Lighting refers to the devices or techniques used for illumination, usually referring to artificial light sources such as lamps or flashlights.
Natural indoor lighting is by windows and skylights.
Artificial indoor lighting is by means of lamps, today usually electric lights, but previously by gas, candles or oil lamps. Modern freestanding lamps typically have a Base which holds up a light bulb which is covered by a Lampshade. Modern portable lighting is typically a flashlight (also called a torch) running on batteries. Indoor lighting is a form of Furnishing, and a critical part of Interior design. Likewise, lighting can also be an important part of landscaping.
In cities, streets are often lighted at night, usually by streetlights (also known as lamp-posts). These are a form of Street furniture. Smaller or rural roads may not be lit. In major cities, Light pollution is of growing concern.
Lighting design requires the consideration of several design factors:
The Illuminating Engineering Society of North America (IESNA), 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 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 the only national examination in the lighting industry and is open not only to designers, but to lighting equipment manufacturers, electric utility employees, etc.
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.
Modelling of outdoor flood lighting usually proceeds directly from photometric data. The total lighting power of a lamp is divided into small soild 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) are 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.
Proper selection of fixtures is complicated by the requirement to minimize the veiling reflections off of 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.
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 illiumination 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 20 lux (2 footcandles) since pedestrians and motorists already used to the dark will need little light for crossing the area.
Uplighting is less common, often used to bounce indirect light off of the ceiling and back down, though this is less efficient than direct lighting. It can also be used for dramatic effect, such as creating interesting shadows by shining through Houseplant leaves or across coarse textures like Brick or Stone.
Lighting from the front is also quite common, but tends to make the subject look flat as its casts almost no shadows. Lighting from the side is the less common, as it tends to glare near Eye level. Backlighting either around or through an object is mainly for accent.
Soffit 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 used.
Recessed lighting (often called pot lights in Canada and can lights in the U.S.) is popular, with fixtures mounted above the ceiling so as to appear Flush with it. These downlights use narrow spotlights or "spots", or wider-Angle floodlights or "floods", which are both bulbs with their own reflectors. They may also have their own reflector built-in to the fixture, so that they can take regular and less-expensive bulbs. Either type can be incandescent, fluorescent, HID or LED, though only incandescents or LEDs make narrow-enough spots.
True can lights are uplights, sitting on the floor in a CAN-like fixture, or mounted on a spike or even in the ground for plants or outdoors.
Track lighting was popular at one point because it was much easier to install then 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 having its own. 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.
The LAMP is probably the most common fixture, found in every home and many 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 the 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 and the like.
Lighting fixtures come in a wide variety of styles for various functions. Some are very plain and fuctional, 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.
A Sconce is a wall-mounted fixture, particularly one that shines up and sometimes down as well.
A Torchiere (tour-she-AIR or tour-SHARE) is an uplight usually intended for general lighting. It is usually a floor lamp but may be wall-mounted like a sconce.
Concert and theatre lighting use special types of fixtures. Conventional lighting consists of stationary lights that can only be moved manually, by means of adjusting, or focusing the fixture with a yoke. Automated lighting fixtures use digital electronics to adjust the color, position, beam angle, brightness, and other special effects. In the United States, automated lighting fixtures are normally controlled by the United States Institute of Theatre Technology Digital Multiplex - 512 Channel Standard Protocol, or simply DMX-512. The protocol runs on standard five pin XLR cable.
Types of fixtures include:
Although these fixtures are of the 'fixed' variety, they are adjustable to a huge degree.
Halogen bulbs are an improved incandescent. Light energy output is about 15% of energy input, instead of 10%, allowing them to produce about 50% more light from the same amount of electrical power. The bulb Capsule is under high Pressure instead of a Vacuum or low-pressure Noble gas. As well as being much smaller and having a hotter Filament Temperature, this causes halogen bulbs to have a very hot surface. This means that Glass bulbs can explode if broken, or if operated with residue such as fingerprints on them. The risk of burns or fire is also greater than other bulbs, leading to their prohibition in some places. Halogen capsules can be put inside regular bulbs or dichroic reflectors, either for looks or for Safety.
Good halogen bulbs produce a sunshine-like white light, while regular incandescents produce a light between sunlight and Candlelight. People sometimes find them psychologically pleasing over other types of bulbs due to the more natural colour, which lights skin tones and other artifacts more accurately.
Fluorescents most often come in cool white (CW), with some home bulbs being a warm white (WW), which has a pinkish Tint. In between there is an "enhanced white" (EW), which is more Neutral. There is also a very cold daylight white (DW) which is rather unpleasant to most people and therefore rarely used. Compact ones are usually considered warm white, though many have a yellowish cast like an incandescent. Because the above terms are entirely relative and almost Arbitrary, Color temperature and/or the Color rendering index (CRI) are used as absolute scales of color for fluorescents, and sometimes for other types of lighting.
LED Technology for theatrical and concert applcations is still in its infancy, but is advancing at an incredible rate. Patent disputes of RGB colour mixing ideas are currently slowing development, despite the fact many products are being released that take advantage of red, green, blue, and sometimes white, LEDs to mix colours. LED technology is useful for lighting designers because of its low power consumption, low heat generation, instantaneous on/off control, continuity of colour throughout the life of the diode and relatively low cost of manufacture. In the last few years, software has been developed to merge lighting and video by enabling lighting designers to stream video content to their LED fixtures, creating low resolution video walls.
In addition to lighting for useful purposes, automobiles increasingly feature ornamental lighting. In the late 60s and early 70s, manufacturers would sometimes Backlight their logos and or other translucent panelling. In the 90s, 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 technlogy borrowed from Christmas lights.