Lighting or illumination is the deliberate use of
light to achieve practical or aesthetic effects. Lighting includes the use of both artificial
light sources like lamps and light fixtures, as well as natural illumination by capturing
daylight
Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation, and (often) both of these reflected by Earth and terrestrial objects, like landforms and buildings. Sunligh ...
.
Daylighting
Daylighting is the practice of placing windows, skylights, other openings, and Reflective surfaces (climate engineering), reflective surfaces so that sunlight (direct or indirect) can provide effective internal lighting. Particular attention is ...
(using windows, skylights, or 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 fixtures, and is a key part of
interior design. Lighting can also be an intrinsic component of
landscape projects.
History
With the
discovery of fire, the earliest form of artificial lighting used to illuminate an area were
campfires or
torches. As early as 400,000 years ago, fire was kindled in the caves of
Peking Man.
Prehistoric
Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of ...
people used primitive
oil lamps to illuminate surroundings. These lamps were made from naturally occurring materials such as rocks, shells, horns and stones, were filled with
grease, and had a
fiber 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.
Fireflies have been used as lighting sources.
Candles and glass and pottery lamps were also invented.
Chandelier
A chandelier (; also known as girandole, candelabra lamp, or least commonly suspended lights) is a branched ornamental light fixture designed to be mounted on ceilings or walls. Chandeliers are often ornate, and normally use incandescent li ...
s were an early form of "
light fixture".
A major reduction in the cost of lighting occurred with the discovery of
whale oil.
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.
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.
By 1860, there were 33 kerosene plants in the United States, and Americans spent more on gas and kerosene than on whale oil.
The final death knell for whale oil was in 1859, when
crude oil
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crude ...
was discovered and the
petroleum industry arose.
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
electric lighting
An electric light, lamp, or light bulb is an electrical component that produces light. It is the most common form of artificial lighting. Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the soc ...
in the form of
arc lights for large space and
street lighting, followed by
incandescent light bulb-based utilities for indoor and outdoor lighting.
Over time, electric lighting became ubiquitous in developed countries.
Segmented sleep
Biphasic sleep (or ''diphasic'', ''bifurcated'', or bimodal sleep) is the practice of sleeping during two periods over the course of 24 hours, while polyphasic sleep refers to sleeping multiple times—usually more than two. Each of these is in ...
patterns disappeared, improved nighttime lighting made more activities possible at night, and more
street lights reduced urban crime.
Fixtures
Lighting fixture
A light fixture (US English), light fitting (UK English), or luminaire is an electrical device containing an Lamp (electrical component), electric lamp that provides Lighting, illumination. All light fixtures have a fixture body and one or more ...
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
Glare is difficulty of seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Because of this, some cars include mirrors with automatic anti-glare functions and in buildings ...
. 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 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
transparent the lighting fixtures are, the higher efficacy.
Shading the light will normally decrease efficacy but increase the directionality and the
visual comfort probability Visual comfort probability (VCP), also known as Guth Visual Comfort Probability, is a metric used to rate lighting
Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use o ...
.
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
kelvins of a theoretical
black body emitter that most closely matches the spectral characteristics 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.
Types
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 or
inspection
An inspection is, most generally, an organized examination or formal evaluation exercise. In engineering activities inspection involves the measurements, tests, and gauges applied to certain characteristics in regard to an object or activity. ...
of materials. For example, reading poor-quality reproductions may require task lighting levels up to 1500
lux
The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI). It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the ...
(150
footcandles), and some inspection tasks or
surgical procedures require even higher levels.
*
Accent lighting is mainly decorative, intended to highlight
picture
An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensiona ...
s,
plants, or other elements of
interior design or
landscaping.
* 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 on a table or floor, or a fixture on the
ceiling
A ceiling is an overhead interior surface that covers the upper limits of a room. It is not generally considered a structural element, but a finished surface concealing the underside of the roof structure or the floor of a story above. Ceilings ...
