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82-481: The International Commission on Illumination (usually abbreviated CIE for its French name) is the body responsible for publishing all of the well-known standard illuminants. Each of these is known by a letter or by a letter-number combination. Illuminants A, B, and C were introduced in 1931, with the intention of respectively representing average incandescent light, direct sunlight, and average daylight. Illuminants D (1967) represent variations of daylight, illuminant E

164-407: A phase-out of incandescent light bulbs to reduce energy consumption. Historians Robert Friedel and Paul Israel list inventors of incandescent lamps prior to Joseph Swan and Thomas Edison of General Electric . They conclude that Edison's version was the first practical implementation, able to outstrip the others because of a combination of four factors: an effective incandescent material;

246-434: A vacuum higher than other implementations which was achieved through the use of a Sprengel pump ; a high resistance that made power distribution from a centralized source economically viable, and the development of the associated components required for a large-scale lighting system. Historian Thomas Hughes has attributed Edison's success to his development of an entire, integrated system of electric lighting. The lamp

328-538: A white point , corresponding to a correlated color temperature of 6504 K. Rec. 709 , used in HDTV systems, truncates the CIE 1931 coordinates to x=0.3127, y=0.329. There are no actual daylight light sources, only simulators. Constructing a practical light source that emulates a D-series illuminant is a difficult problem. The chromaticity can be replicated simply by taking a well known light source and applying filters, such as

410-428: A Canadian patent was filed by Henry Woodward and Mathew Evans for a lamp consisting of carbon rods mounted in a nitrogen-filled glass cylinder. They were unsuccessful at commercializing their lamp, and sold rights to their patent to Thomas Edison in 1879. (Edison needed ownership of the novel claim of lamps connected in a parallel circuit.) The government of Canada maintains that it is Woodward and Evans who invented

492-493: A Hungarian patent (No. 34541) for a tungsten filament lamp that lasted longer and gave brighter light than the carbon filament. Tungsten filament lamps were first marketed by the Hungarian company Tungsram in 1904. This type is often called Tungsram-bulbs in many European countries. Filling a bulb with an inert gas such as argon or nitrogen slows down the evaporation of the tungsten filament compared to operating it in

574-513: A carbon conductor, and platinum lead-in wires. This bulb lasted about 40 hours. Swan then turned his attention to producing a better carbon filament and the means of attaching its ends. He devised a method of treating cotton to produce 'parchmentised thread' in the early 1880s and obtained British Patent 4933 that same year. From this year he began installing light bulbs in homes and landmarks in England. His house, Underhill, Low Fell, Gateshead ,

656-472: A carbonized bamboo filament could last more than 1200 hours. In 1880, the Oregon Railroad and Navigation Company steamer, Columbia , became the first application for Edison's incandescent electric lamps (it was also the first ship to use a dynamo ). Albon Man, a New York lawyer, started Electro-Dynamic Light Company in 1878 to exploit his patents and those of William Sawyer . Weeks later

738-466: A coiled platinum filament in a vacuum tube and passed an electric current through it. 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 a workable design, the cost of the platinum made it impractical for commercial use. In 1841, Frederick de Moleyns of England

820-502: A color temperature, but it can be approximated by a D series illuminant with a CCT of 5455 K. (Of the canonical illuminants, D 55 is the closest.) Manufacturers sometimes compare light sources against illuminant E to calculate the excitation purity . The F series of illuminants represent various types of fluorescent lighting . F1–F6 "standard" fluorescent lamps consist of two semi-broadband emissions of antimony and manganese activations in calcium halophosphate phosphor . F4

902-504: A constant electric light at a public meeting in Dundee, Scotland . He stated that he could "read a book at a distance of one and a half feet". However he did not develop the electric light any further. In 1838, Belgian lithographer Marcellin Jobard invented an incandescent light bulb with a vacuum atmosphere using a carbon filament. In 1840, British scientist Warren De la Rue enclosed

