View source for Lighting

{{short description|Deliberate use of light to achieve practical or aesthetic effects}}
{{Distinguish|Lightning}}
{{Redirect-distinguish|Artificial light|Artificial Light (song)}}
[[File:Acropolis Of Athens Greece 04.jpg|thumb|[[Acropolis of Athens]] illuminated at night]]
[[File:Cherry blossoms with Isuzu-Chaya and Akafuku store at Night.jpg|thumb|Illuminated cherry blossoms, light from the shop windows, and Japanese lantern at night in [[Ise, Mie]], Japan]]

'''Lighting''' or '''illumination''' is the deliberate use of [[light]] to achieve practical or aesthetic effects. Lighting includes the use of both artificial [[light source]]s like lamps and light fixtures, as well as natural illumination by capturing [[daylight]]. [[Daylighting (architecture)|Daylighting]] (using windows, skylights, or [[Architectural light shelf|light shelves]]) is sometimes used as the main source of light during daytime in buildings. This can save [[energy]] in place of using artificial lighting, which represents a major component of energy consumption in buildings. Proper lighting can enhance task performance, improve the appearance of an area, or have positive psychological effects on occupants.

Indoor lighting is usually accomplished using [[light fixture]]s, and is a key part of [[interior design]]. Lighting can also be an intrinsic component of [[landscaping|landscape projects]].

==History==
{{For timeline|Timeline of lighting technology}}
With the [[Control of fire by early humans|discovery of fire]], the earliest form of artificial lighting used to illuminate an area were [[campfire]]s or [[torch]]es. As early as 400,000 years ago, fire was kindled in the caves of [[Peking Man]]. [[Prehistoric]] people used primitive [[oil lamp]]s to illuminate surroundings. These lamps were made from naturally occurring materials such as rocks, shells, horns and stones, were filled with [[grease (lubricant)|grease]], and had a [[fiber]] [[Candle wick|wick]]. Lamps typically used animal or vegetable fats as fuel. Hundreds of these lamps (hollow worked stones) have been found in the [[Lascaux]] caves in modern-day [[France]], dating to about 15,000 years ago. Oily animals (birds and fish) were also used as lamps after being threaded with a wick. [[Firefly|Fireflies]] have been used as lighting sources.<ref>{{Cite journal|date=1940-01-06|title=Oil-Lamps and Candles|url=http://dx.doi.org/10.1093/notesj/178.1.13-b|journal=Notes and Queries|doi=10.1093/notesj/178.1.13-b|issn=1471-6941|url-access=subscription}}</ref> [[Candle]]s and glass and pottery lamps were also invented.<ref>{{cite web|last=Williams|first=Ben|title=A History of Light and Lighting|url=http://www.mts.net/~william5/history/hol.htm|access-date=23 November 2012|year=1999|url-status=dead|archive-url=https://web.archive.org/web/20130125190606/http://www.mts.net/~william5/history/hol.htm|archive-date=25 January 2013}}</ref> [[Chandelier]]s were an early form of "[[light fixture]]".

A major reduction in the cost of lighting occurred with the discovery of [[whale oil]].<ref name="planet_money">{{Cite episode |title=The History of Light |url=https://www.npr.org/blogs/money/2014/04/25/306862378/episode-534-the-history-of-light |access-date=June 20, 2016 |series=Planet Money |publisher=NPR |date=April 25, 2014 |number=534}}</ref> The use of whale oil declined after [[Abraham Gesner]], a Canadian geologist, first refined [[kerosene]] in the 1840s, allowing brighter light to be produced at substantially lower cost.<ref name="Dolin">{{Cite book|author=Eric Jay Dolin|title=Leviathan: The History of Whaling in America|publisher=W.W. Norton & Co.|date=2007|pages=339–40}}</ref> In the 1850s, the price of whale oil dramatically increased (more than doubling from 1848 to 1856) due to shortages of available whales, hastening whale oil's decline.<ref name="Dolin"/> By 1860, there were 33 kerosene plants in the United States, and Americans spent more on gas and kerosene than on whale oil.<ref name="Dolin"/> The final death knell for whale oil was in 1859, when [[crude oil]] was discovered and the [[petroleum industry]] arose.<ref name="Dolin"/>
[[File:Finland, Porvoo, Old Town by night, Teemu Eskola.jpg|thumb|Dim night lighting for the old warehouses along the river in the old town of [[Porvoo]], [[Finland]]]]

[[Gas lighting]] was economical enough to power street lights in major cities starting in the early 1800s, and was also used in some commercial buildings and in the homes of wealthy people. The [[gas mantle]] boosted the luminosity of utility lighting and of kerosene lanterns. The next major drop in price came about in the 1880s with the introduction of [[electricity|electric lighting]] in the form of [[Arc lamp|arc lights]] for large space and [[street lighting]], followed by [[incandescent light bulb]]-based utilities for indoor and outdoor lighting.<ref name="planet_money" /><ref>{{Cite web |title=The First Form of Electric Light |url=http://edisontechcenter.org/ArcLamps.html |access-date=2025-05-10 |website=edisontechcenter.org}}</ref> Over time, electric lighting became ubiquitous in developed countries.<ref name="Kirtley2011">{{cite book|author=James L. Kirtley|title=Electric Power Principles: Sources, Conversion, Distribution and Use|url=https://books.google.com/books?id=YY9TGX11En8C&pg=PT11|date=5 July 2011|publisher=John Wiley & Sons|isbn=978-1-119-95744-7|pages=11–}}</ref> [[Segmented sleep]] patterns disappeared, improved nighttime lighting made more activities possible at night, and more [[street lights]] reduced urban crime.<ref>{{cite book |title=Criminology: Theory, Research, and Policy |first1=Gennaro F. |last1=Vito |first2=Jeffrey R. |last2=Maahs |publisher=Jones & Bartlett |year=2011 |edition=revised |isbn=9780763766658 |page=[https://archive.org/details/criminologytheor0000vito/page/70 70] |url=https://archive.org/details/criminologytheor0000vito/page/70 }}</ref><ref>{{cite book |title=Crime and Everyday Life |first1=Marcus |last1=Felson |first2=Rachel L. |last2=Boba |publisher=SAGE |year=2009 |isbn=9781483342658 |page=186}}</ref><ref>{{cite book |title=Street lighting, energy conservation and crime |publisher=United States Law Enforcement Assistance Administration, Emergency Energy Committee, U.S. Dept. of Justice |year=1974 |quote=The public [has] a general feeling that street lights have a deterrent effect on street crimes. This effect is somewhat substantiated by research conducted by LEAA and by the fact that various communities which have installed improved street lighting in certain areas have reported reductions in the rate of street crime.}}</ref>

==Fixtures==
{{main|Light fixture}}

[[Lighting fixture]]s come in a wide variety of styles for various functions. The most important functions are as a holder for the light source, to provide directed light and to avoid [[visual glare]].<ref>{{cite journal |last1= Kent |first1= Michael | last2= Fotios | first2 = Steve | last3= Altomonte | first3= Sergio |date= 2019 |title= An Experimental Study on the Effect of Visual Tasks on Discomfort Due to Peripheral Glare |journal= LEUKOS | volume= 15 | issue= 1 | pages= 17–28 | doi= 10.1080/15502724.2018.1489282 | doi-access= free }}</ref> Some are very plain and functional, while some are pieces of art in themselves. Nearly any material can be used, so long as it can tolerate the excess heat and is in keeping with safety codes. An important property of light fixtures is the [[luminous efficacy]] or [[wall-plug efficiency]], meaning the amount of usable light emanating from the fixture per used energy, usually measured in [[Lumen (unit)|lumen]] per [[watt]]. A fixture using replaceable light sources can also have its efficiency quoted as the percentage of light passed from the "bulb" to the surroundings. The more [[transparency and translucency|transparent]] the lighting fixtures are, the higher efficacy. [[Shadow|Shading]] the light will normally decrease efficacy but increase the directionality and the [[visual comfort probability]].

