Red is the color at the end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of 625–740 nanometres, it is a primary color in the RGB color model and the CMYK color model, is the complementary color of cyan. Reds range from the brilliant yellow-tinged scarlet and vermillion to bluish-red crimson, vary in shade from the pale red pink to the dark red burgundy; the red sky at sunset results from Rayleigh scattering, while the red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide. Iron oxide gives the red color to the planet Mars; the red colour of blood comes from protein hemoglobin, while ripe strawberries, red apples and reddish autumn leaves are colored by anthocyanins. Red pigment made from ochre was one of the first colors used in prehistoric art; the Ancient Egyptians and Mayans colored their faces red in ceremonies. It was an important color in China, where it was used to colour early pottery and the gates and walls of palaces.
In the Renaissance, the brilliant red costumes for the nobility and wealthy were dyed with kermes and cochineal. The 19th century brought the introduction of the first synthetic red dyes, which replaced the traditional dyes. Red became the color of revolution. Since red is the color of blood, it has been associated with sacrifice and courage. Modern surveys in Europe and the United States show red is the color most associated with heat, passion, anger and joy. In China and many other Asian countries it is the color of symbolizing happiness and good fortune. See below for shades of pink The human eye sees red when it looks at light with a wavelength between 625 and 740 nanometers, it is a primary color in the RGB color model and the light just past this range is called infrared, or below red, cannot be seen by human eyes, although it can be sensed as heat. In the language of optics, red is the color evoked by light that stimulates neither the S or the M cone cells of the retina, combined with a fading stimulation of the L cone cells.
Primates can distinguish the full range of the colors of the spectrum visible to humans, but many kinds of mammals, such as dogs and cattle, have dichromacy, which means they can see blues and yellows, but cannot distinguish red and green. Bulls, for instance, cannot see the red color of the cape of a bullfighter, but they are agitated by its movement.. One theory for why primates developed sensitivity to red is that it allowed ripe fruit to be distinguished from unripe fruit and inedible vegetation; this may have driven further adaptations by species taking advantage of this new ability, such as the emergence of red faces. Red light is used to help adapt night vision in low-light or night time, as the rod cells in the human eye are not sensitive to red. Red illumination was used as a safelight while working in a darkroom as it does not expose most photographic paper and some films. Today modern darkrooms use an amber safelight. On the color wheel long used by painters, in traditional color theory, red is one of the three primary colors, along with blue and yellow.
Painters in the Renaissance mixed red and blue to make violet: Cennino Cennini, in his 15th-century manual on painting, wrote, "If you want to make a lovely violet colour, take fine lac, ultramarine blue with a binder" he noted that it could be made by mixing blue indigo and red hematite. In modern color theory known as the RGB color model, red and blue are additive primary colors. Red and blue light combined together makes white light, these three colors, combined in different mixtures, can produce nearly any other color; this is the principle, used to make all of the colors on your computer screen and your television. For example, magenta on a computer screen is made by a similar formula to that used by Cennino Cennini in the Renaissance to make violet, but using additive colors and light instead of pigment: it is created by combining red and blue light at equal intensity on a black screen. Violet is made on a computer screen in a similar way, but with a greater amount of blue light and less red light.
So that the maximum number of colors can be reproduced on your computer screen, each color has been given a code number, or sRGB, which tells your computer the intensity of the red and blue components of that color. The intensity of each component is measured on a scale of zero to 255, which means the complete list includes 16,777,216 distinct colors and shades; the sRGB number of pure red, for example, is 255, 00, 00, which means the red component is at its maximum intensity, there is no green or blue. The sRGB number for crimson is 220, 20, 60, which means that the red is less intense and therefore darker, there is some green, which leans it toward orange; as a ray of white sunlight travels through the atmosphere to the eye, some of the colors are scattered out of the beam by air molecules and airborne particles due to Rayleigh scattering, changing the final color of the beam, seen. Colors with a shorter wavelength, such as blue and green, scatter more and are removed from the light that reaches the eye.