. Outdoors, general lighting for a
parking lot
A parking lot (American English) or car park (British English), also known as a car lot, is a cleared area intended for parking vehicles. The term usually refers to an area dedicated only for parking, with a durable or semi-durable surface ...
may be as low as 10-20 lux (1-2 footcandles) since
pedestrian
A pedestrian is a person traveling on foot, whether walking or running. In modern times, the term usually refers to someone walking on a road or pavement, but this was not the case historically.
The meaning of pedestrian is displayed with ...
s and
motorists already used to the dark will need little light for crossing the area.
Methods
*
Downlighting 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.
The introduction of
LED lighting
An LED lamp or LED light bulb is an electric light that produces light using light-emitting diodes (LEDs). LED lamps are significantly more energy-efficient than equivalent incandescent lamps
and can be significantly more efficient than mos ...
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.
*
Uplighting 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.
* 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
Glare (derived from GLAss REinforced laminate ) is a fiber metal laminate (FML) composed of several very thin layers of metal (usually aluminum) interspersed with layers of S-2 glass-fiber ''pre-preg'', bonded together with a matrix such as epo ...
near
eye
Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...
level.
*
Backlighting 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
Forms of lighting include
alcove lighting, which like most other uplighting is indirect. This is often done with
fluorescent lighting (first available at the
1939 World's Fair
The 1939–40 New York World's Fair was a world's fair held at Flushing Meadows–Corona Park in Queens, New York, United States. It was the second-most expensive American world's fair of all time, exceeded only by St. Louis's Louisiana Purcha ...
) or
rope light
A rope light is primarily used as a decorative lighting fixture, featuring small light bulbs linked together and encased in a PVC jacket to create a string of lights. Rope lights can be used in many applications both indoors and outdoors. Used in ...
, occasionally with
neon lighting, and recently with
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
Stucco or render is a construction material made of aggregates, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and a ...
or
plaster) on a wall, though this may also show its
defects as well. The effect depends heavily on the exact type of lighting source used.
Recessed lighting
A recessed light or downlight (also pot light in Canadian English, sometimes can light (for canister light) in American English) is a light fixture that is installed into a hollow opening in a ceiling. When installed it appears to have light s ...
(often called "pot lights" in
Canada, "can lights" or 'high hats" in the
US) is popular, with fixtures mounted into the ceiling structure so as to appear flush with it. These downlights can use narrow beam spotlights, or wider-
angle floodlights, both of which are bulbs having their own
reflector
Reflector may refer to:
Science
* Reflector, a device that causes reflection (for example, a mirror or a retroreflector)
* Reflector (photography), used to control lighting contrast
* Reflecting telescope
* Reflector (antenna), the part of an ant ...
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,
HID (high intensity discharge) or
LED
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
.
Track lighting, invented by
Lightolier, 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
Track lighting is a method of lighting where light fixtures are attached anywhere on a continuous track device which contains electrical conductors.https://books.google.com/books?id=bAEAAAAAMBAJ&pg=PA75&dq=%22track+lighting%22&hl=en&redir_esc=y#v ...
, where lights are hung from or clipped to bare
metal cables
Cable may refer to:
Mechanical
* Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof
* Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...
under
tension.
A
sconce
Sconce may refer to:
*Sconce (fortification), a military fortification
*Sconce (light fixture)
*Sconcing, imposing a penalty in the form of drink
*Sconce Point
Fort Victoria is a former military fort on the Isle of Wight, England (), built to ...
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
The portable or table lamp is probably the most common fixture, found in many homes and
offices. The standard lamp and shade that sits on a table is general lighting, while the desk lamp is considered task lighting.
Magnifier lamps are also task lighting.
The
illuminated ceiling was once popular in the 1960s and 1970s but fell out of favor after the 1980s. This uses
diffuser panels hung like a
suspended ceiling
A dropped ceiling is a secondary ceiling, hung below the main (structural) ceiling. It may also be referred to as a drop ceiling, T-bar ceiling, false ceiling, suspended ceiling, grid ceiling, drop in ceiling, drop out ceiling, or ceiling tile ...