[[Color temperature]] for white light sources also affects their use for certain applications. The color temperature of a white light source is the temperature in [[kelvin]]s of a theoretical [[black body]] emitter that most closely matches the spectral characteristics ([[spectral power distribution]]) of the lamp. An incandescent bulb has a color temperature around 2800 to 3000 kelvins; daylight is around 6400 kelvins. Lower color temperature lamps have relatively more energy in the yellow and red part of the visible spectrum, while high color temperatures correspond to lamps with more of a blue-white appearance.  For critical inspection or color matching tasks, or for retail displays of food and [[clothing]], the color temperature of the lamps will be selected for the best overall lighting effect.{{Citation needed|date=January 2023}}

===Types===
{{see also|List of types of lighting}}
[[File:SameEyes4.jpg|thumb|A demonstration of the effects of different kinds of lighting{{clarification needed|reason=what kinds?|date=June 2024}}]]

Lighting is classified by intended use as general, accent, or task lighting, depending largely on the distribution of the light produced by the fixture.

* [[Task lighting]] is mainly functional and is usually the most concentrated, for purposes such as [[reading (activity)|reading]] or [[inspection]] of materials. For example, reading poor-quality reproductions may require task lighting levels up to 1500 [[lux]] (140 [[footcandle]]s), and some inspection tasks or [[surgical]] procedures require even higher levels.
* [[Accent lighting]] is mainly decorative, intended to highlight [[picture]]s, [[plant]]s, or other elements of [[interior design]] or [[landscaping]].
[[File:White Ceiling Light.jpg|thumb|A ceiling light fixture]]
* General lighting (sometimes referred to as ambient light) fills in between the two and is intended for general illumination of an area. Indoors, this would be a basic [[Lamp (electrical component)|lamp]] on a table or floor, or a fixture on the [[ceiling]]. Outdoors, general lighting for a [[parking lot]] may be as low as 10-20 lux (1-2 footcandles) since [[pedestrian]]s and [[motorist]]s already used to the dark will need little light for crossing the area.

===Methods===

* [[Downlight]]ing is most common, with fixtures on or recessed in the ceiling casting light downward. This tends to be the most used method, used in both offices and homes. Although it is easy to design, it has dramatic problems with glare and excess energy consumption due to large number of fittings.<ref name="ReferenceA">{{cite journal | last1 = Li | first1 = D | last2 = Cheung | first2 = K | last3 = Wong | first3 = S | last4 = Lam | first4 = T | year = 2010 | title = An analysis of energy-efficient light fittings and lighting controls | journal = Applied Energy | volume = 87 | issue = 2| pages = 558–567 | doi=10.1016/j.apenergy.2009.07.002| bibcode = 2010ApEn...87..558L }}</ref> The introduction of [[LED lighting]] has greatly improved this by approx. 90% when compared to a halogen downlight or spotlight. LED lamps or bulbs are now available to retro fit in place of high energy consumption lamps.
* [[Uplight]]ing is less common, often used to bounce indirect light off the ceiling and back down. It is commonly used in lighting applications that require minimal glare and uniform general illuminance levels. Uplighting (indirect) uses a diffuse surface to reflect light in a space and can minimize disabling glare on [[computer displays]] and other dark glossy surfaces. It gives a more uniform presentation of the light output in operation. However indirect lighting is completely reliant upon the reflectance value of the surface. While indirect lighting can create a diffused and shadow free light effect it can be regarded as an uneconomical lighting principle.<ref name="Kim W 1023">{{cite journal | last1 = Kim | first1 = W | last2 = Han | first2 = H | last3 = Kim | first3 = J | year = 2009 | title = The position index of a glare source at the borderline between comfort and discomfort (BCD) in the whole visual field | journal = Building & Environment | volume = 44 | issue = 5| pages = 1017–1023 | doi=10.1016/j.buildenv.2008.07.007| bibcode = 2009BuEnv..44.1017K }}</ref><ref name="M. Velds 2002 pp. 95">{{cite journal | last1 = Velds | first1 = M. | year = 2002 | title = User acceptance studies to evaluate discomfort glare in daylit room | journal = Solar Energy | volume = 73 | issue = 2| pages = 95–103 | doi=10.1016/s0038-092x(02)00037-3| bibcode = 2002SoEn...73...95V }}</ref>
* Front lighting is also quite common, but tends to make the subject look flat as its casts almost no visible shadows. Lighting from the side is the less common, as it tends to produce [[glare (vision)|glare]] near [[Human eye|eye]] level.
*[[Backlighting (lighting design)|Backlight]]ing either around or through an object is mainly for accent. Backlighting is used to illuminate a background or backdrop. This adds depth to an image or scene. Others use it to achieve a more dramatic effect.

===Forms of lighting===

====Indoor lighting====

[[File:BWLight.jpg|thumb|Wall-mounted light with shadows]]

Forms of lighting include [[alcove (architecture)|alcove]] lighting, which like most other uplighting is indirect. This is often done with [[fluorescent lighting]] (first available at the [[1939 World's Fair]]) or [[rope light]], occasionally with [[neon lighting]], and recently with [[LED Strip Light|LED strip lighting]]. It is a form of [[backlighting]].

[[Soffit]] or close to wall lighting can be general or a decorative wall-wash, sometimes used to bring out texture (like [[stucco]] or [[plaster]]) on a wall, though this may also show its [[wikt:defect|defects]] as well. The effect depends heavily on the exact type of lighting source used. [[Recessed lighting]] (often called "pot lights" in [[Canada]], "can lights" or 'high hats" in the [[United States|US]]) is popular, with fixtures mounted into the ceiling structure so as to appear flush with it.<ref>{{Cite web |date=2024-12-23 |title=What is Recessed Lighting? What Do You Know? |url=https://comiled.com/blogs/news/what-is-recessed-lighting |access-date=2025-04-15 |website=ComiLED |language=en}}</ref> These downlights can use narrow beam spotlights, or wider-[[angle]] [[Stage lighting instrument#Floodlights|floodlight]]s, both of which are bulbs having their own [[mirror|reflector]]s.  There are also downlights with internal reflectors designed to accept common 'A' lamps (light bulbs) which are generally less costly than reflector lamps. Downlights can be incandescent, fluorescent, [[High-intensity discharge lamp|HID (high intensity discharge)]] or [[LED]]. [[Track lighting]], invented by [[Lightolier]],<ref>{{Cite book|title = The New York Times Practical Guide to Practically Everything: The Essential Companion for Everyday Life|last = Bernstein|publisher = St. Martin's Press|year = 2006|isbn = 978-0312353889|pages = [https://archive.org/details/newyorktimesprac00bern/page/424 424]|url-access = registration|url = https://archive.org/details/newyorktimesprac00bern/page/424}}</ref> was popular at one period of time because it was much easier to install than recessed lighting, and individual fixtures are decorative and can be easily aimed at a [[wall]]. It has regained some popularity recently in low-voltage tracks, which often look nothing like their predecessors because they do not have the safety issues that line-voltage systems have, and are therefore less bulky and more ornamental in themselves. A master [[transformer]] feeds all of the fixtures on the track or rod with 12 or 24 volts, instead of each light fixture having its own line-to-low voltage transformer. There are traditional spots and floods, as well as other small hanging fixtures. A modified version of this is [[cable lighting]], where lights are hung from or clipped to bare [[metal]] [[Wire rope|cables]] under [[tension (mechanics)|tension]]. A [[Sconce (light fixture)|sconce]] is a wall-mounted fixture, particularly one that shines up and sometimes down as well. A [[torchère]] is an uplight intended for ambient lighting. It is typically a floor lamp but may be wall-mounted like a sconce. Further interior light fixtures include chandeliers, pendant lights, ceiling fans with lights, close-to-ceiling or flush lights, and various types of lamps<ref name="interiorlights">{{cite web|title=Living Room Lighting: 20 Powerful Ideas to Improve your Lighting |date=June 1, 2018 |first1=Paul |last1=West |url=https://www.lampsusa.com/blogs/how-to-and-tips/20-powerful-ways-to-improve-your-living-room-lighting|publisher=Lamps USA|access-date=6 June 2018 |url-status=live |archive-url=https://web.archive.org/web/20190203165213/https://www.lampsusa.com/blogs/how-to-and-tips/20-powerful-ways-to-improve-your-living-room-lighting |archive-date= Feb 3, 2019 }}</ref><ref>{{Cite web |date=2025-02-11 |title=KLOE Lighting |url=https://kloelighting.com |access-date=2025-05-10 |website=KLOE LIGHTING |language=en}}</ref> The portable or table lamp is probably the most common fixture, found in many homes and [[office]]s. The standard lamp and shade that sits on a table is general lighting, while the desk lamp is considered task lighting. [[magnification|Magnifier]] lamps are also task lighting.