At sunrise and sunset, when the
Magenta is a color, variously defined as purplish-red, reddish-purple, purplish, or mauvish-crimson. In the RGB color model, it is made by mixing equal amounts of red. On color wheels of the RGB and CMY color models, it is located midway between blue, it is the complementary color of green. It is one of the four colors of ink used in color printing by an inkjet printer, along with yellow and cyan, to make all the other colors; the tone of magenta used in printing is called "printer's magenta". Magenta took its name from an aniline dye made and patented in 1859 by the French chemist François-Emmanuel Verguin, who called it fuchsine, it was renamed to celebrate the Italian-French victory at the Battle of Magenta fought between the French and Austrians on June 4, 1859, near the Italian town of Magenta in Lombardy. A identical color, called roseine, was created in 1860 by two British chemists: Chambers Nicolson and George Maule; the web color magenta is called fuchsia. Magenta is an extra-spectral color.
Rather, it is physiologically and psychologically perceived as the mixture of red and violet/blue light, with the absence of green. In the RGB color system, used to create all the colors on a television or computer display, magenta is a secondary color, made by combining equal amounts of red and blue light at a high intensity. In this system, magenta is the complementary color of green, combining green and magenta light on a black screen will create white. In the CMYK color model, used in color printing, it is one of the three primary colors, along with cyan and yellow, used to print all the rest of the colors. If magenta and yellow are printed on top of each other on a page, they make black. In this model, magenta is the complementary color of green, these two colors have the highest contrast and the greatest harmony. If combined and magenta ink will look dark gray or black; the magenta used in color printing, sometimes called process magenta, is a darker shade than the color used on computer screens.
A purple hue in terms of color theory, magenta is evoked by light having less power in green wavelengths than in blue/violet and red wavelengths. In the Munsell color system, magenta is called red–purple. If the spectrum is wrapped to form a color wheel, magenta appears midway between violet. Violet and red, the two components of magenta, are at opposite ends of the visible spectrum and have different wavelengths; the additive secondary color magenta, as noted above, is made by combining violet and red light at equal intensity. In optics and magenta are the same color; the web colors fuchsia and magenta are identical, are made by mixing the same proportions of blue and red light. In design and printing, there is a little more variation; the French version of fuchsia in the RGB color model and in printing contains a higher proportion of red than the American version of fuchsia. Fuchsia flowers themselves, which inspired both colors, have a variety of colors, from fuchsia to purple to red; the color magenta was the result of the industrial chemistry revolution of the mid-nineteenth century, which began with the invention by William Perkin of mauveine in 1856, the first synthetic aniline dye.
The enormous commercial success of the dye and the new color it produced, inspired other chemists in Europe to develop new colors made from aniline dyes. In France, François-Emmanuel Verguin, the director of the chemical factory of Louis Rafard near Lyon, tried many different formulae before in late 1858 or early 1859, mixing aniline with carbon tetrachloride, producing a reddish-purple dye which he called "fuchsine", after the color of the flower of the fuchsia plant, he quit the Rafard factory and took his color to a firm of paint manufacturers and Joseph Renard, who began to manufacture the dye in 1859. In the same year, two British chemists, Chambers Nicolson and George Maule, working at the laboratory of the paint manufacturer George Simpson, located in Walworth, south of London, made another aniline dye with a similar red-purple color, which they began to manufacture in 1860 under the name "roseine". In 1860 they changed the name of the color to "magenta", in honor of the Battle of Magenta fought between the French and Austrians at Magenta, Lombardy the year before, the new color became a commercial success.
Starting in 1935 the family of quinacridone dyes was developed. These have colors ranging from red to violet, so nowadays a quinacridone dye is used for magenta. Various tones of magenta—light, brilliant, rich, or deep—may be formulated by adding varying amounts of white to quinacridone artist's paints. Another dye used for magenta is Lithol Rubine BK. One of its uses is as a food coloring. In color printing, the color called process magenta, pigment magenta, or printer's magenta is one of the three primary pigment colors which, along with yellow and cyan, constitute the three subtractive primary colors of pigment; as such, the hue magenta is the complement of green: magenta pigments absorb green light. The CMYK printing process was invented in the 1890s, when newspapers began to publish color comic strips. Process magenta is not an RGB color, there is no fixed conversion from CMYK primaries to RGB. Different formulations are used for printer's ink, so there may be variations in the printed color, pure magenta ink.