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984-478: A glass receiver, hermetically sealed, and filled with nitrogen, electrically arranged so that the current could be passed to the second carbon when the first had been consumed. Later he lived in the US, changed his name to Alexander de Lodyguine and applied for and obtained patents for incandescent lamps having chromium , iridium , rhodium , ruthenium , osmium , molybdenum and tungsten filaments. On 24 July 1874,

1066-448: A lamp with inert gas instead of a vacuum resulted in twice the luminous efficacy and reduced bulb blackening. In 1917, Burnie Lee Benbow was granted a patent for the coiled coil filament , in which a coiled filament is then itself wrapped into a coil by use of a mandrel . In 1921, Junichi Miura created the first double-coil bulb using a coiled coil tungsten filament while working for Hakunetsusha (a predecessor of Toshiba ). At

1148-406: A lower resistivity than carbon, the tantalum lamp filament was quite long and required multiple internal supports. The metal filament gradually shortened in use; the filaments were installed with large slack loops. Lamps used for several hundred hours became quite fragile. Metal filaments had the property of breaking and re-welding, though this would usually decrease resistance and shorten the life of

1230-486: A meeting of the Literary and Philosophical Society of Newcastle upon Tyne on 3 February 1879. These lamps used a carbon rod from an arc lamp rather than a slender filament. Thus they had low resistance and required very large conductors to supply the necessary current, so they were not commercially practical, although they did furnish a demonstration of the possibilities of incandescent lighting with relatively high vacuum,

1312-400: A pair of chromaticity coordinates . If an image is recorded in tristimulus coordinates (or in values which can be converted to and from them), then the white point of the illuminant used gives the maximum value of the tristimulus coordinates that will be recorded at any point in the image, in the absence of fluorescence . It is called the white point of the image. The process of calculating

1394-622: A perfectly reflecting (or transmitting) diffuser, and their correlated color temperatures (CCTs) are given below. The CIE chromaticity coordinates are given for both the 2 degree field of view (1931) and the 10 degree field of view (1964). The color swatches represent the color of each white point, automatically calculated by Misplaced Pages using the Color temperature template . International Commission on Illumination The International Commission on Illumination (usually abbreviated CIE for its French name Commission internationale de l'éclairage )

1476-698: A process of introducing red phosphorus as the so-called getter inside the bulb ), which allowed obtaining economic bulbs lasting 800 hours; his patent was acquired by Edison in 1898. In 1897, German physicist and chemist Walther Nernst developed the Nernst lamp , a form of incandescent lamp that used a ceramic globar and did not require enclosure in a vacuum or inert gas. Twice as efficient as carbon filament lamps, Nernst lamps were briefly popular until overtaken by lamps using metal filaments. US575002A patent on 01.Dec.1897 to Alexander Lodyguine (Lodygin, Russia) describes filament made of rare metals, amongst them

1558-428: A red LED. LED-RGB1 defines the white light produced by a tricolor LED mix. LED-V1 and V2 define LEDs with phosphor-converted violet light. The spectrum of a standard illuminant, like any other profile of light, can be converted into tristimulus values . The set of three tristimulus coordinates of an illuminant is called a white point . If the profile is normalized , then the white point can equivalently be expressed as

1640-527: A relatively high absorbance at the red end of the spectrum, effectively increasing the CCT of the incandescent lamp to daylight levels. This is similar in function to a CTB color gel that photographers and cinematographers use today, albeit much less convenient. Each filter uses a pair of solutions, comprising specific amounts of distilled water, copper sulfate , mannite , pyridine , sulfuric acid , cobalt , and ammonium sulfate . The solutions are separated by

1722-413: A representative of noon sunlight, with a correlated color temperature (CCT) of 4874 K, while C represented average day light with a CCT of 6774 K. Unfortunately, they are poor approximations of any phase of natural daylight, particularly in the short-wave visible and in the ultraviolet spectral ranges. Once more realistic simulations were achievable, illuminants B and C were deprecated in favor of