[[File:Fountain Europe Square Moscow.jpg|thumb|Animated fountain in [[Moscow]]'s [[Square of Europe]], lit at night]]

The [[illuminated ceiling]] was once popular in the 1960s and 1970s but fell out of favor after the 1980s. This uses [[Diffuser (optics)|diffuser]] panels hung like a [[suspended ceiling]] below fluorescent lights, and is considered general lighting. Other forms include neon, which is not usually intended to illuminate anything else, but to actually be an artwork in itself. This would probably fall under accent lighting, though in a dark [[nightclub]] it could be considered general lighting.

In a [[movie theater]], steps in the aisles are usually marked with a row of small lights for convenience and safety, when the film has started and the other lights are off. Traditionally made up of small low wattage, low-voltage lamps in a track or translucent tube, these are rapidly being replaced with LED based versions.{{Citation needed|date=April 2025}}

====Outdoor lighting====
[[File:Highway 401 Night Lapse Busy.jpg|left|thumb|[[High-mast lighting|High mast lighting]] along [[Ontario Highway 401|Highway 401]] in [[Ontario]], Canada]]
Outdoor light is used for a number of purposes, including lighting areas (functional lighting), advertising, and decoration. A large-scale study in [[Germany]] in 2021 found that the most common light source in public areas was leakage from private windows (48%), followed by [[Street light|street and path lights]] (12.8%), commercial shop windows (7.4%), signs (5.6%), and lights mounted on the exterior sides of buildings (5.3%).<ref>{{Cite journal |last=Team Nachtlichter |last2=Nachtlichter |first2=Team |last3=Tegeler |first3=Achim |last4=Marz |first4=Aleksander |last5=Gokus |first5=Andrea |last6=Hänel |first6=Andreas |last7=Rienow |first7=Andreas |last8=Ruby |first8=Andreas |last9=Glinka |first9=Anja |last10=Kyba |first10=Anna Marie |last11=Dröge-Rothaar |first11=Arne |last12=Schwiesow |first12=Axel |last13=Gillen |first13=Benno |last14=von Heereman |first14=Bettine |last15=Kuechly |first15=Brita |date=2025-06-16 |title=Citizen science illuminates the nature of city lights |url=https://www.nature.com/articles/s44284-025-00239-5 |journal=Nature Cities |language=en |volume=2 |issue=6 |pages=496–505 |doi=10.1038/s44284-025-00239-5 |issn=2731-9997}}</ref>

Street lights are used to light roadways and walkways at night. [[Floodlights (sport)|Floodlights]] can be used to illuminate work zones<ref>{{Cite book |last1=Transportation |first1=Department of |url=https://books.google.com/books?id=-UpgOXdYEOYC&q=Floodlights+can+be+used+to+illuminate+large+areas+nighttime+hours&pg=PT504 |title=Manual on Uniform Traffic Control Devices: Inserts Only |last2=Administration |first2=Federal Highway |date=November 2003 |publisher=Claitor's Law Books and Publishing |isbn=9781579809294}}</ref> or outdoor playing fields during nighttime hours.<ref>{{Cite book |url=https://books.google.com/books?id=yFklAQAAIAAJ&q=Flood+Lights+can+be+used+to+illuminate+playing+fields+nighttime+hours |title=Draft Revised Environmental Impact Report for Scotts Valley High School--Glenwood Site |date=1997 |publisher=Denise Duffy & Associates}}</ref><ref>{{Cite book |last1=Felber |first1=Bill |url=https://books.google.com/books?id=rdgAAgAAQBAJ&q=Flood+Lights+can+be+used+to+illuminate+playing+fields+nighttime+hours&pg=PA125 |title=Inventing Baseball: The 100 Greatest Games that Shaped the 19th Century |last2=Fimoff |first2=Mark |last3=Levin |first3=Len |last4=Mancuso |first4=Peter |date=April 2013 |publisher=SABR |isbn=9781933599427}}</ref>

[[File:Floodlights.jpg|thumb|[[Floodlights (sport)|Floodlights]] are used to illuminate outdoor playing fields or work zones during nighttime.]]


[[Street light#Beacon lights|Beacon lights]] are positioned at the intersection of two roads to aid in navigation. [[Security lighting]] is installed with the intention of preventing crime, and is often extremely bright. Entry lights are often used outside to illuminate and signal the entrance to a property, and are sometimes installed for decorative purposes.<ref>DELTA Snapshot: Outdoor Entry Lighting. Issue 11. Lighting Research Center. Found online at: http://www.lrc.rpi.edu/programs/delta/pdf/OutdoorEntry.pdf [last accessed 13 April 2010]</ref> Underwater accent lighting is sometimes used for koi ponds, fountains, swimming pools and the like.

All forms of outdoor lighting contribute to [[light pollution]], although some lighting practices are associated with greater environmental impacts than others.<ref>{{Cite journal |last=Luginbuhl |first=Christian B. |last2=Duriscoe |first2=Dan M. |last3=Moore |first3=Chadwick W. |last4=Richman |first4=Angela |last5=Lockwood |first5=G. Wesley |last6=Davis |first6=Donald R. |date=2009 |title=From the Ground Up II: Sky Glow and Near-Ground Artificial Light Propagation in Flagstaff, Arizona |url=http://iopscience.iop.org/article/10.1086/597626 |journal=Publications of the Astronomical Society of the Pacific |language=en |volume=121 |issue=876 |pages=204–212 |doi=10.1086/597626 |issn=0004-6280}}</ref>

[[File:SDC Lit at Night.jpg|thumb|The decks and [[gangway (nautical)|gangway]] of tugboat ''[[Samuel de Champlain (tugboat)|Samuel de Champlain]]'' illuminated at night while docked at a shipyard for the purposes of safety and security]]

==Vehicle use==
{{main|Automotive lighting}}

[[Vehicles]] typically include [[headlamp]]s and tail lights.  Headlamps are [[white]] or [[selective yellow]] lights placed in the front of the vehicle, designed to illuminate the upcoming road and to make the vehicle more visible. Many manufactures are turning to LED headlights as an energy-efficient alternative to traditional headlamps.<ref>Van Derlofske, J, JD Bullough, J Watkinson. 2005. Spectral Effects of LED Forward Lighting. TLA 2005-02. Lighting Research Center. Found online at: http://www.lrc.rpi.edu/programs/transportation/TLA/pdf/TLA-2005-02.pdf [last accessed 13 April 2010]</ref> Tail and brake lights are [[red]] and emit light to the rear so as to reveal the vehicle's direction of travel to following drivers. White rear-facing reversing lamps indicate that the vehicle's transmission has been placed in the reverse gear, warning anyone behind the vehicle that it is moving backwards, or about to do so. Flashing turn signals on the front, side, and rear of the vehicle indicate an intended change of position or direction. In the late 1950s, some automakers began to use [[Electroluminescence|electroluminescent]] technology to [[backlight]] their cars' [[speedometer]]s and other gauges or to draw attention to [[logo]]s or other decorative elements.

==Lamps==
{{main|Lamp (electrical component)}}
Commonly called 'light bulbs', [[Lamp (electrical component)|lamps]] are the removable and replaceable part of a light fixture, which converts electrical energy into [[electromagnetic radiation]]. While lamps have traditionally been rated and marketed primarily in terms of their power consumption, expressed in [[watt]]s, proliferation of lighting technology beyond the [[incandescent light bulb]] has eliminated the correspondence of wattage to the amount of light produced. For example, a 60&nbsp;W incandescent light bulb produces about the same amount of light as a 13&nbsp;W [[compact fluorescent lamp]]. Each of these technologies has a different [[Luminous efficacy|efficacy]] in converting electrical energy to [[visible light]]. Visible light output is typically measured in [[Lumen (unit)|lumen]]s. This unit only quantifies the visible radiation, and excludes invisible infrared and ultraviolet light. A wax candle produces on the close order of 13 lumens, a 60 watt incandescent lamp makes around 700 lumens, and a 15-watt compact fluorescent lamp produces about 800 lumens, but actual output varies by specific design.<ref>Roger Fouquet, ''Heat, power and light: revolutions in energy services'',  Edward Elgar Publishing, 2008 {{ISBN|1-84542-660-6}}, page 411</ref> Rating and marketing emphasis is shifting away from wattage and towards lumen output, to give the purchaser a directly applicable basis upon which to select a lamp.