A typical formulation of process magenta is shown in the color box at ri
Green is the color between blue and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of 495–570 nm. In subtractive color systems, used in painting and color printing, it is created by a combination of yellow and blue, or yellow and cyan. By far the largest contributor to green in nature is chlorophyll, the chemical by which plants photosynthesize and convert sunlight into chemical energy. Many creatures have adapted to their green environments by taking on a green hue themselves as camouflage. Several minerals have a green color, including the emerald, colored green by its chromium content. During post-classical and early modern Europe, green was the color associated with wealth, merchants and the gentry, while red was reserved for the nobility. For this reason, the costume of the Mona Lisa by Leonardo da Vinci and the benches in the British House of Commons are green while those in the House of Lords are red, it has a long historical tradition as the color of Ireland and of Gaelic culture.
It is the historic color of Islam, representing the lush vegetation of Paradise. It was the color of the banner of Muhammad, is found in the flags of nearly all Islamic countries. In surveys made in American and Islamic countries, green is the color most associated with nature, health, spring and envy. In the European Union and the United States, green is sometimes associated with toxicity and poor health, but in China and most of Asia, its associations are positive, as the symbol of fertility and happiness; because of its association with nature, it is the color of the environmental movement. Political groups advocating environmental protection and social justice describe themselves as part of the Green movement, some naming themselves Green parties; this has led to similar campaigns in advertising, as companies have sold green, or environmentally friendly, products. Green is the traditional color of safety and permission; the word green comes from the Middle English and Old English word grene, like the German word grün, has the same root as the words grass and grow.
It is from a Common Germanic *gronja-, reflected in Old Norse grænn, Old High German gruoni from a PIE root *ghre- "to grow", root-cognate with grass and to grow. The first recorded use of the word as a color term in Old English dates to ca. AD 700. Latin with viridis has a genuine and used term for "green". Related to virere "to grow" and ver "spring", it gave rise to words in several Romance languages, French vert, Italian verde; the Slavic languages with zelenъ. Ancient Greek had a term for yellowish, pale green – χλωρός, cognate with χλοερός "verdant" and χλόη "chloe, the green of new growth". Thus, the languages mentioned above have old terms for "green" which are derived from words for fresh, sprouting vegetation. However, comparative linguistics makes clear that these terms were coined independently, over the past few millennia, there is no identifiable single Proto-Indo-European or word for "green". For example, the Slavic zelenъ is cognate with Sanskrit hari "yellow, golden"; the Turkic languages have jašɨl "green" or "yellowish green", compared to a Mongolian word for "meadow".
In some languages, including old Chinese, old Japanese, Vietnamese, the same word can mean either blue or green. The Chinese character 青 has a meaning that covers both green. In more contemporary terms, they are 綠 respectively. Japanese has two terms that refer to the color green, 緑 and グリーン. However, in Japan, although the traffic lights have the same colors as other countries have, the green light is described using the same word as for blue, because green is considered a shade of aoi. Vietnamese uses a single word for both blue and green, with variants such as xanh da trời, lục. "Green" in modern European languages corresponds to about 520–570 nm, but many historical and non-European languages make other choices, e.g. using a term for the range of ca. 450–530 nm and another for ca. 530–590 nm. In the comparative study of color terms in the world's languages, green is only found as a separate category in languages with the developed range of six colors, or more in systems with five colors; these languages have introduced supplementary vocabulary to denote "green", but these terms are recognizable as recent adoptions that are not in origin color terms.
Thus, the Thai word เขียว kheīyw, besides mean
Cadmium is a chemical element with symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of its compounds, like mercury, it has a lower melting point than the transition metals in groups 3 through 11. Cadmium and its congeners in group 12 are not considered transition metals, in that they do not have filled d or f electron shells in the elemental or common oxidation states; the average concentration of cadmium in Earth's crust is between 0.5 parts per million. It was discovered in 1817 by Stromeyer and Hermann, both in Germany, as an impurity in zinc carbonate. Cadmium is a byproduct of zinc production. Cadmium was used for a long time as a corrosion-resistant plating on steel, cadmium compounds are used as red and yellow pigments, to color glass, to stabilize plastic. Cadmium use is decreasing because it is toxic and nickel-cadmium batteries have been replaced with nickel-metal hydride and lithium-ion batteries.
