Lighting
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Wikipedia-Article "Lighting"
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.
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Lighting design
Lighting design as it applies to the built environment, also known as 'architectural lighting design', is both a science and an art. Proper 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 artificial light production and luminaire photometrics are balanced with the artistic application of light as a medium in our built environment. These artificial lighting systems should also consider the impacts of, and ideally be integrated with, daylighting systems.
Lighting design requires the consideration of several design factors:
- tasks occurring in the environment
- occupants of the environment
- initial and continued operational costs
- aesthetic architectural impact
- physical size of the environment
- surface characteristics (reflectance, specularity)
- dirt and dust generation/accumulation
- maintenance capabilities
- operating schedule of the building
- electrical codes and building codes
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.
Modeling
For very simple layouts in common 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 natural 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.
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.
Types
Lighting is classified by its 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 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.
Methods
Downlighting is most common, with fixtures on the ceiling casting light downward. This tends to be the most efficient method, used in both offices and homes.
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.
Forms
Particular forms 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 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.
Fixtures
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 three pin XLR cable, although,some older theatres still use five pin DMX cabling. Generally, standard sound XLR cabling is not suitable for lighting, because the gauge of the wire is too small.
Types of conventional theatrical fixtures
Conventional Fixtures are stationary or 'fixed' and normally controlled by a power cable, allowing the fixture to output a beam of light with a brightness of 0 to 100 percent. Power for the fixtures is provided by dimmers which receive control signal, either digitally multiplexed (DMX) or analog + / − 12v from the main lighting desk or console, where all of the lights used in a production are controlled. A short cable is normally hardwired or connected to the body of the light and has an electrical connector on the end. Connectors are fuseless, as the fuse for the fixture is provided at the dimmer end of the circuit.
Types of fixtures include:
- Profile spot (various beam angles)
- Fresnel (variable beam angle)
- Prism Convex (variable beam angle)
- Par (exchangeable bulbs create varying beam angles/effects)
- Flood (used primarily for lighting backdrops)
Although these fixtures are of the 'fixed' variety, they are adjustable to a huge degree.
Profiles
Used for front (face) lighting and, with the insertion of a 'gobo' (stainless steel pattern) are used for break-up effects or projecting simple images onto the stage floor or set/backdrop. Profiles have one or two convex or plano-convex lenses, which can be adjusted to create a larger or smaller beam, with a hard or soft edge, and have steel shutters placed at the focal point of these lenses, to cut away unwanted portions of the beam.
Fresnel
Used for colour washes, side, front and back-lighting. These have a pebbled lens with concentric rings, which results in a large hazy circle around the focal point of the lantern. The beam size is adjusted by a screw, which actually moves the bulb of the fixture forwards and backwards within the body of the lamp. Large metal 'barndoors' (four in total) are affixed to the front of the lamp on a rotating ring, to cut away unwanted parts of the beam.
Prism Convex (PC)
Prism Convex fixtures or 'PCs', are much the same as fresnels, but with a prism convex lens instead of fresnel lens. The body of PCs is longer than fresnels. Pcs produce a more focused beam than fresnels, and are suitable for many of the same applications as fresnels and profiles.
Par (or 'par can')
Pars or par cans are among the most simple and widely-used theatrical lighting fixtures. They basically consist of a tube of steel or aluminum with a rounded removeable end, for changing lamps (bulbs). Par lamps contain a reflector, filament and lens in an enclosed glass envelope, and have various beam types:
- Very Narrow Spot (VNS or CP60)
- Narrow Spot (NS or CP61)
- Medium Flood (M
- Wide Flood (W or CP62)
- Very wide
Flood
Floods usually have a halogen tube bulb, backed by a curved symmetric or asymmetric reflector, to give a flat beam to be used for lighting sets or backdrops from above or below.
Color Frames
All Theatrical Lighting Fixtures should have a steel or metal color or 'gel' frame, which slots into a receiver at the front of the fixture. These are used for holding acrylic color 'gel', which is available in many hundreds of shades and hues.
Lamps
Commonly referred to as 'light bulbs', lamps are the removable/replaceable portion of a luminaire which convert electrical energy to both visible and non-visible electromagnetic energy.
Incandescent lamps
The incandescent light bulb was the first type of bulb, and is inefficient at converting electricity to light. About 90% of the energy input is wasted as heat. This excess heat is then dumped into the air which, in warm climates, must then be cooled by ventilation or air conditioning, resulting in more energy wastage. Due to their heat output, incandescent bulbs can cause burns or start fires if used improperly, and tend to have greater glare.
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.
Fluorescent lamps
Fluorescent bulbs are about 40% efficient, meaning that for the same amount of light they use 1/4 the power and produce 1/6 the heat of a regular incandescent. Fluorescents were limited to linear and a few circular ones until the 1980s, when the compact fluorescent was invented. The compacts can plug into their own fixture, or fit in to a standard screw base for self-ballasted ones. All last far longer than incandescents, but do have some starting trouble in very cold weather when installed outside.
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.
HID lamps
High-intensity discharge lighting first came about with the mercury-vapor streetlights, and later the high-pressure sodium ones with their characteristic orange color. Modern ones are metal halide, used in everything from headlights to floodlights, and with a more pleasant color balance. Like fluorescents, all HID bulbs require a ballast, but they also require a few minutes (or seconds for headlights) to warm up after "igniting". HID bulbs are over 60% and up to 80% efficient.
LED lamps
LEDs are a very recent introduction to the market, and they are still extremely expensive for any decent-sized bulb. They do however last an extremely long time, up to 100,000 hours (compared to around 10,000 for fluorescent and 1,000 for incandescent). These have come about only since the white LEDs they use, and in turn the blue LEDs which they were based on. It appears that for now these will be most useful and cost-effective in smaller applications, starting with nightlights. Colored LEDs can also be used for accent lighting, even in fake ice cubes for drinks at parties. They are also being increasingly used for Christmas lights, and not just the battery-powered kind. White LEDs are about the same efficiency as other fluorescents, while red ones can be up to 90% efficient.
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.
Vehicle lighting
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. In the image to the right, the top (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, 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.
See also
- 3D computer graphics
- digital car lighting
- domotics: computer controlled home lighting.
- chandelier
- Green Light: underwater lights to attract fish