<!-- integration of lighting and ventilation system-->Lamp types include:
* [[Electrical ballast|Ballast]]: A ballast is an auxiliary piece of equipment designed to start and properly control the flow of [[Electric power#Mathematics of electric power|power]] to discharge light sources such as [[Fluorescent lamp|fluorescent]] and [[Metal-halide lamp|high intensity discharge]] (HID) lamps. Some lamps require the ballast to have thermal protection.
* [[Fluorescent lamp|fluorescent]] light: A tube coated with [[phosphor]] containing low pressure [[mercury (element)|mercury]] vapor that produces white light.
* [[Halogen lamp|Halogen]]: Incandescent lamps containing halogen gases such as iodine or bromine, increasing the efficacy of the lamp versus a plain incandescent lamp.
* [[Neon lamp|Neon]]: A low pressure gas contained within a glass tube; the color emitted depends on the gas.
* [[Light-emitting diode]]s: Light-emitting diodes (LED) are solid state devices that emit light by dint of the movement of electrons in a [[semiconductor]] material.<ref>{{cite journal | year = 2004 | title = Leading luminaries | journal = Cabinet Maker | volume = 5419 | pages = 21–22 }}</ref>
* [[Compact fluorescent lamp]]s: CFLs are designed to replace incandescent lamps in existing and new installations.<ref>Khan N, Abas N. Comparative study of energy saving light sources. Renewable & Sustainable Energy Reviews [serial online].</ref><ref>{{cite journal | year = 2008 | title = How to power an ENERGY-EFFICIENT LIGHT | journal = Machine Design | volume = 80 | issue = 12| pages = 51–53 }}</ref>

==Design and architecture==

===Architectural lighting design===
{{main|Architectural lighting design}}

[[File:Giovanni Paolo Panini - Interior of the Pantheon, Rome - Google Art Project.jpg|thumb|upright|Lighting without windows: The [[Pantheon, Rome|Pantheon]] in the 18th century, painted by [[Giovanni Paolo Panini]].<ref>[http://www.liechtensteinmuseum.at/en/pages/artbase_main.asp?module=browse&action=m_work&lang=en&sid=31032196&oid=W-147200412195342017 Another view of the interior by Panini (1735), Liechtenstein Museum, Vienna] {{webarchive|url=https://web.archive.org/web/20110928031043/http://www.liechtensteinmuseum.at/en/pages/artbase_main.asp?module=browse&action=m_work&lang=en&sid=31032196&oid=W-147200412195342017 |date=2011-09-28 }}</ref>]]

Lighting design as it applies to the built environment is known as 'architectural lighting design'. Lighting of structures considers aesthetic elements as well as practical considerations of quantity of light required, occupants of the structure, energy efficiency, and cost. Artificial lighting takes into account the amount of daylight received in a space by using [[daylight factor]] calculations. For simple installations, hand calculations based on tabular data are used to provide an acceptable lighting design. More critical or complex designs now routinely use computer software such as [[Radiance (software)|Radiance]]<ref>{{Cite web |title=Radiance |url=https://www.energy.gov/eere/buildings/articles/radiance |access-date=2024-08-27 |website=Energy.gov |language=en}}</ref> for mathematical modeling, which can allow an architect to quickly and accurately evaluate the benefit of a proposed design.

In some instances, the materials used on walls and furniture play a key role in the lighting effect.  For example, dark paint tends to absorb light, making the room appear smaller and more dim than it is, whereas light paint does the opposite. Other reflective surfaces also have an effect on lighting design.<ref name="M. Velds 2002 pp. 95"/><ref>{{cite journal | last1 = Israel | first1 = C | last2 = Bleeker | first2 = N | year = 2008 | title = Sustainable Lighting Strategies | journal = Electrical Wholesaling | volume = 89 | issue = 9 | pages = 38–41 }}</ref>

==On stage and set==
{{Main|Stage lighting}}
{{Unreferenced section|date=February 2012}}
[[File:Female in red pullover and blue jeans -coloured lights-2Nov2003.jpg|thumb|Lighting and shadows]]
[[File:Ivan-rogue-hybrid.jpg|thumb|Moving heads in a photo studio set]]
[[File:ScaryVampire.JPG|thumb|Illuminating a subject from beneath can create a heightened dramatic effect.]]

Lighting illuminates the performers and artists in a live theatre, dance, or musical performance, and is selected and arranged to create dramatic effects. Stage lighting uses general illumination technology in devices configured for easy adjustment of their output characteristics.{{Citation needed|date=February 2012}} The setup of stage lighting is tailored for each scene of each production. Dimmers, colored filters, reflectors, lenses, motorized or manually aimed lamps, and different kinds of flood and spot lights are among the tools used by a stage [[lighting designer]] to produce the desired effects. A set of lighting cues are prepared so that the lighting operator can control the lights in step with the performance; complex theatre lighting systems use computer control of lighting instruments.

Motion picture and television production use many of the same tools and methods of stage lighting. Especially in the early days of these industries, very high light levels were required and heat produced by lighting equipment presented substantial challenges. Modern cameras require less light, and modern light sources emit less heat.

==Measurement==
{{main|Photometry (optics)}}

Measurement of light or [[Photometry (optics)|photometry]] is generally concerned with the amount of useful light falling on a surface and the amount of light emerging from a lamp or other source, along with the colors that can be rendered by this light. The human eye responds differently to light from different parts of the visible spectrum, therefore photometric measurements must take the [[luminosity function]] into account when measuring the amount of useful light. The basic [[SI]] unit of measurement is the [[candela]] (cd), which describes the luminous intensity, all other photometric units are derived from the candela. [[Luminance]] for instance is a measure of the density of luminous intensity in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given [[solid angle]]. The SI unit for luminance is [[candela]] per [[square metre]] (cd/m<sup>2</sup>). The [[CGS]] unit of luminance is the [[stilb (luminance)|stilb]], which is equal to one candela per square centimetre or 10&nbsp;kcd/m<sup>2</sup>. The amount of useful light emitted from a source or the [[luminous flux]] is measured in [[lumen (unit)|lumen]] (lm).

The [[International System of Units|SI]] unit of [[illuminance]] and [[luminous emittance]], being the luminous power per area, is measured in [[Lux]]. It is used in [[photometry (optics)|photometry]] as a measure of the intensity, as perceived by the human eye, of [[light]] that hits or passes through a surface. It is analogous to the [[radiometry|radiometric]] unit watts per square metre, but with the power at each [[wavelength]] weighted according to the [[luminosity function]], a standardized model of human visual brightness perception. In English, "lux" is used in both singular and plural.<ref>{{Cite journal |date=2009-07-02 |title=Special Publication 811 |url=https://www.nist.gov/pml/special-publication-811 |journal=NIST |language=en}}</ref>

Visual comfort often entails the measurement of subjective evaluations.<ref>{{cite journal |last1= Fotios |first1= Steve | last2= Kent | first2= Michael | date= 2021 |title= Measuring Discomfort from Glare: Recommendations for Good Practice | url= https://www.tandfonline.com/doi/full/10.1080/15502724.2020.1803082?src=recsys |journal= LEUKOS |volume= 17 |issue= 4 |pages= 338–358 | doi= 10.1080/15502724.2020.1803082 |s2cid= 225293753 | access-date= 2021-11-01}}</ref> Several measurement methods have been developed to control glare resulting from indoor lighting design. The [[Unified Glare Rating#Unified glare rating|Unified Glare Rating]] (UGR), the Visual Comfort Probability, and the Daylight Glare Index are some of the most well-known methods of measurement. In addition to these new methods, four main factors influence the degree of discomfort glare; the luminance of the glare source, the solid angle of the glare source, the background luminance, and the position of the glare source in the field of view must all be taken into account.<ref name="Kim W 1023"/><ref>W. Kim and Y. Koga, "Effect of local background luminance on discomfort glare, ''Building Environ'' 2004; 38, pp.</ref>

===Color properties===
[[File:Leppävaaran Torni illuminated 1.jpg|thumb|upright|The ''[[Leppävaara tower|Leppävaaran Torni]]'' building in [[Leppävaara]], [[Espoo]], Finland, illuminated with colorful lights in 2017]]
To define light source color properties, the lighting industry predominantly relies on two metrics, [[correlated color temperature]] (CCT),  commonly used as an indication of the apparent "warmth" or "coolness" of the light emitted by a source, and [[color rendering index]] (CRI), an indication of the light source's ability to make objects appear natural. However, these two metrics, developed in the last century, are facing increased challenges and criticisms as new types of light sources, particularly light-emitting diodes (LEDs), become more prevalent in the market.

