high pressure types. They have a very high luminous efficacy, but low color rendering. Low-pressure lamps are distinctly monochrome yellow (after a neon-pink ignition phase). Their light penetrates haze and fog well, which is why these light sources are used to illuminate harbors, tunnels and pedestrian crossings as well as for property protection.
Light source with light emitting diodes
This is a lamp that consists of light emitting diodes (English LED) in different arrangements. The best service life and light yield (efficiency) are the advantages. As a semiconductor, the light-emitting diode itself is destroyed by overheating, which is why it is only built up to certain electrical outputs, is coupled to cooling surfaces and must not be operated next to a hot light bulb.
Light-emitting diodes (English LED) are semiconductor crystals that are electrically excited to glow. The proportion of thermal energy emitted by electroluminescence is 50 to 70 percent, so this heat must be effectively dissipated through thermal management in order to maintain the service life. The advantages of LEDs are long service life and light output (efficiency); LEDs with more than 200 lm / W are already being used. Retrofits, i.e. lamps in the classic lamp shape with screw or plug-in bases, achieve 78 to 117 lm / W due to their design which is not optimal for heat dissipation, LED filament lamps only achieve a little more (up to 126 lm / W). A switch-on delay of typically 1/10 s when the electronics start up is characteristic.
LED modules
Modules usually consist of several LEDs, attached to a carrier and optics with lenses and reflectors. As a rule, they are permanently installed in luminaires or they are replaced by specialist staff.

There are also glow lamps (iron operating display , voltage tester), xenon photo flash and stroboscope tubes and electroluminescence.

## application areas

### Outdoor lighting

Street lights in the city center

Lighting systems that are operated outdoors or outdoors are part of outdoor lighting. Compared to interior lighting, exterior lighting requires a higher degree of protection for the luminaires, as it has to be better protected against contact and the ingress of foreign bodies and moisture. The areas of application include streets, paths and squares as well as parks and gardens. Outdoor lighting is also used to illuminate sports facilities, tunnels and underpasses and to illuminate facades and objects outdoors. Another important area are workplaces in the open air, such as container stations, port facilities, construction sites, chemical plants or petrol stations. Outside lighting in particular causes light pollution .

### Interior lighting

Lighting in a meeting room

Lighting systems that are operated inside buildings count as interior lighting. Important areas of application are workplace lighting and living space lighting . For workplaces, depending on the application, certain parameters are defined in standards that must be adhered to when planning the lighting . For example, the illuminance , the luminance distribution or the light color are specified. In this context, it is also important to correctly define the visual task. Errors in the planning of interior lighting systems can impair visual performance and lead to overstrain of the eyes or neck muscles.

### Lighting in the (indoor) workplace

The usual room lighting by lamps, ceiling lights or computer screens does not represent a hazard from optical radiation when used as intended. The room lighting must, however, be sufficient for the visual tasks of the employees. The Code of Practice for workplaces ASR A3.4 and the DIN EN 12464-1 describe visual and photometric requirements for artificial lighting of workplaces in interiors . There you will find information on the necessary illuminance depending on the workplace and specifications for limiting glare .

The normative requirements do not take into account the significantly growing number of older workers, whose eyesight is deteriorating and who are dependent on stronger lighting. By retrofitting daylight sensors, however, the lighting level can be controlled as required. Additional setting options for lights at each workstation also enable individual regulation.

For stage lighting in the theater, opera or concert, high-power spotlights are used to illuminate a scene or people ("spotlight"). In addition to the strong glare effect of these lighting elements , which often makes looking inside impossible, the exposure limit values for blue light hazard ( photoretinitis ) can also be exceeded. This topic is also a current research subject.

Light-emitting diodes also require attention in occupational safety. LED and OLED differ in their technical structure (with and without optics, as a single source or array). It is therefore difficult to study their radiation parameters. The previously in industrial safety used standards in this case can sometimes no longer be applied, so that the development of new assessment and measurement rules is necessary.

## Independent areas of application

### Illumination at events

Lighting a stage

A distinction is made in event lighting (illumination) between theater light , TV light and the show light used at stage events . All three differ greatly in terms of the type of lighting, but there are similarities.

With theater lighting (→ theater lighting ), the lighting is usually presented in scenes, which in turn enjoy a high degree of artistic freedom. Many colors can be used, e.g. For example, a theater actor can sometimes be "illuminated" in yellow or blue. The lighting at the front of a stage is also known as the spotlight .

TV light , on the other hand, is usually white, where colors only appear as effects or accents and are represented by moving heads , for example . Deep, hard shadows are unsuitable because no high contrast or dynamic range can be transmitted. The illumination of television is achieved, for example, with large-area Fresnel lens headlights that evenly illuminate a room or object. The television light illuminance ( lux ) must reach certain values, which should be higher (analog up to 1500 lux) or lower (digital between 400 and 800 lux) depending on the technology of the OB van (digital or analog OB van ). The illumination of television studios can also be combined with diffuse artificial light and daylight .