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1804-424: A result, the incandescent bulb became widely used in household and commercial lighting, for portable lighting such as table lamps, car headlamps , and flashlights , and for decorative and advertising lighting. Incandescent bulbs are much less efficient than other types of electric lighting. Less than 5% of the energy they consume is converted into visible light; the rest is lost as heat. The luminous efficacy of

1886-402: A ruling 8 October 1883, that Edison's patents were based on the prior art of William Sawyer and were invalid. Litigation continued for a number of years. Eventually on 6 October 1889, a judge ruled that Edison's electric light improvement claim for "a filament of carbon of high resistance" was valid. The main difficulty with evacuating the lamps was moisture inside the bulb, which split when

1968-513: A sheet of uncolored glass. The amounts of the ingredients are carefully chosen so that their combination yields a color temperature conversion filter; that is, the filtered light is still white. The D series of illuminants are designed to represent natural daylight and lie along the daylight locus. They are difficult to produce artificially, but are easy to characterize mathematically. By 1964, several spectral power distributions (SPDs) of daylight had been measured independently by H. W. Budde of

2050-499: A simple, quadratic relation, later known as the daylight locus: Characteristic vector analysis revealed that the SPDs could be satisfactorily approximated by using the mean (S 0 ) and first two characteristic vectors (S 1 and S 2 ): In simpler terms, the SPD of the studied daylight samples can be expressed as the linear combination of three, fixed SPDs. The first vector (S 0 )

2132-421: A source is defined as the ratio of its luminous efficacy to the maximum possible luminous efficacy, which is 683 lm/W. An ideal white light source could produce about 250 lumens per watt, corresponding to a luminous efficiency of 37%. For a given quantity of light, an incandescent light bulb consumes more power and emits more heat than most other types of electric light. In buildings where air conditioning

2214-527: A successful version of this the first synthetic filament. The light bulb invented by Cruto lasted five hundred hours as opposed to the forty of Edison's original version. In 1882 Munich Electrical Exhibition in Bavaria, Germany Cruto's lamp was more efficient than the Edison's one and produced a better, white light. In 1893, Heinrich Göbel claimed he had designed the first incandescent light bulb in 1854, with

2296-480: A system of lighting . In 1761, Ebenezer Kinnersley demonstrated heating a wire to incandescence . However such wires tended to melt or oxidize very rapidly (burn) in the presence of air. Limelight became a popular form of stage lighting in the early 19th century, by heating a piece of calcium oxide to incandescence with an oxyhydrogen torch . In 1802, Humphry Davy used what he described as "a battery of immense size", consisting of 2,000 cells housed in

2378-476: A thin carbonized bamboo filament of high resistance, platinum lead-in wires in an all-glass envelope, and a high vacuum. Judges of four courts raised doubts about the alleged Göbel anticipation , but there was never a decision in a final hearing due to the expiration of Edison's patent. Research work published in 2007 concluded that the story of the Göbel lamps in the 1850s is fictitious. Joseph Swan (1828–1914)

2460-936: A typical incandescent bulb for 120 V operation is 16 lumens per watt (lm/W), compared with 60 lm/W for a compact fluorescent bulb or 100 lm/W for typical white LED lamps . The heat produced by filaments is used in some applications, such as heat lamps in incubators , lava lamps , Edison effect bulbs, and the Easy-Bake Oven toy. Quartz envelope halogen infrared heaters are used for industrial processes such as paint curing and space heating. Incandescent bulbs typically have shorter lifetimes compared to other types of lighting; around 1,000 hours for home light bulbs versus typically 10,000 hours for compact fluorescents and 20,000–30,000 hours for lighting LEDs. Most incandescent bulbs can be replaced by fluorescent lamps , high-intensity discharge lamps , and light-emitting diode lamps (LED). Some governments have begun

2542-453: A vacuum. This allows for greater temperatures and therefore greater efficacy with less reduction in filament life. In 1906, William D. Coolidge developed a method of making "ductile tungsten" from sintered tungsten which could be made into filaments while working for General Electric Company . By 1911 General Electric had begun selling incandescent light bulbs with ductile tungsten wire. In 1913, Irving Langmuir found that filling

