This is an accepted version of this page
67-398: Electric light is an artificial light source powered by electricity. Electric Light may also refer to: Electric light 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 socket of
134-402: A grow light to aid in plant growth especially in indoor hydroponics and aquatic plants with recent research into the most effective types of light for plant growth. Due to their nonlinear resistance characteristics, tungsten filament lamps have long been used as fast-acting thermistors in electronic circuits. Popular uses have included: In Western culture, a lightbulb — in particular,
201-417: A light fixture , which is often called a "lamp" as well. The electrical connection to the socket may be made with a screw-thread base, two metal pins, two metal caps or a bayonet mount . The three main categories of electric lights are incandescent lamps, which produce light by a filament heated white-hot by electric current , gas-discharge lamps , which produce light by means of an electric arc through
268-581: A monochromatic orange-yellow light, which gives a similarly monochromatic perception of any illuminated scene. For this reason, it is generally reserved for outdoor public lighting applications. Low-pressure sodium lights are favoured for public lighting by astronomers, since the light pollution that they generate can be easily filtered, contrary to broadband or continuous spectra. Many lamp units, or light bulbs, are specified in standardized shape codes and socket names. Incandescent bulbs and their retrofit replacements are often specified as " A19 /A60 E26 /E27",
335-656: A motor-generator combo (AC motor powering a DC generator). Even in these applications conventional carbon-arc lamps were mostly pushed into obsolescence by xenon arc lamps , but were still being manufactured as spotlights at least as late as 1982 and are still manufactured for at least one purpose – simulating sunlight in "accelerated aging" machines intended to estimate how fast a material is likely to be degraded by environmental exposure. Carbon arc lighting left its imprint on other film projection practices. The practice of shipping and projecting motion pictures on 2,000-foot reels, and employing "changeovers" between two projectors,
402-506: A common size for those kinds of light bulbs. In this example, the "A" parameters describe the bulb size and shape within the A-series light bulb while the "E" parameters describe the Edison screw base size and thread characteristics. Common comparison parameters include: Less common parameters include color rendering index (CRI). Life expectancy for many types of lamp is defined as
469-414: A complete ban on incandescent bulbs would contribute 5 to 10 billion euros to the economy and save 15 billion metric tonnes of carbon dioxide emissions . Halogen lamps are usually much smaller than standard incandescent lamps, because for successful operation a bulb temperature over 200 °C is generally necessary. For this reason, most have a bulb of fused silica (quartz) or aluminosilicate glass. This
536-435: A gas, such as fluorescent lamps , and LED lamps , which produce light by a flow of electrons across a band gap in a semiconductor . The energy efficiency of electric lighting has increased radically since the first demonstration of arc lamps and the incandescent light bulb of the 19th century. Modern electric light sources come in a profusion of types and sizes adapted to many applications. Most modern electric lighting
603-422: A glass or silica envelope containing two metal electrodes separated by a gas. Gases used include, neon , argon , xenon , sodium , metal halides , and mercury . The core operating principle is much the same as the carbon arc lamp, but the term "arc lamp" normally refers to carbon arc lamps, with more modern types of gas discharge lamp normally called discharge lamps. With some discharge lamps, very high voltage
670-697: A number of people including William Edwards Staite [ de ] and Charles F. Brush . It was not until the 1870s that lamps such as the Yablochkov candle were more commonly seen. In 1877, the Franklin Institute conducted a comparative test of dynamo systems. The one developed by Brush performed best, and Brush immediately applied his improved dynamo to arc-lighting, an early application being Public Square in Cleveland, Ohio , on April 29, 1879. Despite this, Wabash, Indiana claims to be
737-401: A plasma state. However, the arc contributes very little of the light output, and is considered non-luminous, as most of its emission occurs in spectral lines in the violet and UV portions of the spectrum. Most of the carbon spectra occurs in a very broad line centered at 389 nm (UV-A, just outside the visual spectrum), and a very narrow line at 250 nm (UV-B), plus some other less-powerful lines in
SECTION 10
#1732787112972804-619: A renowned physicist and GE consultant, reported to the GE lamp department on successful experiments with fluorescent lighting at General Electric Co., Ltd. in Great Britain (unrelated to General Electric in the United States). Stimulated by this report, and with all of the key elements available, a team led by George E. Inman built a prototype fluorescent lamp in 1934 at General Electric 's Nela Park (Ohio) engineering laboratory. This