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
A movie theater (American English), cinema (British English), or cinema hall ( Indian English), also known as a movie house, picture house, the movies, the pictures, picture theater, the silver screen, the big screen, or simply theater is a ...
, 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.
Outdoor lighting
Street Lights are used to light roadways and walkways at night. Some manufacturers are designing LED and photovoltaic luminaires to provide an energy-efficient alternative to traditional street light fixtures.
Floodlights can be used to illuminate work zones or outdoor playing fields during nighttime hours. The most common type of floodlights are metal halide and high pressure sodium lights.
Beacon lights are positioned at the intersection of two roads to aid in navigation.
Sometimes
security lighting In the field of physical security, security lighting is lighting that intended to deter or detect intrusions or other criminal activity occurring on a property or site. It can also be used to increase a feeling of safety. Lighting is integral to cri ...
can be used along roadways in urban areas, or behind homes or commercial facilities. These are extremely bright lights used to deter crime. Security lights may include floodlights and be activated with
PIR
Pir or PIR may refer to:
Places
* Pir, Kerman, a village in Kerman Province, Iran
* Pir, Satu Mare, commune in Satu Mare County, Romania
Religion
* Pir (Alevism), one of the 12 ranks of Imam in Alevism
* Pir (Sufism), a Sufi teacher or spiritu ...
switches that detect moving heat sources in darkness.
Entry lights can be used outside to illuminate and signal the entrance to a property. These lights are installed for safety, security, and for decoration.
Underwater accent lighting is also used for koi ponds, fountains, swimming pools and the like.
Neon signs are most often used to attract attention rather than to illuminate.
Vehicle use
Vehicles typically include
headlamps 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. 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
electroluminescent technology to
backlight their cars'
speedometer
A speedometer or speed meter is a gauge that measures and displays the instantaneous speed of a vehicle. Now universally fitted to motor vehicles, they started to be available as options in the early 20th century, and as standard equipment f ...
s and other gauges or to draw attention to
logos or other decorative elements.
Lamps
Commonly called 'light bulbs',
lamps
Lamp, Lamps or LAMP may refer to:
Lighting
* Oil lamp, using an oil-based fuel source
* Kerosene lamp, using kerosene as a fuel
* Electric lamp, or light bulb, a replaceable component that produces light from electricity
* Light fixture, or ligh ...
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
watts, 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 W incandescent light bulb produces about the same amount of light as a 13 W
compact fluorescent lamp. Each of these technologies has a different
efficacy
Efficacy is the ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as ''effectiveness'', and it has often been used synonymously, although in pharmacology a pragmatic clinical trial#Efficacy versu ...
in converting electrical energy to
visible light. Visible light output is typically measured in
lumens. 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. 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.
Lamp types include:
*
Ballast: A ballast is an auxiliary piece of equipment designed to start and properly control the flow of
power to discharge light sources such as
fluorescent and
high intensity discharge (HID) lamps. Some lamps require the ballast to have thermal protection.
*
fluorescent light: A tube coated with
phosphor
A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or vi ...
containing low pressure
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
vapor that produces white light.
*
Halogen
The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group is ...
: Incandescent lamps containing halogen gases such as iodine or bromine, increasing the efficacy of the lamp versus a plain incandescent lamp.
*
Neon
Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...
: A low pressure gas contained within a glass tube; the color emitted depends on the gas.
*
Light-emitting diodes: Light-emitting diodes (LED) are solid state devices that emit light by dint of the movement of electrons in a
semiconductor material.
*
Compact fluorescent lamps: CFLs are designed to replace incandescent lamps in existing and new installations.
Design and architecture
Architectural lighting design
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 for mathematical modeling, which can allow an architect to quickly 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.
On stage and set
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. 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
Measurement of light or
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
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls withi ...
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
The square metre ( international spelling as used by the International Bureau of Weights and Measures) or square meter (American spelling) is the unit of area in the International System of Units (SI) with symbol m2. It is the area of a square w ...