Standard illuminant - Misplaced Pages Continue

2624-624: A zero at 560 nm , since all the relative SPDs have been normalized about this point. In order to match all significant digits of the published data of the canonical illuminants the values of M 1 and M 2 have to be rounded to three decimal places before calculation of S D . Using the standard 2° observer , the CIE 1931 color space chromaticity coordinates of D65 are x = 0.31272 y = 0.32903 {\displaystyle {\begin{aligned}x&=0.31272\\y&=0.32903\end{aligned}}} and

2706-621: Is heated until it glows . The filament is enclosed in a glass bulb that is either evacuated or filled with inert gas to protect the filament from oxidation . Electric current is supplied to the filament by terminals or wires embedded in the glass. A bulb socket provides mechanical support and electrical connections. Incandescent bulbs are manufactured in a wide range of sizes, light output, and voltage ratings, from 1.5 volts to about 300 volts. They require no external regulating equipment , have low manufacturing costs , and work equally well on either alternating current or direct current . As

2788-463: Is of particular interest since it was used for calibrating the CIE color rendering index (the CRI formula was chosen such that F4 would have a CRI of 51). F7–F9 are "broadband" ( full-spectrum light ) fluorescent lamps with multiple phosphors, and higher CRIs. Finally, F10–F12 are narrow triband illuminants consisting of three "narrowband" emissions (caused by ternary compositions of rare-earth phosphors) in

2870-425: Is recommended to realize CIE standard illuminant D65 or any other illuminant D of different CCT. It is hoped that new developments in light sources and filters will eventually offer sufficient basis for a CIE recommendation. Nevertheless, they do provide a measure, called the metamerism index , to assess the quality of daylight simulators. The Metamerism Index tests how well five sets of metameric samples match under

2952-433: Is the equal-energy illuminant, while illuminants F (2004) represent fluorescent lamps of various composition. There are instructions on how to experimentally produce light sources ("standard sources") corresponding to the older illuminants. For the relatively newer ones (such as series D), experimenters are left to measure to profiles of their sources and compare them to the published spectra: At present no artificial source

3034-547: Is the international authority on light , illumination , colour , and colour spaces . It was established in 1913 as a successor to the Commission Internationale de Photométrie, which was founded in 1900, and is today based in Vienna, Austria . The CIE has six active divisions, each of which establishes technical committees to carry out its program: Two divisions are no longer active. The President of

3116-401: Is the mean of all the SPD samples, which is the best reconstituted SPD that can be formed with only a fixed vector. The second vector (S 1 ) corresponds to yellow–blue variation (along the locus), accounting for changes in the correlated color temperature due to proportion of indirect to direct sunlight. The third vector (S 2 ) corresponds to pink–green variation (across the locus) caused by

3198-411: Is used, incandescent lamps' heat output increases load on the air conditioning system. While heat from lights will reduce the need to run a building's heating system, the latter can usually produce the same amount of heat at lower cost than incandescent lights. The chart below lists the luminous efficacy and efficiency for several types of incandescent bulb. A longer chart in luminous efficacy compares

3280-606: The Edison and Swan United Electric Company (later known as Ediswan, and ultimately incorporated into Thorn Lighting Ltd ). Edison was initially against this combination, but Edison was eventually forced to cooperate and the merger was made. Eventually, Edison acquired all of Swan's interest in the company. Swan sold his US patent rights to the Brush Electric Company in June 1882. The United States Patent Office gave

3362-724: The National Research Council of Canada in Ottawa , H. R. Condit and F. Grum of the Eastman Kodak Company in Rochester, New York , and S. T. Henderson and D. Hodgkiss of Thorn Electrical Industries in Enfield (north London) , totaling among them 622 samples. Deane B. Judd , David MacAdam , and Günter Wyszecki analyzed these samples and found that the ( x , y ) chromaticity coordinates followed