For example, in order to meet the expectations for good color rendering in retail applications, research<ref>ASSIST recommends: Guide to Light and Color in Retail Merchandising. 2010. Volume 8, Issue 1. Available online at: {{cite web|url=http://www.lrc.rpi.edu/programs/solidstate/assist/recommends/lightcolor.asp |title=ASSIST recommends: Light Source Color for Retail Merchandising &#124; ASSIST Program &#124; Solid State Lighting &#124; Programs &#124; LRC |access-date=2011-05-13 |url-status=dead |archive-url=https://web.archive.org/web/20110718171338/http://www.lrc.rpi.edu/programs/solidstate/assist/recommends/lightcolor.asp |archive-date=2011-07-18 }}</ref> suggests using the well-established CRI along with another metric called gamut area index (GAI). GAI represents the relative separation of object colors illuminated by a light source; the greater the GAI, the greater the apparent saturation or vividness of the object colors. As a result, light sources which balance both CRI and GAI are generally preferred over ones that have only high CRI or only high GAI.<ref>ASSIST recommends: Recommendations for Specifying Color Properties of Light Sources for Retail Merchandising. 2010. Volume 8, Issue 2. Available online at: {{cite web|url=http://www.lrc.rpi.edu/programs/solidstate/assist/recommends/lightcolor.asp |title=ASSIST recommends: Light Source Color for Retail Merchandising &#124; ASSIST Program &#124; Solid State Lighting &#124; Programs &#124; LRC |access-date=2011-05-13 |url-status=dead |archive-url=https://web.archive.org/web/20110718171338/http://www.lrc.rpi.edu/programs/solidstate/assist/recommends/lightcolor.asp |archive-date=2011-07-18 }}</ref>

===Light exposure===
Typical measurements of light have used a Dosimeter. Dosimeters measure an individual's or an object's exposure to something in the environment, such as light dosimeters and ultraviolet dosimeters.

In order to specifically measure the amount of light entering the eye, personal circadian light meter called the Daysimeter has been developed.<ref>{{cite journal | pmc = 2430544 | pmid=18510756 | doi=10.1186/1740-3391-6-7 | volume=6 | title=A new approach to understanding the impact of circadian disruption on human health | year=2008 | journal=J Circadian Rhythms | pages=7 | last1 = Rea | first1 = MS | last2 = Bierman | first2 = A | last3 = Figueiro | first3 = MG | last4 = Bullough | first4 = JD | doi-access=free }}</ref> This is the first device created to accurately measure and characterize light (intensity, spectrum, timing, and duration) entering the eye that affects the human body's clock.

The small, head-mounted device measures an individual's daily rest and activity patterns, as well as exposure to short-wavelength light that stimulates the circadian system. The device measures activity and light together at regular time intervals and electronically stores and logs its [[operating temperature]]. The Daysimeter can gather data for up to 30 days for analysis.<ref>Lighting Research Center Website: New approach sheds light on ways circadian disruption affects human health. Found online at: {{cite web|url=http://www.lrc.rpi.edu/programs/lightHealth/projects/CircadianHealth.asp?id%3D167 |title=Light and Health &#124; Research Programs &#124; LRC |access-date=2016-02-07 |url-status=dead |archive-url=https://web.archive.org/web/20100609225907/http://www.lrc.rpi.edu/programs/lightHealth/projects/CircadianHealth.asp?id=167 |archive-date=2010-06-09 }} [last accessed 13 April 2010]</ref>

==Energy consumption==
Several strategies are available to minimize energy requirements for lighting a building:

* Specification of illumination requirements for each given use area
* Analysis of lighting quality to ensure that adverse components of lighting (for example, glare or incorrect [[color spectrum]]) are not biasing the design
* Integration of space planning and interior architecture (including choice of interior surfaces and room geometries) to lighting design
* Design of time of day use that does not expend unnecessary energy
* Selection of [[Light fixture|fixture]]s and lamps that reflect best available technology for [[energy conservation]]
* Training of building occupants to use lighting equipment in most efficient manner
* Maintenance of lighting systems to minimize energy wastage
* Use of natural light
** Some big box stores were being built from 2006 on with numerous plastic bubble skylights, in many cases completely obviating the need for interior artificial lighting for many hours of the day.
** In countries where indoor lighting of simple dwellings is a significant cost, "[[Moser lamp]]s", plastic water-filled transparent drink bottles fitted through the roof, provide the equivalent of a 40- to 60-watt incandescent bulb each during daylight.<ref>{{Cite news |date=2013-08-12 |title=Alfredo Moser: Bottle light inventor proud to be poor |url=https://www.bbc.co.uk/news/magazine-23536914 |access-date=2025-05-10 |work=BBC News |language=en-GB}}</ref>
* [[Rolling blackout|Load shedding]] can help reduce the power requested by individuals to the main power supply. Load shedding can be done on an individual level, at a building level, or even at a regional level.

Specification of illumination requirements is the basic concept of deciding how much illumination is required for a given task. Clearly, much less light is required to illuminate a hallway compared to that needed for a [[word processing]] work station.  Generally speaking, the [[energy]] expended is proportional to the design illumination level. For example, a lighting level of 400 [[lux]] might be chosen for a work environment involving meeting rooms and conferences, whereas a level of 80 lux could be selected for building hallways.<ref>{{Cite book|author=Australian Greenhouse Office|title=Working Energy Resource and Training Kit: Lighting |date=May 2005|chapter-url=http://www.greenhouse.gov.au/lgmodules/wep/lights/index.html|chapter=Chapter 5: Assessing lighting savings |access-date=2007-03-17 | archive-url = https://web.archive.org/web/20070415151053/http://www.greenhouse.gov.au/lgmodules/wep/lights/training/training9.html | archive-date=2007-04-15}}</ref><ref>{{cite web |url=http://www.scopecalc.com/ |title=Low-Light Performance Calculator |access-date=2015-05-19 |archive-url=https://web.archive.org/web/20130615074318/http://scopecalc.com/ |archive-date=2013-06-15 |url-status=dead }}</ref><ref>{{cite web |url=http://www.resourcesmart.vic.gov.au/documents/lux_meter.pdf |title=Lux Meter |website=ResourceSmart.Vic.gov.au |publisher=Sustainability Victoria |date=April 2010 |archive-url=https://web.archive.org/web/20110707054658/http://www.resourcesmart.vic.gov.au/documents/lux_meter.pdf |archive-date=7 July 2011 |access-date=2021-02-08 }}</ref><ref>{{cite web |url=http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10630 |title=Illumination. - 1926.56 |work=Regulations (Standards - 29 CFR) |publisher=Occupational Safety and Health Administration, US Dept. of Labor| archive-url =https://web.archive.org/web/20090508051301/http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10630| archive-date=8 May 2009}}</ref><ref>European law UNI EN 12464</ref> If the hallway standard simply emulates the conference room needs, then much more energy will be consumed than is needed.

===Lighting control systems===
{{Main|Lighting control system}}

Lighting control systems reduce energy usage and cost by helping to provide light only when and where it is needed.  Lighting control systems typically incorporate the use of time schedules, occupancy control, and photocell control (i.e. [[daylight harvesting]]). Some systems also support [[demand response]] and will automatically dim or turn off lights to take advantage of [[electric utility|utility]] incentives.  Lighting control systems are sometimes incorporated into larger [[Building automation|building automation systems]].