871-412: A sheet of ordinary window glass in front of the lamp, blocking the ultra-violet. By the dawn of the "talkies", arc lamps had been replaced in film studios with other types of lights. In 1915, Elmer Ambrose Sperry began manufacturing his invention of a high-intensity carbon arc searchlight . These were used aboard warships of all navies during the 20th century for signaling and illuminating enemies. In
938-475: A two-thousand- cell battery to create an arc across a 4-inch (100 mm) gap. He mounted his electrodes horizontally and noted that, because of the strong convection flow of air, the arc formed the shape of an arch. He coined the term "arch lamp", which was contracted to "arc lamp" when the devices came into common usage. In the late nineteenth century, electric arc lighting was in wide use for public lighting. The tendency of electric arcs to flicker and hiss
1005-905: Is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. Fluorescent lamp fixtures are more costly than incandescent lamps, because they require a ballast to regulate the current through the lamp, but the lower energy cost typically offsets the higher initial cost. Compact fluorescent lamps are available in the same popular sizes as incandescent lamps and are used as an energy-saving alternative in homes. Because they contain mercury, many fluorescent lamps are classified as hazardous waste . The United States Environmental Protection Agency recommends that fluorescent lamps be segregated from general waste for recycling or safe disposal, and some jurisdictions require recycling of them. The solid-state light-emitting diode (LED) has been popular as an indicator light in consumer electronics and professional audio gear since
1072-454: Is a similar principle where the atmosphere is ionized by the high potential difference (voltage) between earth and storm clouds. The temperature of the arc in an arc lamp can reach several thousand degrees Celsius. The outer glass envelope can reach 500 degrees Celsius, therefore before servicing one must ensure the bulb has cooled sufficiently to handle. Often, if these types of lamps are turned off or lose their power supply, one cannot restrike
1139-409: Is now obsolete for most of these purposes, but it is still used as a source of high intensity ultraviolet light. The term is now used for gas discharge lamps , which produce light by an arc between metal electrodes through a gas in a glass bulb. The common fluorescent lamp is a low-pressure mercury arc lamp. The xenon arc lamp , which produces a high intensity white light, is now used in many of
1206-465: Is often sealed inside an additional layer of glass. The outer glass is a safety precaution, to reduce ultraviolet emission and to contain hot glass shards should the inner envelope explode during operation. Oily residue from fingerprints may cause a hot quartz envelope to shatter due to excessive heat buildup at the contamination site. The risk of burns or fire is also greater with bare bulbs, leading to their prohibition in some places, unless enclosed by
1273-484: Is powered by centrally generated electric power, but lighting may also be powered by mobile or standby electric generators or battery systems. Battery -powered light is often reserved for when and where stationary lights fail, often in the form of flashlights or electric lanterns , as well as in vehicles. Before electric lighting became common in the early 20th century, people used candles , gas lights , oil lamps , and fires . In 1799–1800, Alessandro Volta created
1340-557: Is sufficient for cities to be easily visible at night from the air, and from space. External lighting grew at a rate of 3–6 percent for the later half of the 20th century and is the major source of light pollution that burdens astronomers and others with 80% of the world's population living in areas with night time light pollution. Light pollution has been shown to have a negative effect on some wildlife. Electric lamps can be used as heat sources, for example in incubators , as infrared lamps in fast food restaurants and toys such as
1407-407: Is the deciding factor, such as street lighting. More advanced electronic ballasts may be designed to maintain constant light output over the life of the lamp, may drive the lamp with a square wave to maintain completely flicker-free output, and shut down in the event of certain faults. The most efficient source of electric light is the low-pressure sodium lamp. It produces, for all practical purposes,
SECTION 20
#17327871129721474-559: Is the only lamp whose blackbody radiation is capable of nearly matching the Sun's temperature of 10,000 degrees Fahrenheit (5500 degrees Celsius), especially when filters are used to remove most of the IR and UV light. The concept of carbon-arc lighting was first demonstrated by Humphry Davy in the early 19th century, but sources disagree about the year he first demonstrated it; 1802, 1805, 1807 and 1809 are all mentioned. Davy used charcoal sticks and