Standard illuminant - Misplaced Pages Continue

3444-796: The United States Electric Lighting Company was organized. This company did not make their first commercial installation of incandescent lamps until the fall of 1880, at the Mercantile Safe Deposit Company in New York City, about six months after the Edison incandescent lamps had been installed on the Columbia . Hiram S. Maxim was the chief engineer at the US Electric Lighting Co. After the great success in

3526-653: The XYZ tristimulus values (normalized to Y = 100 ), are X = 95.047 Y = 100 .000 Z = 108.883 {\displaystyle {\begin{alignedat}{2}X&={}&95.047\\Y&={}&100{\phantom {.000}}\\Z&={}&108.883\end{alignedat}}} For the supplementary 10° observer , x = 0.31382 y = 0.33100 {\displaystyle {\begin{aligned}x&=0.31382\\y&=0.33100\end{aligned}}} and

3608-570: The electric arc , by passing high current between two pieces of charcoal. For the next 40 years much research was given to turning the carbon arc lamp into a practical means of lighting. The carbon arc itself was dim and violet in color, emitting most of its energy in the ultraviolet, but the positive electrode was heated to just below the melting point of carbon and glowed very brightly with incandescence very close to that of sunlight. Arc lamps burned up their carbon rods very rapidly, expelled dangerous carbon monoxide, and tended to produce outputs in

3690-463: The visible spectrum . It is useful as a theoretical reference; an illuminant that gives equal weight to all wavelengths. It also has equal CIE XYZ tristimulus values, thus its chromaticity coordinates are (x,y)=(1/3,1/3). This is by design; the XYZ color matching functions are normalized such that their integrals over the visible spectrum are the same. Illuminant E is not a black body, so it does not have

3772-460: The CIE from 2023 is Jennifer Veitch from Canada. CIE publishes Technical Reports (TRs), International Standards (ISs) and Technical Notes (TNs). International Standards (ISs) are often further developed as dual standards with the ISO or IEC . Incandescent lamp An incandescent light bulb , incandescent lamp or incandescent light globe is an electric light with a filament that

3854-546: The CIE today are derived by linear interpolation of the 10 nm data set down to 5 nm . However, there is a proposal to use spline interpolation instead. Similar studies have been undertaken in other parts of the world, or repeating Judd et al.' s analysis with modern computational methods. In several of these studies, the daylight locus is notably closer to the Planckian locus than in Judd et al. The CIE positions D65 as

3936-477: The D series. Illuminant C does not have the status of CIE standard illuminants but its relative spectral power distribution, tristimulus values and chromaticity coordinates are given in Table T.1 and Table T.3, as many practical measurement instruments and calculations still use this illuminant. Illuminant B was not so honored in 2004. The liquid filters, designed by Raymond Davis and Kasson S. Gibson in 1931, have

4018-556: The D-series SPD (S D ) that corresponds to those coordinates, the coefficients M 1 and M 2 of the characteristic vectors S 1 and S 2 are determined: where S 0 ( λ ) , S 1 ( λ ) , S 2 ( λ ) {\displaystyle S_{0}(\lambda ),S_{1}(\lambda ),S_{2}(\lambda )} are the mean and first two eigenvector SPDs, depicted in figure. The characteristic vectors both have

4100-491: The R,G,B regions of the visible spectrum. The phosphor weights can be tuned to achieve the desired CCT. The spectra of these illuminants are published in Publication 15:2004. Publication 15:2018 introduces new illuminants for different white LED types with CCTs ranging from approx. 2700 K to 6600 K. LED-B1 through B5 defines LEDs with phosphor-converted blue light. LED-BH1 defines a blend of phosphor-converted blue and

4182-467: The Spectralight III, that used filtered incandescent lamps. However, the SPDs of these sources deviate from the D-series SPD, leading to bad performance on the CIE metamerism index . Better sources were achieved in the 2010s with phosphor-coated white LEDs that can easily emulate the A, D, and E illuminants with high CRI. Illuminant E is an equal-energy radiator; it has a constant SPD inside

