Lighting includes both artificial light sources such as lamps and natural illumination of interiors with daylight. Lighting represents a major component of energy consumption, accounting for a significant part of all energy consumed worldwide. Artificial lighting is most commonly provided today by electric lights. However, gas lighting, candles, and oil lamps were used in the past, and are still used in certain situations. Proper lighting can enhance task performance or aesthetics, whereas there can be energy wastage and adverse health effects of lighting. Indoor lighting is a form of fixture or furnishing, and a key part of interior design. Lighting can also be an intrinsic component of landscaping.
Lighting fixtures come in a wide variety of styles for various functions. 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 heat and is in keeping with safety codes.
Proper selection of fixtures is complicated by the requirement to minimize the veiling reflections off printed material. Since the exact orientation of printed material may not be closed controlled, a visual comfort probability can be calculated for a given set of lighting fixtures.
Lighting is classified by intended use as general, localized, 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 of materials. For example, reading poor-quality reproductions may require task lighting levels up to 1500 lux (150 footcandles), and some inspection tasks or surgical procedures require even higher levels.
- Accent lighting is mainly decorative, intended to highlight pictures, plants, or other elements of interior design or landscaping.
- General lighting 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. Outdoors, general lighting for a parking lot may be as low as 10-20 lux (1-2 footcandles) since pedestrians and motorists already used to the dark will need little light for crossing the area.
- 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.
- 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 principal.
- 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 near eye level. Backlighting either around or through an object is mainly for accent.
Forms of Lighting include alcove lighting, which like most other uplighting is indirect. This is often done with fluorescent lighting or rope light, or occasionally with neon 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 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 U.S.) 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 reflectors. 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, though only reflector incandescent or HID lamps are available in spot configuration.
Track lighting, invented by Lightolier, was popular at one point 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 cables under tension.
A sconce is a wall-mounted fixture, particularly one that shines up and sometimes down as well. A torchiere is an uplight intended for ambient lighting. It is typically a floor lamp but may be wall-mounted like a sconce.
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 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. Underwater accent lighting is also used for koi ponds, fountains, swimming pools and the like.
In a movie theater each step in the aisles is usually marked with a row of small lights, for convenience and safety when the film has started, hence 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.
Vehicles typically include headlights and tail lights. Headlights are white or yellow lights placed in the front of the vehicle, designed to illuminate the upcoming road and to make the vehicle more visible. Tail lights are always red and are placed in the rear to quickly alert other drivers about the vehicle's direction of travel. The white portion of the tail light is the back-up lamp, which when lit, is used to 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.
In addition to lighting for useful purposes, and early 1970s, manufacturers would sometimes backlight their logos and or other translucent paneling. In the 1990s, a popular trend was to customize vehicles with neon lighting, especially underneath the body of a car. In the 2000s, neon lighting is increasingly yielding to digital vehicle lighting, in which bright LEDs are placed on the car and operated by a computer which can be customized and programmed to display a range of changing patterns and colors, a technology borrowed from Christmas lights.
Commonly called 'light bulbs', lamps are the removable and replaceable portion of a luminaire which converts electrical energy to both visible and non-visible electromagnetic energy. Specialists who work with lighting, carefully avoid energetic units for measuring of the light output of sources of light. For example, instead of watt per steradian, the special unit candela is used; 1 candela=(1/683) W/steradian. Common characteristics used to evaluate lamp quality include efficiency measured in lumens per watt, typical lamp life measured in hours, and Color Rendering Index on a scale of 0 to 100. Cost of replacement lamps is also an important factor in any design.
Lighting design as it applies to the built environment, also known as 'architectural lighting design', is both a science and an art. Comprehensive lighting design requires consideration of the amount of functional light provided, the energy consumed, as well as the aesthetic impact supplied by the lighting system. Some buildings, like surgical centers and sports facilities, are primarily concerned with providing the appropriate amount of light for the associated task. Some buildings, like warehouses and office buildings, are primarily concerned with saving money through the energy efficiency of the lighting system. Other buildings, like casinos and theatres, are primarily concerned with enhancing the appearance and emotional impact of architecture through lighting systems. Therefore, it is important that the sciences of light production and luminaire photometrics are balanced with the artistic application of light as a medium in our built environment. These electrical lighting systems should also consider the impacts of, and ideally be integrated with, daylighting systems. Factors involved in lighting design are essentially the same as those discussed above in energy conservation analysis.
Mathematical modeling is normally used for complex lighting design, whereas, for simple configurations, tables and simple hand calculations can be used. Based on the positions and mounting heights of the fixtures, and their photometric characteristics, the proposed lighting layout can be checked for uniformity and quantity of illumination. For larger projects or those with irregular floor plans, lighting design software can be used. Each fixture has its location entered, and the reflectance of walls, ceiling, and floors can be entered. The computer program will then produce a set of contour charts overlaid on the project floor plan, showing the light level to be expected at the working height. More advanced programs can include the effect of light from windows or skylights, allowing further optimization of the operating cost of the lighting installation.
The Zonal Cavity Method is used as a basis for both hand, tabulated, and computer calculations. This method uses the reflectance coefficients of room surfaces to model the contribution to useful illumination at the working level of the room due to light reflected from the walls and the ceiling. Simplified photometric values are usually given by fixture manufacturers for use in this method.
Computer modeling of outdoor flood lighting usually proceeds directly from photometric data. The total lighting power of a lamp is divided into small solid angular regions. Each region is extended to the surface which is to be lit and the area calculated, giving the light power per unit of area. Where multiple lamps are used to illuminate the same area, each one's contribution is summed. Again the tabulated light levels (in lux or foot-candles) can be presented as contour lines of constant lighting value, overlaid on the project plan drawing. Hand calculations might only be required at a few points, but computer calculations allow a better estimate of the uniformity and lighting level.