Many newer control systems are using [[wireless mesh network|wireless mesh]] open standards (such as [[Zigbee]]),<ref>{{cite journal|last=Bellido-Outeirino|first=Francisco J.|title=Building lighting automation through the integration of DALI with wireless sensor networks|journal=IEEE Transactions on Consumer Electronics|date=February 2012|volume=58|issue=1|pages=47–52|doi=10.1109/TCE.2012.6170054|s2cid=695261}}</ref> which provides benefits including easier installation (no need to run control wires) and interoperability with other standards-based building control systems (e.g. security).<ref>{{cite web|title=Lighting control saves money and makes sense|url=http://www.daintree.net/downloads/whitepapers/smart-lighting.pdf|publisher=[[Daintree Networks]]}}</ref>

In response to [[Daylighting (architecture)|daylighting]] technology, [[daylight harvesting]] systems have been developed to further reduce energy consumption. These technologies are helpful, but they do have their downfalls. Many times, rapid and frequent switching of the lights on and off can occur, particularly during unstable weather conditions or when daylight levels are changing around the switching illuminance. Not only does this disturb occupants, it can also reduce lamp life.  A variation of this technology is the 'differential switching or dead-band' photoelectric control which has multiple illuminances it switches from so as not to disturb occupants as much.<ref name="ReferenceA"/><ref>{{cite journal | last1 = Hung-Liang | first1 = C | last2 = Yung-Hsin | first2 = H | year = 2010 | title = Design and Implementation of Dimmable Electronic Ballast for Fluorescent Lamps Based on Power-Dependent Lamp Model | journal = IEEE Transactions on Plasma Science | volume = 38 | issue = 7| pages = 1644–1650 | doi=10.1109/tps.2010.2048928| bibcode = 2010ITPS...38.1644C | s2cid = 6094389 }}</ref>

Occupancy sensors to allow operation for whenever someone is within the area being scanned can control lighting. When motion can no longer be detected, the lights shut off. Passive infrared sensors react to changes in heat, such as the pattern created by a moving person. The control must have an unobstructed view of the building area being scanned.  Doors, partitions, stairways, etc. will block motion detection and reduce its effectiveness. The best applications for passive infrared occupancy sensors are open spaces with a clear view of the area being scanned. Ultrasonic sensors transmit sound above the range of human hearing and monitor the time it takes for the sound waves to return. A break in the pattern caused by any motion in the area triggers the control. Ultrasonic sensors can see around obstructions and are best for areas with cabinets and shelving, restrooms, and open areas requiring 360-degree coverage. Some occupancy sensors utilize both passive infrared and ultrasonic technology, but are usually more expensive. They can be used to control one lamp, one fixture or many fixtures.<ref>Hanselaer P, Lootens C, Ryckaert W, Deconinck G, Rombauts P. Power density targets for efficient lighting of interior task areas. [[Lighting Research & Technology]] [serial online]. June 2007;39(2):171-182. Available from: Academic Search Premier, Ipswich, MA.</ref><ref>Ryckaert W, Lootens C, Geldof J, Hanselaer P. Criteria for energy efficient lighting in buildings. Energy & Buildings [serial online]. March 2010;42(3):341-347. Available from: Academic Search Premier, Ipswich, MA.</ref>

===Daylighting===
{{main|Daylighting (architecture)}}

[[File:Gare de l'Est Paris 2007 033.jpg|thumb|Daylight used at the train station [[Gare de l'Est]] Paris]]
Daylighting is the oldest method of interior lighting.  Daylighting is simply designing a space to use as much natural light as possible. This decreases energy consumption and costs, and requires less heating and cooling from the building. Daylighting has also been proven to have positive effects on patients in hospitals as well as work and school performance. Due to a lack of information that indicate the likely energy savings, daylighting schemes are not yet popular among most buildings.<ref name="ReferenceA"/><ref name="ScienceWashington">Ulrich R S. View through a Windows May Influence Recovery from Surgery. Science (Washington D C) [serial online]. 1984;224(4647):420-421.</ref> Unlike electric lighting, the distribution of daylight varies considerably throughout the entire year inside a building.<ref>{{cite journal |last1=Kent |first1=Michael |last2=Schiavon |first2=Stefano |last3= Jakubiec |first3=Alstan |year=2020 |title=A dimensionality reduction method to select the most representative daylight illuminance distributions |journal=Journal of Building Performance Simulation |volume=13 |issue=1 |pages=122–135 |doi=10.1080/19401493.2019.1711456 |s2cid=211093664 |url=https://escholarship.org/uc/item/04x6v86j }}<!--|access-date=November 08, 2021--></ref>

===Solid-state lighting===
{{main|Solid-state lighting}}

In recent years [[light-emitting diode]]s (LEDs) are becoming increasingly efficient leading to an extraordinary increase in the use of [[Solid-state lighting|solid state lighting]]. In many situations, controlling the light emission of LEDs may be done most effectively by using the principles of [[nonimaging optics]].<ref name="IntroNio2e">{{cite book | first = Julio | last = Chaves | title = Introduction to Nonimaging Optics, Second Edition |url=https://books.google.com/books?id=e11ECgAAQBAJ | publisher = [[CRC Press]] |  year = 2015 | isbn = 978-1482206739}}</ref>

==Health effects==
{{main|Light pollution|Over-illumination|Light effects on circadian rhythm}}
{{see also|Ecological light pollution}}

It is valuable to provide the correct light intensity and color spectrum for each task or environment.  Otherwise, energy not only could be wasted but [[over-illumination]] can lead to adverse health and psychological effects. Beyond the energy factors being considered, it is important not to over-design illumination, lest adverse health effects such as [[headache]] frequency, stress, and increased [[blood pressure]] be induced by the higher lighting levels.  In addition, glare or excess light can decrease worker efficiency.<ref>{{Cite book
 | first = Craig
 | last = DiLouie
 | title = Advanced Lighting Controls: Energy Savings, Productivity, Technology and Applications
 | publisher = The Fairmont Press, Inc.
 | year = 2006
 | isbn = 978-0-88173-510-9
 }}</ref>

Analysis of lighting quality particularly emphasizes use of natural lighting, but also considers spectral content if artificial light is to be used. Not only will greater reliance on natural light reduce energy consumption, but will favorably impact human health and performance. New studies have shown that the performance of students is influenced by the time and duration of daylight in their regular schedules. [[Light in school buildings|Designing school facilities]] to incorporate the right types of light at the right time of day for the right duration may improve student performance and well-being. Similarly, designing lighting systems that maximize the right amount of light at the appropriate time of day [[Lighting for the elderly|for the elderly]] may help relieve symptoms of Alzheimer's disease.  The human circadian system is entrained to a 24-hour light-dark pattern that mimics the earth's natural light/dark pattern. When those patterns are disrupted, they disrupt the natural circadian cycle. [[Circadian rhythm#Human health|Circadian disruption]] may lead to numerous health problems including breast cancer, [[seasonal affective disorder]], [[delayed sleep phase syndrome]], and other ailments.<ref>{{cite journal | last1 = Figueiro | first1 = MG | last2 = Rea | first2 = MS | year = 2010 | title = Lack of short-wavelength light during the school day delays dim light melatonin onset (DLMO) in middle school students | journal = Neuro Endocrinology Letters | volume = 31 | issue = 1| pages = 92–6 | pmid = 20150866 | pmc = 3349218 }}</ref><ref>{{cite journal | last1 = Figueiro | first1 = MG | last2 = Rea | first2 = MS | last3 = Bullough | first3 = JD | year = 2006 | title = Does architectural lighting contribute to breast cancer?". | journal = Journal of Carcinogenesis | volume = 5 | issue = 1| page = 20 | doi = 10.1186/1477-3163-5-20 | pmid = 16901343 | pmc=1557490 | doi-access = free }}</ref>