One of its few new uses is cadmium telluride solar panels. Although cadmium has no known biological function in higher organisms, a cadmium-dependent carbonic anhydrase has been found in marine diatoms. Cadmium is a soft, ductile, bluish-white divalent metal, it forms complex compounds. Unlike most other metals, cadmium is resistant to corrosion and is used as a protective plate on other metals; as a bulk metal, cadmium is not flammable. Although cadmium has an oxidation state of +2, it exists in the +1 state. Cadmium and its congeners are not always considered transition metals, in that they do not have filled d or f electron shells in the elemental or common oxidation states. Cadmium burns in air to form brown amorphous cadmium oxide. Hydrochloric acid, sulfuric acid, nitric acid dissolve cadmium by forming cadmium chloride, cadmium sulfate, or cadmium nitrate; the oxidation state +1 can be produced by dissolving cadmium in a mixture of cadmium chloride and aluminium chloride, forming the Cd22+ cation, similar to the Hg22+ cation in mercury chloride.
Cd + CdCl2 + 2 AlCl3 → Cd22The structures of many cadmium complexes with nucleobases, amino acids, vitamins have been determined. Occurring cadmium is composed of 8 isotopes. Two of them are radioactive, three are expected to decay but have not done so under laboratory conditions; the two natural radioactive isotopes are 116Cd. The other three are 106Cd, 108Cd, 114Cd. At least three isotopes – 110Cd, 111Cd, 112Cd – are stable. Among the isotopes that do not occur the most long-lived are 109Cd with a half-life of 462.6 days, 115Cd with a half-life of 53.46 hours. All of the remaining radioactive isotopes have half-lives of less than 2.5 hours, the majority have half-lives of less than 5 minutes. Cadmium has 8 known meta states, with the most stable being 113mCd, 115mCd, 117mCd; the known isotopes of cadmium range in atomic mass from 94.950 u to 131.946 u. For isotopes lighter than 112 u, the primary decay mode is electron capture and the dominant decay product is element 47. Heavier isotopes decay through beta emission producing element 49.
One isotope of cadmium, 113Cd, absorbs neutrons with high selectivity: With high probability, neutrons with energy below the cadmium cut-off will be absorbed. The cadmium cut-off is about 0.5 eV, neutrons below that level are deemed slow neutrons, distinct from intermediate and fast neutrons. Cadmium is created via the s-process in low- to medium-mass stars with masses of 0.6 to 10 solar masses, over thousands of years. In that process, a silver atom captures a neutron and undergoes beta decay. Cadmium was discovered in 1817 by Friedrich Stromeyer and Karl Samuel Leberecht Hermann, both in Germany, as an impurity in zinc carbonate. Stromeyer found the new element as an impurity in zinc carbonate, for 100 years, Germany remained the only important producer of the metal; the metal was named after the Latin word for calamine. Stromeyer noted that some impure samples of calamine changed color when heated but pure calamine did not, he was persistent in studying these results and isolated cadmium metal by roasting and reducing the sulfide.
The potential for cadmium yellow as pigment was recognized in the 1840s, but the lack of cadmium limited this application. Though cadmium and its compounds are toxic in certain forms and concentrations, the British Pharmaceutical Codex from 1907 states that cadmium iodide was used as a medication to treat "enlarged joints, scrofulous glands, chilblains". In 1907, the International Astronomical Union defined the international ångström in terms of a red cadmium spectral line. This
Hue is one of the main properties of a color, defined technically, as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, green and yellow". Hue can be represented quantitatively by a single number corresponding to an angular position around a central or neutral point or axis on a colorspace coordinate diagram or color wheel, or by its dominant wavelength or that of its complementary color; the other color appearance parameters are colorfulness, saturation and brightness. Colors with the same hue are distinguished with adjectives referring to their lightness or colorfulness, such as with "light blue", "pastel blue", "vivid blue". Exceptions include brown, a dark orange. In painting color theory, a hue is a pure pigment -- one without shade. Hues are first processed in the brain in areas in the extended V4 called globs. In opponent color spaces in which two of the axes are perceptually orthogonal to lightness, such as the CIE 1976 and 1976 color spaces, hue may be computed together with chroma by converting these coordinates from rectangular form to polar form.