The show light , in turn, is more similar to theater light , color accents are set, typical devices are blinders , moving heads and PAR spotlights (well-focused spotlights). The illumination is now and then achieved from the edge of the stage with 2–5 kilowatts.

### Vehicle lighting

Bus with vehicle lighting and destination display

→ Main article: Vehicle lighting

Vehicle lighting is a separate, extensive area of ​​application. The lighting equipment of vehicles includes all lights, headlights and reflective equipment (such as reflector and luminous colors ) that have an external effect. Their size and attachment is stipulated by law.

### Lighting in photography

In color photography, light with a particularly good color rendering index must be used. Incandescent lamps with a particularly high filament temperature (photo lamps ) or xenon flash light meet these requirements .

→ Main article: Flash light and flash methods

In order to reduce the red-eye effect in the case of flash from the direction of exposure, the eye must adapt to bright light or a pre-flash (small pupil opening). A fill flash can help illuminate the subject in backlit conditions.

In black and white photography, for example, red filters can also be used to hide imperfections in portraits.

The photographer designs the lighting by means of indirect lighting (diffusing screen or diffusing reflective surfaces) in such a way that, for example, side lighting lets the plasticity emerge while at the same time lightening the shadows. The design of backlighting effects with light sources hidden by the object is also typical. All of these effects and designs are also possible with flash light by installing conventional light sources at the location of the mother and daughter flash light sources in order to simulate the illumination.

With the so-called cross-polarization flash technology , both the flash and the lens of a camera are each covered with a polarizing filter . This means that all direct light reflections can be filtered out and only diffuse light (from the flash) remains. This makes it easier to take pictures of reflective surfaces with a flash.

## Parameters and measurement

In lighting technology, there are various parameters that are used to describe the properties and requirements of lighting. The following table shows a selection of the most important parameters:

size symbol SI unit (character) description
Luminous flux ${\ displaystyle {\ mathit {\ Phi}} _ {\ mathrm {v}}}$ Lumen (lm) Radiated power of a light source, weighted with the sensitivity curve
Amount of light ${\ displaystyle Q _ {\ mathrm {v}}}$ Lumen second (lms) Radiation energy of a light source, weighted with the sensitivity curve
Light intensity ${\ displaystyle I _ {\ mathrm {v}}}$ Candela (cd) Luminous flux per solid angle , measured at a great distance from the light source; indicates how intensely a light source shines in a certain direction. For a spatially isotropic light source, the luminous flux is equal to the luminous intensity multiplied by the full solid angle ${\ displaystyle 4 \ pi}$
Illuminance ${\ displaystyle E _ {\ mathrm {v}}}$ Lux (lx) Luminous flux per illuminated area; indicates how intensively the area is illuminated
Light output ${\ displaystyle \ textstyle \ eta}$ Lumens per watt (lm / W) Quotient of luminous flux and electrical power; indicates the efficiency of a light source
Luminance ${\ displaystyle L _ {\ mathrm {v}}}$ Candela per square meter (cd / m²) Luminous intensity of a light source, based on its projected area (perpendicular to the viewing direction); Humans perceive this quantity as the brightness of a surface emitting light

The measurement of light ( photometry ) generally deals with the amount of usable light on a surface or with the light from a source, together with the colors reproduced from it. The human eye reacts differently to different colors in the visible spectrum, which is why photometric measurements must always include the sensitivity function . The standard unit of measurement ( SI value ) for photometric light intensity calculations is the candela (cd), which describes an intensity. All other parameters in photometry are derived from the candela (e.g. luminance with the unit candela per square meter). The luminous flux that is emitted from a source is specified in lumens .

### Glare

Some measurement methods have been developed to measure the glare of indoor lighting, such as: B. the Unified Glare Rating , the Visual Comfort Probability or the Daylight Glare Index . In addition to these methods, four factors are responsible for an unpleasant perception of lighting: the luminance of the light sources, the solid angle of the exposed surfaces, the background lighting and the position of the light sources in the field of vision. A distinction must be made between direct glare from lights or luminous surfaces and reflected glare from reflections on shiny surfaces.

### Color properties and exposure

In order to define the color properties of a light, the lighting industry mainly uses two parameters: the correlated color temperature (also called Kelvin color temperature, or Correlated Color Temperature - CCT) to describe the “warmth” or “coolness” of a light, and the Color rendering index R a ( Color Rendering Index - CRI), which reflects the ability of a light source to make surfaces look natural. The color temperature is given in Kelvin (K) and is usually described by the industry as warm white (2,700 to 3,300 K), neutral white (above 3,300 to 5,300 K) or daylight white (above 5,300 K) to make it easier for consumers to understand . LEDs are subject to variations in the parameters of light color, luminous flux and forward voltage. To ensure a constant quality of light, LEDs in a batch are sorted using the binning process.