A study conducted in 1972 and 1981, documented by Robert Ulrich, surveyed 23 surgical patients assigned to rooms looking out on a natural scene. The study concluded that patients assigned to rooms with windows allowing much natural light had shorter postoperative hospital stays, received fewer negative evaluative comments in nurses' notes, and took fewer potent analgesics than 23 matched patients in similar rooms with windows facing a brick wall. This study suggests that due to the nature of the scenery and daylight exposure was indeed healthier for patients as opposed to those exposed to little light from the brick wall. In addition to increased work performance, proper usage of windows and daylighting crosses the boundaries between pure aesthetics and overall health.<ref name="ScienceWashington" /><ref>Newsham G, Brand J, Donnelly C, Veitch J, Aries M, Charles K. Linking indoor environment conditions to job satisfaction: a field study. Building Research & Information [serial online]. March 2009;37(2):129-147.</ref>

Alison Jing Xu, assistant professor of management at the [[University of Toronto Scarborough]] and Aparna Labroo of [[Northwestern University]] conducted a series of studies analyzing the correlation between lighting and human emotion. The researchers asked participants to rate a number of things such as: the spiciness of chicken-wing sauce, the aggressiveness of a fictional character, how attractive someone was, their feelings about specific words, and the taste of two juices–all under different lighting conditions. In their study, they found that both positive and negative human emotions are felt more intensely in bright light. Professor Xu stated, "we found that on sunny days depression-prone people actually become more depressed." They also found that dim light makes people make more rational decisions and settle negotiations easier. In the dark, emotions are slightly suppressed. However, emotions are intensified in the bright light.<ref name=Mientka-decisions>{{cite news|last=Mientka|first=Matthew|title=Ambient Lighting Affects Decision Making, Emotional Intensity|url=http://www.medicaldaily.com/ambient-lighting-affects-decision-making-emotional-intensity-269967|access-date=25 February 2014|newspaper=Medical Daily|date=25 February 2014}}</ref><ref name=Ellis-decisions>{{cite news|last=Ellis|first=Marie|title=Room lighting affects decision making, study suggests|url=http://www.medicalnewstoday.com/articles/273064.php|access-date=25 February 2014|newspaper=Medical News Today|date=25 February 2014}}</ref><ref name=Wood-decision>{{cite news|last=Wood|first=Janice|title=Got an Important Decision to Make? Dim the Lights|url=http://psychcentral.com/news/2014/02/23/got-an-important-decision-to-make-dim-the-lights/66258.html|access-date=25 February 2014|newspaper=Psych Central News|date=25 February 2014}}</ref>

==Environmental issues==

===Compact fluorescent lamps===
[[Compact fluorescent lamp]]s (CFLs) use less power than an [[incandescent lamp]] to supply the same amount of light, however they contain [[mercury (element)|mercury]] which is a disposal hazard. Due to the ability to reduce electricity consumption, many organizations encouraged the adoption of CFLs. Some electric utilities and local governments subsidized CFLs or provided them free to customers as a means of reducing electricity demand. For a given light output, CFLs use between one fifth and one quarter the power of an equivalent incandescent lamp. Unlike incandescent lamps CFLs need a little time to warm up and reach full [[brightness]]. Not all CFLs are suitable for dimming. CFL's have largely been replaced with LED technologies.

===LED lamps===
LED lamps provide significant energy savings over incandescent and fluorescent lamps.<ref>{{cite magazine |last=Gumbel|first=Peter|date=December 4, 2008|title=Lighting: Bright Idea|url=http://www.time.com/time/magazine/article/0,9171,1864316,00.html |magazine=Time |url-status=dead |archive-url=https://web.archive.org/web/20081214002145/http://www.time.com/time/magazine/article/0,9171,1864316,00.html |archive-date=14 December 2008}}</ref> According to the Energy Saving Trust, LED lamps use only 10% power compared to a standard incandescent bulb, where compact fluorescent lamps use 20% and energy saving halogen lamps 70%. The lifetime is also much longer&nbsp;— up to 50,000 hours. The downside when they were first popularized was the initial cost. By 2018, production costs dropped, performance increased, and energy consumption was reduced. While the initially cost of LEDs is still higher than incandescent lamps, the savings are so dramatic that there are very few instances that LEDs are not the most economical choice.

Scattered light from outdoor illumination may have effects on the environment and human health.<ref name=SciAmNewMap>{{cite magazine |url=http://www.scientificamerican.com/article/new-map-shows-the-dark-side-of-artificial-light-at-night/ |title=New Map Shows the Dark Side of Artificial Light at Night |first=Lee |last=Billings |date=June 10, 2016 |magazine=Scientific American |access-date=June 20, 2016}}</ref> For instance, one study conducted by the American Medical Association<ref>{{Cite web|url=http://www.ama-assn.org/ama/pub/news/news/2016/2016-06-14-community-guidance-street-lighting.page?|title=AMA Adopts Community Guidance to Reduce the Harmful Human and Environmental Effects of High Intensity Street Lighting|website=ama-assn.org|access-date=2016-06-20}}</ref> warned on the use of high blue content white LEDs in street lighting, due to their higher impact on human health and environment, compared to low blue content light sources (e.g. High Pressure Sodium, phosphor-coated or PC amber LEDs, and low CCT LEDs).

===Light pollution===
{{Main|Light pollution}}

[[Light pollution]] is a growing problem in reaction to excess light being given off by numerous signs, houses, and buildings. Polluting light is often wasted light involving unnecessary energy costs and carbon dioxide emissions. Light pollution is described as artificial light that is excessive or intrudes where it is not wanted. Well-designed lighting sends light only where it is needed without scattering it elsewhere. Poorly designed lighting can also compromise safety. For example, glare creates safety issues around buildings by causing very sharp shadows, temporarily blinding passersby making them vulnerable to would-be assailants.<ref>Claudio L. Switch On the Night. Environmental Health Perspectives [serial online]. January 2009;117(1):A28-A31. Available from: Academic Search Premier, Ipswich, MA.</ref><ref>Lynn A. See the Light. Parks & Recreation [serial online]. October 2010;45(10):81-82. Available from: Academic Search Premier, Ipswich, MA.</ref> The negative ecological effects of artificial light have been increasingly well documented.<ref>{{Cite journal|last1=Longcore|first1=Travis|last2=Rich|first2=Catherine|date=2004|title=Ecological light pollution|journal=Frontiers in Ecology and the Environment|language=en|volume=2|issue=4|pages=191–198|doi=10.1890/1540-9295(2004)002[0191:ELP]2.0.CO;2|issn=1540-9309|doi-access=}}</ref><ref>{{Cite journal|last1=Sanders|first1=Dirk|last2=Frago|first2=Enric|last3=Kehoe|first3=Rachel|last4=Patterson|first4=Christophe|last5=Gaston|first5=Kevin J.|date=January 2021|title=A meta-analysis of biological impacts of artificial light at night|url=https://www.nature.com/articles/s41559-020-01322-x|journal=Nature Ecology & Evolution|language=en|volume=5|issue=1|pages=74–81|doi=10.1038/s41559-020-01322-x|pmid=33139919|hdl=10871/123068 |s2cid=226243935|issn=2397-334X|hdl-access=free}}</ref> The World Health Organization in 2007<ref>{{cite journal |journal=Environ. Health Perspect. |year=2009 |issue=1 |volume=117 |pages=A20–A27 |pmc=2627884 |title=Missing the Dark: Health Effects of Light Pollution |first=Ron |last=Chepesiuk |pmid=19165374 |doi=10.1289/ehp.117-a20}}</ref> issued a report that noted the effects of bright light on flora and fauna, sea turtle hatchlings, frogs during mating season and the migratory patterns of birds. The American Medical Association in 2012<ref>{{cite web |website=Sky & Telescope |title=AMA Addresses Light Pollution |first=Camille M. |last=Carlisle |date=July 16, 2012 |url=http://www.skyandtelescope.com/astronomy-news/ama-addresses-light-pollution/ |access-date=June 20, 2016}}</ref> issued a warning that extended exposure to light at night increases the risk of some cancers.<ref name=SciAmNewMap/> Two studies in Israel from 2008 have yielded some additional findings about a possible correlation between artificial light at night and certain cancers.<ref>{{cite journal |journal=Chronobiology International: The Journal of Biological and Medical Rhythm Research |volume=25 |issue=1 |year=2008 |title=Light at night co-distributes with incident breast but not lung cancer in the female population of Israel |doi=10.1080/07420520801921572 |pmid = 18293150|first1=Itai |last1=Kloog |first2=Abraham |last2=Haim |first3=Richard G. |last3=Stevens |first4=Micha |last4=Barchana |first5=Boris A. |last5=Portnov |pages=65–81|s2cid=17334188 }}</ref>

====Effects on animals====
{{unsourced section|date=September 2024}}
{{seemain|Ecological light pollution}}
[[File:Moth near lamp (cropped).jpg|thumb|Moths circling an electric lightbulb]]
Artificial light at night refers to any light source other than a natural light source. Sources of artificial light include LEDS and fluorescents. This particular light source has effect on the reproduction, immune function, metabolism, thermoregulation and body temperature of organisms that need light for their daily activity.     