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4264-835: The United States, the incandescent light bulb patented by Edison also began to gain widespread popularity in Europe as well; among other places, the first Edison light bulbs in the Nordic countries were installed at the weaving hall of the Finlayson 's textile factory in Tampere, Finland in March 1882. Lewis Latimer , employed at the time by Edison, developed an improved method of heat-treating carbon filaments which reduced breakage and allowed them to be molded into novel shapes, such as

4346-469: The basement of the Royal Institution of Great Britain, to create an incandescent light by passing the current through a thin strip of platinum , chosen because the metal had an extremely high melting point . It was not bright enough nor did it last long enough to be practical, but it was the precedent behind the efforts of scores of experimenters over the next 75 years. Davy also demonstrated

4428-521: The characteristic "M" shape of Maxim filaments. On 17 January 1882, Latimer received a patent for the "Process of Manufacturing Carbons", an improved method for the production of light bulb filaments, which was purchased by the United States Electric Light Company. Latimer patented other improvements such as a better way of attaching filaments to their wire supports. In Britain, the Edison and Swan companies merged into

4510-529: The chromaticity coordinates must be determined: where T is the illuminant's CCT. Note that the CCTs of the canonical illuminants, D 50 , D 55 , D 65 , and D 75 , differ slightly from what their names suggest. For example, D50 has a CCT of 5003 K ("horizon" light), while D65 has a CCT of 6504 K (noon light). This is because the value of the constants in Planck's law have been slightly changed since

4592-495: The color temperature, the CIE now specifies the SPD directly, based on the original (1931) value of c 2 : The coefficients have been selected to achieve a normalized SPD of 100 at 560 nm . The tristimulus values are ( X , Y , Z ) = (109.85, 100.00, 35.58) , and the chromaticity coordinates using the standard observer are ( x , y ) = (0.44758, 0.40745) . Illuminants B and C are easily achieved daylight simulations. They modify illuminant A by using liquid filters. B served as

4674-423: The corresponding XYZ tristimulus values are X = 94.811 Y = 100 .000 Z = 107.304 {\displaystyle {\begin{alignedat}{2}X&={}&94.811\\Y&={}&100{\phantom {.000}}\\Z&={}&107.304\end{alignedat}}} Since D65 represents white light, its coordinates are also

4756-579: The cost of providing a given quantity of light by a factor of thirty, compared with the cost at introduction of Edison's lighting system. Consumption of incandescent light bulbs grew rapidly in the US. In 1885, an estimated 300,000 general lighting service lamps were sold, all with carbon filaments. When tungsten filaments were introduced, about 50 million lamp sockets existed in the US. In 1914, 88.5 million lamps were used, (only 15% with carbon filaments), and by 1945, annual sales of lamps were 795 million (more than 5 lamps per person per year). Less than 5% of

4838-660: The definition of these canonical illuminants, whose SPDs are based on the original values in Planck's law. The same discrepancy applies to all illuminants in the D series—D 50 , D 55 , D 65 , D 75 —and can be "rectified" by multiplying the nominal color temperature by c 2 1.4380 {\displaystyle {\frac {c_{2}}{1.4380}}} ; for example 6500   K × 1.438776877 … 1.4380 = 6503.51   K {\displaystyle 6500\ {\text{K}}\times {\frac {1.438776877\dots }{1.4380}}=6503.51\ {\text{K}}} for D 65 . To determine

4920-615: The filament. General Electric bought the rights to use tantalum filaments and produced them in the US until 1913. From 1898 to around 1905, osmium was also used as a filament in lamps made by Carl Auer von Welsbach . The metal was so expensive that used lamps could be returned for partial credit. It could not be made for 110 V or 220 V so several lamps were wired in series for use on standard voltage circuits. These were primarily sold in Europe. On 13 December 1904, Hungarian Sándor Just and Croatian Franjo Hanaman were granted

5002-489: The help of Charles Stearn, an expert on vacuum pumps, in 1878, Swan developed a method of processing that avoided the early bulb blackening. This received a British Patent in 1880. On 18 December 1878, a lamp using a slender carbon rod was shown at a meeting of the Newcastle Chemical Society , and Swan gave a working demonstration at their meeting on 17 January 1879. It was also shown to 700 who attended