Light dosimeters are used to measure the exposure of an individual or a surface to light . In order to measure the specific amount of light that the human eye can perceive, an individual circadian measuring device, the daysimeter, was developed. It is a device that can measure and characterize light (intensity, spectrum, timing and duration), which is perceived by the eye and can thus influence the circadian rhythm of humans. The conversion factor for a melanopic illuminance on the eye is described in DIN SPEC 5031-100.

## Problems

### power consumption

As a measure to reduce CO 2 emissions from power plants that run on fossil fuels, there was a campaign to replace incandescent lamps and other inefficient light sources with fluorescent lamps and light-emitting diodes . In accordance with the Ecodesign Directive, incandescent lamps were phased out from September 1, 2009 until September 1, 2012. LED technology has established itself in almost all applications and can reduce energy consumption by more than 80%. While incandescent lamps only convert approx. 5% of the energy into light, the proportion of LEDs is approx. 30% and continues to rise sharply. Other studies mention significantly larger differences: According to this, the light output of conventional light bulbs is approx. 12 lm / watt, fluorescent lamps approx. 80 lm / watt and white LEDs 150 lm / watt and more. The graphic shows values ​​from 2018 and states 35% heat development and 250 lm / W for LEDs.

### physiology

Light has various effects on the body's own regulatory systems . Well-known effects are, for example, the influence on the synchronization of the internal clock and the release of the sleep hormone melatonin . Derived from these scientific findings, new lighting concepts for interiors were developed, such as Human Centric Lighting (HCL), which should avoid disturbances of biological processes through unnatural lighting as far as possible.

### Visual disturbance effects from light sources

Light sources can produce visual effects whose intensity or spectral distribution changes over time (English Temporal Light Artefacts, TLA). Examples are light flicker and the stroboscopic effect . These fluctuations in light intensity are often not consciously perceived, but they interfere with work on moving machines or cause nervousness. These undesirable effects can be minimized by technical coordination of the operating devices, LED modules and control devices / dimmers.

## Norms and other standards

Europe
• DIN EN 1838: Applied lighting technology - emergency lighting
• DIN EN 12193: Light and lighting - Sports facility lighting
• DIN EN 12464: Light and lighting - Lighting of workplaces
• DIN EN 12665: Light and lighting - Basic terms and criteria for specifying lighting requirements
• DIN EN 13032: Light and lighting - Measurement and display of photometric data from lamps and luminaires
• DIN EN 13201: Street lighting
• DIN EN 15193: Energy assessment of buildings - Energy requirements for lighting
• DIN EN 60529: Degrees of protection provided by the housing
• DIN EN 60598: luminaires
Germany
• DIN 5032: light measurement
• DIN 5034: Daylight indoors
• DIN 5035 : Lighting with artificial light
• DIN 67500: Lighting of lock systems
• DIN 67523: Lighting of pedestrian crossings with additional lighting
• DIN 67524: Lighting of road tunnels and underpasses
• DIN 67526-3: Sports facility lighting
• DIN SPEC 5031-100: Radiation physics in the optical field and lighting technology
• DIN SPEC 67600: Biologically effective lighting - planning recommendations

## literature

• Roland Baer: lighting technology. Basics. 3. Edition. Huss-Medien, Berlin 2006, ISBN 3-341-01497-7 .
• Klaus Daniels: Building Technology, A Guide for Architects and Engineers. Zurich / Munich 2000, ISBN 3-7281-2727-2 .
• Max Keller: Fascination Light, A Guide to Theater and Stage Lighting. Prestel Verlag, Munich 1999, ISBN 3-7913-2093-9 . (with very good background knowledge on the whole topic)
• Marie-Luise Lehmann: lighting design. Dietrich Reimer Verlag, 2002, ISBN 3-496-01252-8 .
• Roland Greule: Light and lighting in the media sector. Hanser Verlag, 2014, ISBN 978-3-446-43479-0 .

Commons : lighting  - collection of images, videos and audio files
Wiktionary: lighting  - explanations of meanings, word origins, synonyms, translations

## Individual evidence

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17. Color Temperature & Color Rendering Index DeMystified
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20. ^ New Approach Sheds Light on Ways Circadian Disruption Affects Human Health.
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22. cf. Armin Reller , Heike Holdinghausen: The gifted planet. Bonn 2014, pp. 202–204.
23. Vincenzo Balzani , Giacomo Bergamini, Paola Ceroni: Light: A Very Peculiar Reactant and Product. In: Angewandte Chemie International Edition . 54, Issue 39, 2015, pp. 11320–11337, doi: 10.1002 / anie.201502325 .
24. licht.wissen 17: LED: Basics - Application - Effect . licht.de, Frankfurt 2016, ISBN 978-3-945220-03-0 , p. 24.
25. ^ ZVEI (Ed.): Temporal Light Artefacts - TLA . Frankfurt 2017.