1541-615: Is used to strike the arc. This requires an electrical circuit called an igniter, which is part of the electrical ballast circuitry. After the arc is struck, the internal resistance of the lamp drops to a low level, and the ballast limits the current to the operating current. Without a ballast, excess current would flow, causing rapid destruction of the lamp. Some lamp types contain a small amount of neon, which permits striking at normal running voltage with no external ignition circuitry. Low-pressure sodium lamps operate this way. The simplest ballasts are just an inductor, and are chosen where cost
1608-415: Is useful for lighting designers , because of its low power consumption, low heat generation, instantaneous on/off control, and in the case of single color LEDs, continuity of color throughout the life of the diode and relatively low cost of manufacture. LED lifetime depends strongly on the temperature of the diode. Operating an LED lamp in conditions that increase the internal temperature can greatly shorten
1675-528: The Thomson-Houston Electric Company . Thomson remained, though, the principal inventive genius behind the company patenting improvements to the lighting system. Under the leadership of Thomson-Houston's patent attorney, Frederick P. Fish , the company protected its new patent rights. Coffin's management also led the company towards an aggressive policy of buy-outs and mergers with competitors. Both strategies reduced competition in
1742-548: The United States , incandescent light bulbs including halogen bulbs stopped being sold as of August 1, 2023, because they do not meet minimum lumens per watt performance metrics established by the U.S. Department of Energy . Compact fluorescent bulbs are also banned despite their lumens per watt performance because of their toxic mercury that can be released into the home if broken and widespread problems with proper disposal of mercury-containing bulbs. In its modern form,
1809-540: The voltaic pile , the first electric battery. Current from these batteries could heat copper wire to incandescence. Vasily Vladimirovich Petrov developed the first persistent electric arc in 1802, and English chemist Humphry Davy gave a practical demonstration of an arc light in 1806. It took more than a century of continuous and incremental improvement, including numerous designs, patents, and resulting intellectual property disputes, to get from these early experiments to commercially produced incandescent light bulbs in
1876-437: The 1870s for large building and street lighting until it was superseded in the early 20th century by the incandescent light. Carbon arc lamps operate at high power and produce high intensity white light. They also are a point source of light. They remained in use in limited applications that required these properties, such as movie projectors , stage lighting , and searchlights , until after World War II. A discharge lamp has
1943-429: The 1880s: František Křižík invented in 1880 a mechanism to allow the automatic adjustment of the electrodes. The arcs were enclosed in a small tube to slow the carbon consumption (increasing the life span to around 100 hours). Flame arc lamps were introduced where the carbon rods had metal salts (usually magnesium, strontium, barium, or calcium fluorides) added to increase light output and produce different colours. In
2010-514: The 1900s the Phoebus cartel formed in an attempt to reduce the life of electric light bulbs, an example of planned obsolescence . Some types of lamp are also sensitive to switching cycles. Rooms with frequent switching, such as bathrooms, can expect much shorter lamp life than what is printed on the box. Compact fluorescent lamps are particularly sensitive to switching cycles. The total amount of artificial light (especially from street light )
2077-400: The 1920s, carbon arc lamps were sold as family health products, a substitute for natural sunlight. Arc lamps were superseded by filament lamps in most roles, remaining in only certain niche applications such as cinema projection , spotlights , and searchlights. In the 1950s and 1960s the high-power D.C. for the carbon-arc lamp of an outdoor drive-in projector would typically be supplied by
Electric light (disambiguation) - Misplaced Pages Continue
2144-446: The 1920s. In 1840, Warren de la Rue enclosed a platinum coil in a vacuum tube and passed an electric current through it, thus creating one of the world's first electric light bulbs . The design was based on the concept that the high melting point of platinum would allow it to operate at high temperatures and that the evacuated chamber would contain fewer gas molecules to react with the platinum, improving its longevity. Although it
2211-455: The 1970s. In the 2000s, efficacy and output have risen to the point where LEDs are now being used in lighting applications such as car headlights and brake lights, in flashlights and bicycle lights, as well as in decorative applications, such as holiday lighting. Indicator LEDs are known for their extremely long life, up to 100,000 hours, but lighting LEDs are operated much less conservatively, and consequently have shorter lives. LED technology