Firstly, most organisms metabolism largely depends on light. In some instances the presence of intense light starts up or increases enzyme activity inside the body of an animal. For diurnal organisms, high rate of metabolism takes place during the day and reduces or comes to a stop during the night thus, artificial light at night has a negative impact of the metabolism of diurnal organisms. Moreover, the body temperature of diurnal animals fall during the night but the presence of artificial light at night, then causes an increase in body temperature which affects the melatonin levels of the animal.       

Furthermore, for organisms such as birds, their sex organs are activated in relation to light intensity in certain periods during the summer at day time to aid reproduction. These sex organs are deactivated during the night but the presence of artificial light during the night sometimes disrupts their reproduction process.

==Professional organizations==

===International===
The [[International Commission on Illumination]] (CIE) is an international authority and standard defining organization on [[color]] and lighting. Publishing widely used standard metrics such as various CIE [[color space]]s and the [[color rendering index]].

The [[Illuminating Engineering Society]] (IES), in conjunction with organizations like [[American National Standards Institute|ANSI]] and [[ASHRAE]], publishes guidelines, standards, and handbooks that allow categorization of the illumination needs of different built environments. Manufacturers of lighting equipment publish photometric data for their products, which defines the distribution of light released by a specific luminaire. This data is typically expressed in standardized form defined by the IESNA.

The [[International Association of Lighting Designers]] (IALD) is an organization which focuses on the advancement of lighting design education and the recognition of independent professional lighting designers. Those fully independent designers who meet the requirements for professional membership in the association typically append the abbreviation IALD to their name.

The [[Professional Lighting Designers Association]] (PLDA), formerly known as ELDA is an organisation focusing on the promotion of the profession of Architectural Lighting Design. They publish a monthly newsletter and organise different events throughout the world.

The National Council on Qualifications for the Lighting Professions (NCQLP) offers the Lighting Certification Examination which tests rudimentary lighting design principles.  Individuals who pass this exam become "Lighting Certified" and may append the abbreviation LC to their name. This certification process is one of three national (U.S.) examinations (the others are CLEP and CLMC) in the lighting industry and is open not only to designers, but to lighting equipment manufacturers, electric utility employees, etc.

The Professional Lighting And Sound Association ([[PLASA]]) is a UK-based trade organisation representing the 500+ individual and corporate members drawn from the technical services sector. Its members include manufacturers and distributors of stage and entertainment lighting, sound, rigging and similar products and services, and affiliated professionals in the area. They lobby for and represent the interests of the industry at various levels, interacting with government and regulating bodies and presenting the case for the entertainment industry. Example subjects of this representation include the ongoing review of radio frequencies (which may or may not affect the radio bands in which wireless microphones and other devices use) and engaging with the issues surrounding the introduction of the RoHS ([[Restriction of Hazardous Substances Directive]]) regulations.

===National===
* [[Association de Concepteurs Eclairage]] (ACE) in [[France]]
* American Lighting Association (ALA) in the United States
* [[Associazione Professionisti dell'Illuminazione]] (APIL) in [[Italy]]
* [[Hellenic Illumination Committee]] (HIC) in [[Greece]]
* Indian Society of Lighting Engineers (ISLE)
* Institution of Lighting Engineers (ILE) in the [[United Kingdom]]
* [[Schweizerische Licht Gesellschaft]] (SLG) in [[Switzerland]]
* Society of Light and Lighting (SLL), part of the [[Chartered Institution of Building Services Engineers]] in the United Kingdom.<ref>{{cite web |url=https://www.cibse.org/society-of-light-and-lighting-sll |title=Society of Light and Lighting |publisher=Chartered Institution of Building Services Engineers |website=cibse.org}}</ref>
* [[United Scenic Artists]] Local 829 (USA829), membership for lighting designers as a category, with scenic designers, projection designers, costume designers, and sound designers, in the United States

==See also==
{{div col|colwidth=25em}}
* [[3D computer graphics]]
* [[Anglepoise lamp]], successful and innovative desk lamp design
* [[Automotive lighting]]
* [[Banning of incandescent light bulbs]]
* [[Bug zapper]]
* [[Candlepower]]
* [[Computer graphics lighting]]
* [[Fishing light attractor]], underwater lights to attract fish
* [[Home automation]]
* [[Light fixture]]
* [[Light in school buildings]]
* [[Light pollution]]
* [[Lighting control system]]s, for a buildings or residences
* [[Lighting for the elderly]]
* [[List of lighting design applications|List of Lighting Design Software]]
* [[Luminous efficacy]]
* [[Neon lighting]] (for signage)
* [[Over-illumination]]
* [[Seasonal affective disorder]]
* [[Sustainable lighting]]
* [[Three-point lighting]], technique used in both still photography and in film
{{div col end}}

===Inventors===
* [[Joseph Swan]], carbonized-thread filament incandescent lamp
* [[Alexander Nikolayevich Lodygin]], carbon-rod filament incandescent lamp
* [[Thomas Edison]], long-lasting incandescent lamp with high-resistance filament
* [[John Richardson Wigham]], lighthouse engineer

===Lists===
* [[List of environmental health hazards]]
* [[List of light sources]]
* [[Timeline of lighting technology]]

==References==
{{Reflist}}

{{Refbegin}}
* {{cite book
 | first = Jack L.
 | last = Lindsey
 | title = Applied Illumination Engineering
 | publisher = The Fairmont Press, Inc.
 | location = Lilburn, Georgia
 | year = 1991
 | isbn = 978-0-88173-060-9
}}
* {{cite book
 | first = John L.
 | last = Fetters
 | title = The Handbook of Lighting Surveys & Audits
 | publisher = CRC Press
 | year = 1997
 | isbn = 978-0-8493-9972-5
}}
* {{Cite journal
 | last1 = Guo
 | first1= Xin
 | last2 = Houser
 | first2= Kevin W.
 | year = 2004
 | title = A review of colour rendering indices and their application to commercial light sources
 | journal = Lighting Research and Technology
 | volume = 36
 | issue = 3
 | pages = 183–199
 | doi = 10.1191/1365782804li112oa
 | s2cid= 109227871
 }}

{{Refend}}

==External links==
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{{EB1922 Poster|Illuminating Engineering}}
* {{commons category-inline}}
* {{Wiktionary-inline}}
* [http://www.ies.org/ Illuminating Engineering Society of North America] – official website
* {{cite web |url=https://www.lightingassociates.org/i/u/2127806/f/tech_sheets/advanced_lighting_guidelines_2001.pdf |archive-url=https://web.archive.org/web/20211207110300/https://www.lightingassociates.org/i/u/2127806/f/tech_sheets/advanced_lighting_guidelines_2001.pdf |url-status=usurped |archive-date=December 7, 2021 |title=Advanced Lighting Guidelines |date=2001 |publisher= New Buildings Institute, Inc. |website=lightingassociates.org}}
* [https://www.lrc.rpi.edu/ Lighting Research Center at Rensselaer Polytechnic Institute]
* [http://lightingresearch.group.shef.ac.uk/index.html Lighting Research at the University of Sheffield]
* [http://lrt.sagepub.com/ Lighting Research and Technology; an international peered reviewed journal]
* {{cite web |url=https://www.cibse.org/society-of-light-and-lighting-sll |title=Society of Light and Lighting |publisher=Chartered Institution of Building Services Engineers |website=cibse.org}}

{{Artificial light sources}}
{{Room}}
{{Color topics}}

{{Authority control}}

[[Category:Lighting| ]]
[[Category:Architectural elements]]
[[Category:Garden features]]