Hue is the angular component of the polar representation. In CIELAB h a b = a t a n 2, analogously, in CIELUV h u v = a t a n 2 = a t a n 2, atan2 is a two-argument inverse tangent. Preucil describes a color hexagon, similar to a trilinear plot described by Evans and Brewer, which may be used to compute hue from RGB. To place red at 0°, green at 120°, blue at 240°, h r g b = a t a n 2. Equivalently, one may solve tan = 3 ⋅ 2 ⋅ R − G − B. Preucil used a polar plot. Using R, G, B, one may compute hue angle using the following scheme: determine which of the six possible orderings of R, G, B prevail apply the formula given in the table below. Note that in each case the formula contains the fraction M − L H − L, where H is the highest of R, G, B; this is referred to as the "Preucil hue error" and was used in the computation of mask strength in photomechanical color reproduction. Hue angles computed for the Preucil circle agree with the hue angle computed for the Preucil hexagon at integer multiples of 30° and differ by 1.2° at odd integer multiples of 15°, the maximal divergence between the two.
The process of converting an RGB color into an HSL color space or HSV color space is based on a 6-piece piecewise mapping, treating the HSV cone as a hexacone, or the HSL double cone as a double hexacone. The formulae used are those in the table above; the hues exhibited by caramel colorings and beers are limited in range. The Linner hue index is used to quantify the hue of such products. Manufacturers of pigments use the word hue, for example, "cadmium yellow" to indicate that the original pigmentation ingredient toxic, has been replaced by safer alternatives whilst retaining the hue of the original. Replacements are used for chromium and alizarin. Dominant wavelength is a physical analog to the perceptual attribute hue. On a chromaticity diagram, a line is drawn from a white point through the coordinates of the color in question, until it intersects the spectral locus; the wavelength at which the line intersects the spectrum locus is identified as the color's dominant wavelength if the point is on the same side of the white point as the spectral locus, as the color's complementary wavelength if the point is on the opposite side.
Δ h or Δ H ∗? There are two main ways; the first is the si
Cyan is a greenish-blue color. It is evoked by light with a predominant wavelength of between 490–520 nm, between the wavelengths of green and blue. In the subtractive color system, or CMYK, which can be overlaid to produce all colors in paint and color printing, cyan is one of the primary colors, along with magenta and black. In the additive color system, or RGB color model, used to create all the colors on a computer or television display, cyan is made by mixing equal amounts of green and blue light. Cyan is the complement of red. Mixing red light and cyan light at the right intensity will make white light; the web color cyan is synonymous with aqua. Other colors in the cyan color range are teal, electric blue and others described as blue-green, its name is derived from the Ancient Greek κύανος, transliterated kyanos, meaning "dark blue, dark blue enamel, Lapis lazuli". It was known as "cyan blue" or cyan-blue, its first recorded use as a color name in English was in 1879. Further origins of the color name can be traced back to a dye produced from the cornflower.
In most languages,'cyan' is not a basic color term and it phenomenologically appears as a greenish vibrant hue of blue to most English speakers. Reasons for why cyan is not linguistically acknowledged as a basic color term can be found in the frequent lack of distinction between blue and green in many languages; the web color cyan shown at right is a secondary color in the RGB color model, which uses combinations of red and blue light to create all the colors on computer and television displays. In X11 colors, this color is called both aqua. In the HTML color list, this same color is called aqua; the web colors are more vivid than the cyan used in the CMYK color system, the web colors cannot be reproduced on a printed page. To reproduce the web color cyan in inks, it is necessary to add some white ink to the printer's cyan below, so when it is reproduced in printing, it is not a primary subtractive color, it is called aqua because it is a color associated with water, such as the appearance of the water at a tropical beach.