2278-541: The Kenner Easy-Bake Oven . Lamps can also be used for light therapy to deal with such issues as vitamin D deficiency , skin conditions such as acne and dermatitis , skin cancers , and seasonal affective disorder . Lamps which emit a specific frequency of blue light are also used to treat neonatal jaundice with the treatment which was initially undertaken in hospitals being able to be conducted at home. Electric lamps can also be used as
2345-493: The U.S., patent protection of arc-lighting systems and improved dynamos proved difficult and as a result the arc-lighting industry became highly competitive. Brush's principal competition was from the team of Elihu Thomson and Edwin J. Houston . These two had formed the American Electric Corporation in 1880, but it was soon bought up by Charles A. Coffin , moved to Lynn, Massachusetts , and renamed
2412-581: The UK and Thomas Edison in the US independently developing functional incandescent lamps. Swan's bulbs, based on designs by William Staite, were successful, but the filaments were too thick. Edison worked to create bulbs with thinner filaments, leading to a better design. The rivalry between Swan and Edison eventually led to a merger, forming the Edison and Swan Electric Light Company . By the early twentieth century these had completely replaced arc lamps . The turn of
2479-453: The UV-C. Most of the visible and IR radiation is produced from incandescence created at the positive electrode, or anode. Unlike the tungsten anodes found in other arc lamps, which remain relatively cool, carbon produces much higher resistance and the electrons are forced to enter the anode at the hottest point, generating tremendous amounts of heat that vaporizes the carbon and creates a pit in
2546-401: The anode's surface. This pit is heated from 6000 to 6500 degrees Fahrenheit (3300 to 3600 degrees Celsius, just below its melting point), causing it to glow very brightly with incandescence. Due to this, the electrodes were often placed at right angles from each other with the anode facing outward to keep from blocking its light output. Since carbon has the highest melting point of any element, it
2613-626: The appearance of an illuminated lightbulb above a person's head — signifies sudden inspiration. In the Middle East , a light bulb symbol has a sexual connotation. A stylized depiction of a light bulb features as the logo of the Turkish AK Party . Arc lamp An arc lamp or arc light is a lamp that produces light by an electric arc (also called a voltaic arc). The carbon arc light, which consists of an arc between carbon electrodes in air, invented by Humphry Davy in
2680-413: The applications which formerly used the carbon arc, such as movie projectors and searchlights. An arc is the discharge that occurs when a gas is ionized . A high voltage is pulsed across the lamp to "ignite" or "strike" the arc, after which the discharge can be maintained at a lower voltage. The "strike" requires an electrical circuit with an igniter and a ballast . The ballast is wired in series with
2747-406: The arc is passed in series through a solenoid attached to the top electrode. If the points of the electrodes are touching (as in start up) the resistance falls, the current increases and the increased pull from the solenoid draws the points apart. If the arc starts to fail the current drops and the points close up again. The Yablochkov candle is a simple arc lamp without a regulator, but it has
Electric light (disambiguation) - Misplaced Pages Continue
2814-559: The arc was encased in a glass globe, it was found that many of these invisible rays could be blocked. However, carbon-arcs were soon displaced by safer, more efficient, versatile, and easier to maintain incandescent and gas-discharge lamps. Carbon-arc lamps are still used where a close approximation of sunlight is needed, for testing materials, paints, and coatings for wear, fading, or deterioration, or, for example, spacecraft materials that are to be exposed to sunlight at orbits closer than Earth's. The arc consists of pure carbon-vapor heated to
2881-440: The arc. When the lamp sustains the arc, the ballast performs its second function, to limit the current to that needed to operate the lamp. The lamp, ballast, and igniter are rating-matched to each other; these parts must be replaced with the same rating as the failed component or the lamp will not work. The colour of the light emitted by the lamp changes as its electrical characteristics change with temperature and time. Lightning
2948-416: The carbon rods are short-lived and require constant adjustment in use, as the intense heat of the arc erodes them. The lamps produce significant ultraviolet output, they require ventilation when used indoors, and due to their intensity they need protection from direct sight. Invented by Humphry Davy around 1805, the carbon arc was the first practical electric light. It was used commercially beginning in