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5084-518: The inside of lamp bulbs without weakening them. In 1947, he patented a process for coating the inside of lamps with silica . In 1930, Hungarian Imre Bródy filled lamps with krypton gas rather than argon, and designed a process to obtain krypton from air. Production of krypton filled lamps based on his invention started at Ajka in 1937, in a factory co-designed by Polányi and Hungarian-born physicist Egon Orowan . By 1964, improvements in efficiency and production of incandescent lamps had reduced

5166-415: The lamp was lit, with resulting oxygen attacking the filament. In the 1880s, phosphoric anhydride was used in combination with expensive mercury vacuum pumps . However, about 1893, Italian inventor Arturo Malignani  [ it ] (1865–1939), who lacked these pumps, discovered that phosphorus vapours did the job of chemically binding the remaining amounts of water and oxygen. In 1896 he patented

5248-442: The lightbulb. On 4 March 1880, just five months after Edison's light bulb, Alessandro Cruto created his first incandescent lamp. Cruto produced a filament by deposition of graphite on thin platinum filaments, by heating it with an electric current in the presence of gaseous ethyl alcohol . Heating this platinum at high temperatures leaves behind thin filaments of platinum coated with pure graphite. By September 1881 he had achieved

5330-543: The museum of the Château de Blois . In 1859, Moses G. Farmer built an electric incandescent light bulb using a platinum filament. Thomas Edison later saw one of these bulbs in a shop in Boston, and asked Farmer for advice on the electric light business. In 1872, Russian Alexander Lodygin invented an incandescent light bulb and obtained a Russian patent in 1874. He used as a burner two carbon rods of diminished section in

5412-412: The power consumed by a typical incandescent light bulb is converted into visible light, with most of the rest being emitted as invisible infrared radiation. Light bulbs are rated by their luminous efficacy , which is the ratio of the amount of visible light emitted ( luminous flux ) to the electrical power consumed. Luminous efficacy is measured in lumens per watt (lm/W). The luminous efficiency of

5494-552: The presence of water in the form of vapor and haze. By the time the D-series was formalized by the CIE, a computation of the chromaticity ( x , y ) {\displaystyle (x,y)} for a particular isotherm was included. Judd et al. then extended the reconstituted SPDs to 300 nm – 330 nm and 700 nm – 830 nm by using Moon's spectral absorbance data of the Earth's atmosphere. The tabulated SPDs presented by

5576-559: The relative SPD) and c 2 = h ⋅ c / k {\displaystyle c_{2}=h\cdot c/k} were different. In 1968, the estimate of c 2 was revised from 0.01438 m·K to 0.014388 m·K (and before that, it was 0.01435 m·K when illuminant A was standardized). This difference shifted the Planckian locus , changing the color temperature of the illuminant from its nominal 2848 K to 2856 K: In order to avoid further possible changes in

5658-430: The standard daylight illuminant: [D65] is intended to represent average daylight and has a correlated colour temperature of approximately 6500 K. CIE standard illuminant D65 should be used in all colorimetric calculations requiring representative daylight, unless there are specific reasons for using a different illuminant. Variations in the relative spectral power distribution of daylight are known to occur, particularly in

5740-471: The tens of kilowatts. Therefore, they were only practical for lighting large areas, so researchers continued to search for a way to make lamps suitable for home use. Over the first three-quarters of the 19th century, many experimenters worked with various combinations of platinum or iridium wires, carbon rods, and evacuated or semi-evacuated enclosures. Many of these devices were demonstrated and some were patented. In 1835, James Bowman Lindsay demonstrated

5822-498: The test and reference illuminant. In a manner similar to the color rendering index , the average difference between the metamers is calculated. The CIE defines illuminant A in these terms: CIE standard illuminant A is intended to represent typical, domestic, tungsten-filament lighting. Its relative spectral power distribution is that of a Planckian radiator at a temperature of approximately 2856 K. CIE standard illuminant A should be used in all applications of colorimetry involving