Cyan is one of the common inks used in four-color printing, along with magenta and black. While both the additive secondary and the subtractive primary are called cyan, they can be different from one another. Cyan printing ink can be more saturated or less saturated than the RGB secondary cyan, depending on what RGB color space and ink are considered. Process cyan is not an RGB color, there is no fixed conversion from CMYK primaries to RGB. Different formulations are used for printer's ink, so there can be variations in the printed color, pure cyan ink; this is because real-world subtractive color mixing does not produce the same result when mixing identical colors, since the specific frequencies filtered out to produce that color affect how it interacts with other colors. Phthalocyanine blue is one such used pigment. A typical formulation of process cyan is shown in the color box at right. Pure water is nearly colorless. However, it does absorb more red light than blue, giving large volumes of water a bluish tint.
Cyanide derives its name from a blue pigment containing the cyanide ion. Cyanobacteria are an important link in the food chain; the planet Uranus is colored cyan because of the abundance of methane in its atmosphere. Methane absorbs red light and reflects the blue-green light which allows observers to see it as cyan. Natural gas, used by many for home cooking on gas stoves, has a cyan colored flame when burned with a mixture of air. Cyanotype, or blueprint, a monochrome photographic printing process that predates the use of the word cyan as a color, yields a deep cyan-blue colored print based on the Prussian blue pigment. Cinecolor, a bi-pack color process, the photographer would load a standard camera with two films, one orthochromatic, dyed red, a panchromatic strip behind it. Color light would expose the cyan record on the ortho stock, which acted as a filter, exposing only red light to the panchromatic film stock. Cyanosis is an abnormal blueness of the skin a sign of poor oxygen intake. I.e. the patient is "cyanotic".
Cyan is associated with the throat chakra in vedic medicine. In the 19th century, surgeons wore white gowns, but in the 20th century surgeons began to wear cyan or green surgical gowns, for several reasons. First, in the brightly lit operating room, cyan reflected less light than white and caused less strain on the eyes of the medical team. Second, cyan is the complementary color of red, so red blood on a cyan gown looks black or gray rather than red, is not as vivid. Shifting your sight to cyan after staring at red for long periods of time does not cause cyan after-images, as shifting from red to white will do. Lastly, since cyan is considered a restful and soothing color, it causes less anxiety in patients. Blue–green distinction in language Shades of cyan List of colors
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target, it is not proportional to luminance. This is a subjective attribute/property of an object being observed and one of the color appearance parameters of color appearance models. Brightness should not be confused with Lightness; the adjective bright derives from an Old English beorht with the same meaning via metathesis giving Middle English briht. The word is from a Common Germanic *berhtaz from a PIE root with a related meaning, *bhereg- "white, bright". "Brightness" was used as a synonym for the photometric term luminance and for the radiometric term radiance. As defined by the US Federal Glossary of Telecommunication Terms, "brightness" should now be used only for non-quantitative references to physiological sensations and perceptions of light. A given target luminance can elicit different perceptions of brightness in different contexts.
In the RGB color space, brightness can be thought of as the arithmetic mean μ of the red and blue color coordinates: μ = R + G + B 3 Brightness is a color coordinate in HSL color space: hue and lightness, meaning here brightness. With regard to stars, brightness is quantified as absolute magnitude. Brightness is, at least in some respects, the antonym of darkness; the United States Federal Trade Commission has assigned an unconventional meaning to brightness when applied to lamps. When appearing on light bulb packages, brightness means luminous flux, while in other contexts it means luminance. Luminous flux is the total amount such as a lighting device. Luminance, the original meaning of brightness, is the amount of light per solid angle coming from an area, such as the sky; the table below shows the standard ways of indicating the amount of light. The term "brightness" is used in discussions of sound timbres, in a rough analogy with visual brightness. Timbre researchers consider brightness to be one of the perceptually strongest distinctions between sounds, formalize it acoustically as an indication of the amount of high-frequency content in a sound, using a measure such as the spectral centroid.
Luma Luminance Luminosity Media related to brightness at Wikimedia Commons Poynton's Color FAQ