Practical lighting design must take into account the gradual decrease in light levels from each lamp owing to lamp aging, lamp burnout, and dirt accumulation on fixture and lamp surfaces. Empirically-established depreciation factors are listed in lighting design handbooks.
Luminance is a photometric 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 meter (cd/m2). The CGS unit of luminance is the stilb, which is equal to one candela per square centimeter or ten kcd/m2.
Artificial lighting consumes a significant part of all electrical energy consumed worldwide. In homes and offices from 20 to 50 percent of total energy consumed is due to lighting. Most importantly, for some buildings over 90 percent of lighting energy consumed can be an unnecessary expense through over-illumination. The cost of that lighting can be substantial. A single 100 W light bulb used just six hours a day can cost over $25 per year to use (.12/kWh). Thus lighting represents a critical component of energy use today, especially in large office buildings where there are many alternatives for energy utilization in lighting. There are several strategies available to minimize energy requirements in any building:
- Specification of illumination requirements for each given use area.
- Analysis of lighting quality to insure 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 fixture and lamp types that reflect best available technology for energy conservation.
- Training of building occupants to utilize lighting equipment in most efficient manner.
- Maintenance of lighting systems to minimize energy wastage.
- Use of natural light. Some big box stores are being built (Ca 2006 on) with numerous plastic bubble skylights, in many cases completely obviating the need for interior artificial lighting for many hours of the day.
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.
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 or bathroom compared to that needed for a word processing work station. Prior to 1970 (and too often even today), a lighting engineer would simply apply the same level of illumination design to all parts of the building without considering usage. Generally speaking, the energy expended is proportional to the design illumination level. For example, a lighting level of 80 footcandles might be chosen for a work environment involving meeting rooms and conferences, whereas a level of 40 footcandles could be selected for building hallways. If the hallway standard simply emulates the conference room needs, then twice the amount of energy will be consumed as is needed for hallways. Unfortunately, most of the lighting standards even today have been specified by industrial groups who manufacture and sell lighting, so that a historical commercial bias exists in designing most building lighting, especially for office and industrial settings. 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.
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.
Kerosene and Whale Oil Lamps
In 1849, Dr. Abraham Gesner, a Canadian geologist, devised a method where kerosene could be distilled from petroleum. Earlier coal-gas methods had been used for lighting since the 1820s, but they were expensive. Gesner's kerosene was cheap, easy to produce, could be burned in existing lamps, and did not produce an offensive odor as did most whale oil. It could be stored indefinitely, unlike whale oil, which would eventually spoil. The American petroleum boom began in the 1850s. By the end of the decade there were 30 kerosene plants operating in the United States. The cheaper, more efficient fuel began to drive whale oil out of the market. John D. Rockefeller was most responsible for the commercial success of kerosene. He set up a network of kerosene distilleries which would later become Standard Oil, thus completely abolishing the need for Whale Oil lamps.
Compact fluorescent lamps
Compact fluorescent lamps (aka 'CFLs') use less power to supply the same amount of light as an incandescent lamp. Due to the ability to reduce electric consumption, many organizations have undertaken measures to encourage the adoption of CFLs. Some electric utilities and local governments have subsidized CFLs or provided them free to customers as a means of reducing electric demand. For a given light output, CFLs use between one fifth and one quarter of the power of an equivalent incandescent lamp. However, CFLs contain minute amounts of mercury, a toxic substance. Disposal of CFLs needs to be done with care, according to local regulations.
- Alexander Nikolayevich Lodygin
- Electromagnetic spectrum
- John Richardson Wigham
- Joseph Swan
- Light-emitting diode
- Nikola Tesla
- Thomas Edison
- David Vernon (2007), Light bulbs—Don’t be Dim. Light up your Life! Retrieved August 25, 2008.
- Paul Hawken, Amory B. Lovins, and L. Hunter Lovins, Natural Capitalism: Creating the Next Industrial Revolution (Boston: Little, Brown and Co., 2000, ISBN 0316353000).
- Craig DiLouie, Advanced Lighting Controls: Energy Savings, Productivity, Technology and Applications (Lilburn, GA: Fairmont Press, 2006, ISBN 0881735108).
- James S. Robbins, How Capitalism Saved the Whales The Foundation for Economic Education. Retrieved August 25, 2008.
- DiLouie, Craig. 2006. Advanced Lighting Controls: Energy Savings, Productivity, Technology and Applications. Lilburn, GA: Fairmont Press. ISBN 0881735108
- Fetters, John L. 1998. The Handbook of Lighting Surveys & Audits. Boca Raton: CRC Press. ISBN 0849399726
- Lindsey, Jack L. 1991. Applied Illumination Engineering. Lilburn, GA: Fairmont Press. ISBN 0881730602
All links retrieved July 6, 2018.
- Illuminating Engineering Society
- Lighting Research Center Rensselaer Polytechnic Institute.
- Moving beyond indifferent lighting
|Sources of light / lighting:|
Natural/prehistoric light sources:
Combustion-based light sources:
Nuclear/direct chemical light sources:
Betalights/Trasers | Chemoluminescence (Lightsticks)
Electric light sources:
High-intensity discharge light sources:
Ceramic Discharge Metal Halide lamps | HMI lamps | Mercury-vapor lamps | Metal halide lamps | Sodium vapor lamps | Xenon arc lamps
Other electric light sources:
Electroluminescent (EL) lamps | Globar | Inductive lighting | Discrete LEDs/Solid State Lighting (LEDs) | Neon and argon lamps | Nernst lamp | Sulfur lamp | Xenon flash lamps | Yablochkov candles
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