(cd/m
2). The
CGS unit of luminance is the
stilb, which is equal to one candela per square centimetre or 10 kcd/m
2. The amount of useful light emitted from a source or the
luminous flux
In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of electromagnetic radiation (including infrared, ultraviolet, and visible light), in th ...
is measured in
lumen (lm).
The
SI unit of
illuminance and
luminous emittance, being the luminous power per area, is measured in
Lux
The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI). It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the ...
. It is used in
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
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.
Visual comfort often entails the measurement of subjective evaluations. Several measurement methods have been developed to control glare resulting from indoor lighting design. The
Unified Glare Rating
Glare is difficulty of seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Because of this, some cars include mirrors with automatic anti-glare functions and in building ...
(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.
Color properties
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 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.
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. 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
An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the de ...
. The Daysimeter can gather data for up to 30 days for analysis.
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
fixtures and lamps that reflect best available technology for
energy conservation
Energy conservation is the effort to reduce wasteful energy consumption by using fewer energy services. This can be done by using energy more effectively (using less energy for continuous service) or changing one's behavior to use less service (f ...
* 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
Liter of Light is an open source design for a low-cost light tube that refracts solar light to provide daytime interior lighting for dwellings with thin roofs. Daylighting is cheaper than using indoor electric lights during the day. The device i ...
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.
*
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
The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI). It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the ...
might be chosen for a work environment involving meeting rooms and conferences, whereas a level of 80 lux could be selected for building hallways. If the hallway standard simply emulates the conference room needs, then much more energy will be consumed than is needed.
Lighting control systems
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
Demand response is a change in the power consumption of an electric utility customer to better match the demand for power with the supply. Until the 21st century decrease in the cost of pumped storage and batteries electric energy could not be ...
and will automatically dim or turn off lights to take advantage of
utility incentives. Lighting control systems are sometimes incorporated into larger
building automation systems.
Many newer control systems are using
wireless mesh open standards (such as
ZigBee), which provides benefits including easier installation (no need to run control wires) and interoperability with other standards-based building control systems (e.g. security).
In response to
daylighting
Daylighting is the practice of placing windows, skylights, other openings, and Reflective surfaces (climate engineering), reflective surfaces so that sunlight (direct or indirect) can provide effective internal lighting. Particular attention is ...
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.
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.
Daylighting
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.
[Ulrich R S. View through a Windows May Influence Recovery from Surgery. Science (Washington D C) erial online 1984;224(4647):420-421.] Unlike electric lighting, the distribution of daylight varies considerably throughout the entire year inside a building.
Solid-state lighting
In recent years
light-emitting diodes (LEDs) are becoming increasingly efficient leading to an extraordinary increase in the use of
solid state lighting
Solid-state lighting (SSL) is a type of lighting that uses semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, pl ...
. In many situations, controlling the light emission of LEDs may be done most effectively by using the principles of
nonimaging optics.
Health effects
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
Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches.
Headaches can occur as a result ...
frequency, stress, and increased
blood pressure
Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...
be induced by the higher lighting levels. In addition, glare or excess light can decrease worker efficiency.
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.
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
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 disruption may lead to numerous health problems including breast cancer,
seasonal affective disorder,
delayed sleep phase syndrome, and other ailments.
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.
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.
Environmental issues
Compact fluorescent lamps
Compact fluorescent lamps (CFLs) use less power than an
incandescent lamp
An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxid ...
to supply the same amount of light, however they contain
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
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. 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 — 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 aren’t the most economical choice.
Scattered light from outdoor illumination may have effects on the environment and human health.
For instance, one study conducted by the American Medical Association 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).
While that data may have been suspect even prior to publication, there’s no question that the solid state technology that are LEDs, has evolved substantially since then and we no longer use the lamps that were available for study at that time.
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. The negative ecological effects of artificial light have been increasingly well documented. The World Health Organization in 2007 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 issued a warning that extended exposure to light at night increases the risk of some cancers.