3015-438: The carbon vaporizes. The rods are slowly burnt away in use, and the distance between them needs to be regularly adjusted in order to maintain the arc. Many ingenious mechanisms were invented to control the distance automatically, mostly based on solenoids . In one of the simplest mechanically-regulated forms (which was soon superseded by more smoothly acting devices) the electrodes are mounted vertically. The current supplying
3082-428: The century saw further improvements in bulb longevity and efficiency, notably with the introduction of the tungsten filament by William D. Coolidge , who applied for a patent in 1912. This innovation became a standard for incandescent bulbs for many years. In 1910, Georges Claude introduced the first neon light, paving the way for neon signs which would become ubiquitous in advertising. In 1934, Arthur Compton ,
3149-400: The current flow (the ballast opposes any change in current through it); it cannot, as there is no longer a 'circuit'. As a result, a high voltage appears across the ballast momentarily, to which the lamp is connected; therefore the lamp receives this high voltage across it which 'strikes' the arc within the tube/lamp. The circuit will repeat this action until the lamp is ionized enough to sustain
3216-520: The drawbacks that the arc cannot be restarted (single use) and a limited lifetime of only a few hours. The spectrum emitted by a carbon-arc lamp is the closest to that of sunlight of any lamp. One of the first electric lights, their harsh, intense output usually limited their use to lighting large areas. Although invisible wavelengths were unknown at the time of their invention, unenclosed lamps were soon discovered to produce large amounts of infrared and harmful ultraviolet-radiation not found in sunlight. If
3283-661: The electrical lighting manufacturing industry. By 1890, the Thomson-Houston company was the dominant electrical manufacturing company in the U.S. Around the turn of the century arc-lighting systems were in decline, but Thomson-Houston controlled key patents to urban lighting systems. This control slowed the expansion of incandescent lighting systems being developed by Thomas Edison 's Edison General Electric Company . Conversely, Edison's control of direct current distribution and generating machinery patents blocked further expansion of Thomson-Houston. The roadblock to expansion
3350-577: The energy consumed is emitted as visible, usable light . The remaining 95% is lost as heat . In warmer climates, the emitted heat must then be removed, putting additional pressure on ventilation or air conditioning systems. In colder weather, the heat byproduct has some value, and has been successfully harnessed for warming in devices such as heat lamps . Incandescent bulbs are nonetheless being phased out in favor of technologies like CFLs and LED bulbs in many countries due to their low energy efficiency. The European Commission estimated in 2012 that
3417-687: The first city ever to be lit with "Brush Lights". Four of these lights became active there on March 31, 1880. Wabash was a small enough city to be lit entirely by 4 lights, whereas the installation at Cleveland's Public Square only lit a portion of that larger city. In 1880, Brush established the Brush Electric Company . The harsh and brilliant light was found most suitable for public areas, such as Cleveland's Public Square, being around 200 times more powerful than contemporary filament lamps . The usage of Brush electric arc lights spread quickly. Scientific American reported in 1881 that
SECTION 50
#17327871129723484-467: The first commercial uses for electricity, a phenomenon previously confined to experiment, the telegraph, and entertainment. In the United States, there were attempts to produce arc lamps commercially after 1850, but the lack of a constant electricity supply thwarted efforts. Thus electrical engineers began focusing on the problem of improving Faraday's dynamo . The concept was improved upon by
3551-438: The first decade of the 1800s, was the first practical electric light . It was widely used starting in the 1870s for street and large building lighting until it was superseded by the incandescent light in the early 20th century. It continued in use in more specialized applications where a high intensity point light source was needed, such as searchlights and movie projectors until after World War II . The carbon arc lamp
3618-437: The incandescent light bulb consists of a coiled filament of tungsten sealed in a globular glass chamber, either a vacuum or full of an inert gas such as argon . When an electric current is connected, the tungsten is heated to 2,000 to 3,300 K (1,730 to 3,030 °C; 3,140 to 5,480 °F) and glows, emitting light that approximates a continuous spectrum . Incandescent bulbs are highly inefficient, in that just 2–5% of
3685-536: The lamp again for several minutes (called cold restrike lamps). However, some lamps (mainly fluorescent tubes/energy saving lamps) can be restruck as soon as they are turned off (called hot restrike lamps). The Vortek water-wall plasma arc lamp, invented in 1975 by David Camm and Roy Nodwell at the University of British Columbia , Vancouver, Canada, made the Guinness Book of World Records in 1986 and 1993 as