5904-577: The time, machinery to mass-produce coiled coil filaments did not exist. Hakunetsusha developed a method to mass-produce coiled coil filaments by 1936. Between 1924 and the outbreak of the Second World War, the Phoebus cartel attempted to fix prices and sales quotas for bulb manufacturers outside of North America. In 1925, Marvin Pipkin , an American chemist, patented a process for frosting

5986-460: The ultraviolet spectral region, as a function of season, time of day, and geographic location. The relative spectral power distribution (SPD) S D ( λ ) {\displaystyle S_{D}(\lambda )} of a D series illuminant can be derived from its chromaticity coordinates in the CIE 1931 color space , ( x D , y D ) {\displaystyle (x_{D},y_{D})} . First,

6068-408: The use of incandescent lighting, unless there are specific reasons for using a different illuminant. The spectral radiant exitance of a black body follows Planck's law : At the time of standardizing illuminant A, both c 1 = 2 π ⋅ h ⋅ c 2 {\displaystyle c_{1}=2\pi \cdot h\cdot c^{2}} (which does not affect

6150-404: The white point discards a great deal of information about the profile of the illuminant, and so although it is true that for every illuminant the exact white point can be calculated, it is not the case that knowing the white point of an image alone tells you a great deal about the illuminant that was used to record it. A list of standardized illuminants, their CIE chromaticity coordinates (x,y) of

6232-419: Was a British physicist and chemist. In 1850, he began working with carbonized paper filaments in an evacuated glass bulb. By 1860, he was able to demonstrate a working device but the lack of a good vacuum and an adequate supply of electricity resulted in a short lifetime for the bulb and an inefficient source of light. By the mid-1870s better pumps had become available, and Swan returned to his experiments. With

6314-462: Was a small component in his system of electric lighting, and no more critical to its effective functioning than the Edison Jumbo generator , the Edison main and feeder, and the parallel-distribution system. Other inventors with generators and incandescent lamps, and with comparable ingenuity and excellence, have long been forgotten because their creators did not preside over their introduction in

6396-497: Was granted the first patent for an incandescent lamp, with a design using platinum wires contained within a vacuum bulb. He also used carbon. In 1845, American John W. Starr patented an incandescent light bulb using carbon filaments. His invention was never produced commercially. In 1851, Jean Eugène Robert-Houdin publicly demonstrated incandescent light bulbs on his estate in Blois, France. His light bulbs are on display in

6478-507: Was lit by Joseph Swan's incandescent lamp on 3 February 1879. Thomas Edison began serious research into developing a practical incandescent lamp in 1878. Edison filed his first patent application for "Improvement in Electric Lights" on 14 October 1878. After many experiments, first with carbon in the early 1880s and then with platinum and other metals, in the end Edison returned to a carbon filament. The first successful test

6560-448: Was on 22 October 1879, and lasted 13.5 hours. Edison continued to improve this design and by 4 November 1879, filed for a US patent for an electric lamp using "a carbon filament or strip coiled and connected ... to platina contact wires." Although the patent described several ways of creating the carbon filament including using "cotton and linen thread, wood splints, papers coiled in various ways," Edison and his team later discovered that

6642-560: Was the first in the world to be lit by a lightbulb. In the early 1880s he had started his company. In 1881, the Savoy Theatre in the City of Westminster , London was lit by Swan incandescent lightbulbs, which was the first theatre, and the first public building in the world, to be lit entirely by electricity. The first street in the world to be lit by an incandescent lightbulb was Mosley Street, Newcastle upon Tyne , United Kingdom . It

6724-492: Was tungsten. Lodygin invented a process where rare metals such as tungsten can be chemically treated and heat-vaporized onto an electrically heated thread-like wire (platinum, carbon, gold) acting as a temporary base or skeletal form. (US patent 575,002). Lodygin later sold the patent rights to GE. In 1902, Siemens developed a tantalum lamp filament that was more efficient than even graphitized carbon filaments since they could operate at higher temperature. Since tantalum metal has

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