[ Two studies in Israel from 2008 have yielded some additional findings about a possible correlation between artificial light at night and certain cancers.
]
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 spaces and the color rendering index.
The Illuminating Engineering Society (IES), in conjunction with organizations like 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
Association may refer to:
*Club (organization), an association of two or more people united by a common interest or goal
*Trade association, an organization founded and funded by businesses that operate in a specific industry
*Voluntary associatio ...
(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
). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...
* Society of Light and Lighting (SLL), part of the Chartered Institution of Building Services Engineers in the United Kingdom.
* 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
* 3D computer graphics
3D computer graphics, or “3D graphics,” sometimes called CGI, 3D-CGI or three-dimensional computer graphics are graphics that use a three-dimensional representation of geometric data (often Cartesian) that is stored in the computer for th ...
* Anglepoise lamp, successful and innovative desk lamp design
* Automotive lighting
The lighting system of a motor vehicle consists of lighting and signalling devices mounted to or integrated into the front, rear, sides, and in some cases the top of a motor vehicle. They illuminate the road ahead for the driver and increase t ...
* Banning of incandescent light bulbs
* Bug zapper
* Candlepower
* Computer graphics lighting
* Fishing light attractor, underwater lights to attract fish
* Home automation
Home automation or domotics is building automation for a home, called a smart home or smart house. A home automation system will monitor and/or control home attributes such as lighting, climate, entertainment systems, and appliances. It m ...
* Light fixture
* Light in school buildings Light in school buildings traditionally is from a combination of daylight and electric light to illuminate learning spaces (e.g. classrooms, labs, studios, etc.), hallways, cafeterias, offices and other interior areas. Light fixtures currently in us ...
* Light pollution
* Lighting control system
A lighting control system is an intelligent network based lighting control solution that incorporates communication between various system inputs and outputs related to lighting control with the use of one or more central computing devices. Light ...
s, for a buildings or residences
* Lighting for the elderly Designing lighting for the elderly requires special consideration and care from architects and lighting designers. As people age, they experience neurodegeneration in the retina and in the suprachiasmatic nucleus (SCN). Less light reaches the bac ...
* List of Lighting Design Software
* Luminous efficacy
* Neon lighting (for signage)
* Over-illumination
* Seasonal affective disorder
* Sustainable lighting
Sustainable lighting is lighting designed with energy efficient light sources. "There are simple design strategies and some materials that can facilitate the energy saving advantages of natural light. Light colored interiors and open floor plans ...
* Three-point lighting, technique used in both still photography and in film
Inventors
* Joseph Swan, carbonized-thread filament incandescent lamp
* Alexander Nikolayevich Lodygin
Alexander Nikolayevich Lodygin, known after immigration to US as Alexandre de Lodyguine (russian: Александр Николаевич Лодыгин; 18 October 1847 – 16 March 1923) was a Russian electrical engineer and inventor, one of ...
, carbon-rod filament incandescent lamp
* Thomas Edison, long-lasting incandescent lamp with high-resistance filament
* John Richardson Wigham
:''This article concerns the Irish-based inventor and lighthouse engineer, not his cousin the shipbuilder John Wigham Richardson''.
John Richardson Wigham (15 January 1829 – 16 November 1906) was a prominent lighthouse engineer of the 19th cen ...
, lighthouse engineer
Lists
* List of environmental health hazards
* List of light sources
* Timeline of lighting technology
Artificial lighting technology began to be developed tens of thousands of years ago and continues to be refined in the present day.
Antiquity
* 125,000 BC Widespread control of fire by early humans.
* 17,500 BC oldest documented lamp, utilizi ...
References
*
*
*
External links
*
*
Illuminating Engineering Society of North America
– official website
*
Lighting Research Center at Rensselaer Polytechnic Institute
Lighting Research and Technology; an international peered reviewed journal
*
{{Authority control
Architectural elements
Garden features