ESSAY ON ILLUMINATION OR LIGHTING
illumination or lighting is playing a huge role in environment design in which the deliberate application of light to achieve some aesthetic or practical effect. Lighting includes use of both artificial light sources such as lamps and natural illumination of interiors from daylight. Day lighting (through windows, skylights, etc.) is often used as the main source of light during daytime in buildings given its low cost.
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, but gas lighting, candles, or oil lamps were used in the past, and still are used in certain situations. Proper lighting can enhance task performance or aesthetics, while there can be energy wastage and adverse health effects of poorly designed lighting. Indoor and outdoor lighting is a form of fixture or furnishing, and a key part of environmental design. Lighting can also be an intrinsic component of landscaping.
With the development of high efficiency and high power light-emitting diode (LED) it has become possible to incorporate LED in lighting and illumination. Replacement light bulbs have been made as well as dedicated fixtures and LED lamps. LED are used as street lights and in other architectural lighting where colour changing is used. The mechanical robustness and long lifetime is used in automotive lighting on cars, motorcycles and on bicycle lights.
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 foot-candles), 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 foot-candles) since pedestrians and motorists already used to the dark will need little light for crossing the area.
There are various method of lighting we can use today such as down lighting which 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.
Up lighting 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 luminance levels. Up lighting (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 up lighting 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.
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. Some 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 theatre 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.
Street Lights are used to light roadways and walkways at night. Some manufacturers are designing LED and photovoltaic luminaries to provide an energy-efficient alternative to traditional street light fixtures. Floodlights can be used to illuminate outdoor playing fields or work zones during nighttimes hours. The most common type of floodlights is metal halide and high pressure sodium lights. Beacon lights are positioned at the intersection of two roads to aid in navigation.
Security lights 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. 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.
Vehicle uses 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.
LED lamps have been advocated as the newest and best environmental lighting method. According to the Energy Saving Trust, LED lamps use only 10% power compared to a standard incandescent bulb, where fluorescent lamps use compact 20% and energy saving halogen lamps 70%.
Lamps are the removable and replaceable portion of a luminaries' 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 due to the spectral response of human visual perception.
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 centres 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 luminaries photometric 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 day lighting systems.
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. Thus lighting represents a critical component of energy use today, especially in large office buildings where there are many alternatives for energy usage in lighting.
It is valuable to provide the correct light intensity and colour 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.
Generally the energy expended is proportional to the design illumination level. For example, a lighting level of 80 foot-candles might be chosen for a work environment involving meeting rooms and conferences, whereas a level of 40 foot-candles 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. 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.
A building's carbon footprint from lighting can be reduced by 68% by exchanging all incandescent bulbs for new LEDs in warm climates. In cold climates, the energy saving may be lower, since more heating would be needed to compensate for the lower temperature.
LEDs are also non-toxic unlike the more popular energy efficient bulb such as the compact fluorescent which contains traces of harmful mercury
Light has many other uses besides for seeing. LEDs are used for some of these applications. The uses fall in three groups: Communication, sensors and light matter interaction.
The light from LEDs can be modulated very quickly so they are used extensively in optical fibre and Free Space Optics communications. This includes remote controls, such as for TVs and VCRs, where infrared LEDs are often used. Opto-isolators use an LED combined with a photodiode or phototransistor to provide a signal path with electrical isolation between two circuits. This is especially useful in medical equipment where the signals from a low voltage sensor circuit (usually battery powered) in contact with a living organism must be electrically isolated from any possible electrical failure in a recording or monitoring device operating at potentially dangerous voltages.
Many sensor systems rely on light as the signal source. LEDs are often ideal as a light source due to the requirements of the sensors. LEDs are used as movement sensors, for example in optical computer mice. The Nintendo Wii sensor bar uses infrared LEDs. Some flatbed scanners use arrays of RGB LEDs rather than the typical cold-cathode fluorescent lamp as the light source. Having independent control of three illuminated colours allows the scanner to calibrate itself for more accurate colour balance, and there is no need for warm-up, its sensors only need be monochromatic, since at any one point in time the page being scanned is only lit by a single colour of light. Since LEDs can also be used as photodiodes, they can be used for both photo emission and detection. This could be used in for example a touch-sensing screen that register reflected light from a finger or stylus.
Materials and biological systems are sensitive to, or dependent on light. Grow lights use LEDs to increase photosynthesis in plants and bacteria and viruses can be removed from water and other substances using UV LEDs for sterilization. Other uses are as UV curing devices for some ink and coating applications as well as LED printers.
The use of LEDs is particularly interesting to plant cultivators, mainly because it is more energy efficient, less heat is produced (can damage plants close to hot lamps) and can provide the optimum light frequency for plant growth and bloom periods compared to currently used grow lights.
Finally, it is worth pointing out that, the more light the better because we all need well lit main streets, security lights, and parking lot lighting. However, we do not need glare, clutter, confusion, light trespass, light pollution, and energy waste.
ASSIST recommends: Guide to Light and Colour in Retail Merchandising. 2010. Volume 8, Issue 1. Available online at: http://www.lrc.rpi.edu/programs/solidstate/assist/recommends/lightcolor.asp
Lindsey, Jack L. (1991). Applied Illumination Engineering. Lilburn, Georgia: The Fairmont Press, Inc.. ISBN0-88173-060-2
Fetters, John L (1997). The Handbook of Lighting Surveys & Audits. CRC Press. ISBN0-8493-9972-6.
Guo, Xin; Houser, Kevin W. (2004), "A review of colour rendering indices and their application to commercial light sources", Lighting Research and Technology 36 (3): 183-199, doi:10.1191/1365782804li112oa
Field Test DELTA: Post-Top Photovoltaic Pathway Luminaries. Iss. 4. Lighting Research Centre. Online at: http://www.lrc.rpi.edu/programs/DELTA/pdf/DELTA-Post-topPhotovoltaic.pdf [last accessed 18 April 2010]
Light bulbs Don't be Dim. Light up your Life!, David Vernon
LED advantages outweigh potential snow hazards in traffic signals, LEDs magazine 7 Jan 2010
ASSIST recommends: Guide to Light and Color in Retail Merchandising. 2010. Volume 8, Issue 1. Available online at: http://www.lrc.rpi.edu/programs/solidstate/assist/recommends/lightcolor.asp