3752-402: The lamp and performs two functions. First, when the power is first switched on, the igniter/starter (which is wired in parallel across the lamp) sets up a small current through the ballast and starter. This creates a small magnetic field within the ballast windings. A moment later the starter interrupts the current flow from the ballast, which has a high inductance and therefore tries to maintain
3819-429: The lamp's life. Some lasers have been adapted as an alternative to LEDs to provide highly focused illumination. Carbon arc lamps consist of two carbon rod electrodes in open air, supplied by a current-limiting ballast . The electric arc is struck by touching the rod tips then separating them. The ensuing arc produces a white-hot plasma between the rod tips. These lamps have higher efficacy than filament lamps, but
3886-406: The luminaire. Those designed for 12- or 24-volt operation have compact filaments, useful for good optical control. Also, they have higher efficacies (lumens per watt) and longer lives than non-halogen types. The light output remains almost constant throughout their life. Fluorescent lamps consist of a glass tube that contains mercury vapour or argon under low pressure. Electricity flowing through
3953-428: The most powerful continuously burning light source at over 300 kW or 1.2 million candle power. In a carbon arc lamp , the electrodes are carbon rods in free air. To ignite the lamp, the rods are touched together, thus allowing a relatively low voltage to strike the arc. The rods are then slowly drawn apart, and electric current heats and maintains an arc across the gap. The tips of the carbon rods are heated and
4020-410: The number of hours of operation at which 50% of them fail, that is the median life of the lamps. Production tolerances as low as 1% can create a variance of 25% in lamp life, so in general some lamps will fail well before the rated life expectancy, and some will last much longer. For LEDs, lamp life is defined as the operation time at which 50% of lamps have experienced a 70% decrease in light output. In
4087-631: The system was being used in: 800 lights in rolling mills, steel works, shops, 1,240 lights in woolen, cotton, linen, silk, and other factories, 425 lights in large stores, hotels, churches, 250 lights in parks, docks, and summer resorts, 275 lights in railroad depots and shops, 130 lights in mines, smelting works, 380 lights in factories and establishments of various kinds, 1,500 lights in lighting stations, for city lighting, 1,200 lights in England and other foreign countries. A total of over 6,000 lights which are actually sold. There were three major advances in
SECTION 60
#17327871129724154-419: The tube causes the gases to give off ultraviolet energy. The inside of the tubes are coated with phosphors that give off visible light when struck by ultraviolet photons . They have much higher efficiency than incandescent lamps. For the same amount of light generated, they typically use around one-quarter to one-third the power of an incandescent. The typical luminous efficacy of fluorescent lighting systems
4221-539: Was a major problem. In 1895, Hertha Ayrton wrote a series of articles for The Electrician , explaining that these phenomena were the result of oxygen coming into contact with the carbon rods used to create the arc. In 1899, she was the first woman ever to read her own paper before the Institution of Electrical Engineers (IEE). Her paper was "The Hissing of the Electric Arc". The arc lamp provided one of
4288-434: Was an efficient design, the cost of the platinum made it impractical for commercial use. William Greener , an English inventor, made significant contributions to early electric lighting with his lamp in 1846 (patent specification 11076), laying the groundwork for future innovations such as those by Thomas Edison. The late 1870s and 1880s were marked by intense competition and innovation, with inventors like Joseph Swan in
4355-410: Was due to the carbon rods used in projector lamphouses having a lifespan of roughly 22 minutes (which corresponds to the amount of film in said reels when projected at 24 frames/second). The projectionist would watch the rod burn down by eye (though a peephole like a welder's glass) and replace the carbon rod when changing film reels. The two-projector changeover setup largely disappeared in the 1970s with
4422-433: Was not a trivial exercise; as noted by Arthur A. Bright, "A great deal of experimentation had to be done on lamp sizes and shapes, cathode construction, gas pressures of both argon and mercury vapor, colors of fluorescent powders, methods of attaching them to the inside of the tube, and other details of the lamp and its auxiliaries before the new device was ready for the public." The first practical LED arrived in 1962. In
4489-486: Was removed when the two companies merged in 1892 to form the General Electric Company . Arc lamps were used in some early motion-picture studios to illuminate interior shots. One problem was that they produce such a high level of ultra-violet light that many actors needed to wear sunglasses when off camera to relieve sore eyes resulting from the ultra-violet light. The problem was solved by adding
#971028