1.
CIE 1931 color space
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The CIE1931 color spaces were the first defined quantitative links between physical pure colors in the electromagnetic visible spectrum, and physiological perceived colors in human color vision. The CIE1931 RGB color space and CIE1931 XYZ color space were created by the International Commission on Illumination in 1931 and they resulted from a series of experiments done in the late 1920s by William David Wright and John Guild. The experimental results were combined into the specification of the CIE RGB color space, the CIE1931 color spaces are still widely used, as is the 1976 CIELUV color space. The human eye with normal vision has three kinds of cells, which sense light, with spectral sensitivity peaks in short, middle. These cone cells underlie human color perception under medium- and high-brightness conditions, thus, three parameters, corresponding to levels of stimulus of the three types of cone cells, can in principle describe any color sensation. The tristimulus values associated with a space can be conceptualized as amounts of three primary colors in a tri-chromatic additive color model. In some color spaces, including LMS and XYZ spaces, the colors used are not real colors. The CIE XYZ color space encompasses all color sensations that a person can experience. That is why CIE XYZ is a device invariant color representation and it serves as a standard reference against which many other color spaces are defined. Consider two light sources made up of different mixtures of various wavelengths, such light sources may appear to be the same color, this effect is called metamerism. Such light sources have the apparent color to an observer when they produce the same tristimulus values. Most wavelengths stimulate two or all three types of cell, because the spectral sensitivity curves of the three types of cone cells overlap. Certain tristimulus values are thus physically impossible, to avoid these negative RGB values, and to have one component that describes the perceived brightness, imaginary primary colors and corresponding color-matching functions have been formulated. The resulting tristimulus values are defined by the CIE1931 color space, in which they are denoted X, Y, and Z. When judging the relative luminance of different colors in well-lit situations, humans tend to perceive light within the green parts of the spectrum as brighter than red or blue light of equal power. The luminosity function that describes the perceived brightnesses of different wavelengths is thus analogous to the spectral sensitivity of M cones. The CIE model capitalises on this fact by defining Y as luminance, Z is quasi-equal to blue stimulation, or the S cone response, and X is a mix of cone response curves chosen to be nonnegative. The XYZ tristimulus values are thus analogous to, but different from, defining Y as luminance has the useful result that for any given Y value, the XZ plane will contain all possible chromaticities at that luminance
2.
Chromaticity
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Chromaticity is an objective specification of the quality of a color regardless of its luminance. Chromaticity consists of two independent parameters, often specified as hue and colorfulness, where the latter is called saturation, chroma, intensity. This number of parameters follows from trichromacy of vision of most humans, the hue is the angular component, and the purity is the radial component, normalized by the maximum radius for that hue. Purity is roughly equivalent to the saturation in the HSV color model. Some color spaces separate the three dimensions of color into one dimension and a pair of chromaticity dimensions. For example, the point of an sRGB display is an x, y chromaticity of. These pairs determine a chromaticity as affine coordinates on a triangle in a 2-space and these x and y are used because of simplicity of expression in CIE1931 and have no inherent advantage. Other coordinate systems on the same X-Y-Z triangle, or other color triangles, the xyY space is a cross between the CIE XYZ and its normalized chromaticity coordinates xyz, such that the luminance Y is preserved and augmented with just the required two chromaticity dimensions. CIE xyY Chrominance rg chromaticity Stanford University CS178 interactive Flash demo explaining chromaticity diagrams, chromaticity diagrams and LED binning explained, Edaphic Scientific Knowledge Base
3.
Color
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Color or colour is the characteristic of human visual perception described through color categories, with names such as red, yellow, purple, or blue. This perception of color derives from the stimulation of cells in the human eye by electromagnetic radiation in the spectrum of light. Color categories and physical specifications of color are associated with objects through the wavelength of the light that is reflected from them and this reflection is governed by the objects physical properties such as light absorption, emission spectra, etc. By defining a color space, colors can be identified numerically by coordinates, there may also be more than three color dimensions in other color spaces, such as in the CMYK color model, wherein one of the dimensions relates to a colours colorfulness). The photo-receptivity of the eyes of species also varies considerably from our own. Honeybees and bumblebees for instance have trichromatic color vision sensitive to ultraviolet but is insensitive to red, papilio butterflies possess six types of photoreceptors and may have pentachromatic vision. The most complex color vision system in the kingdom has been found in stomatopods with up to 12 spectral receptor types thought to work as multiple dichromatic units. The science of color is sometimes called chromatics, colorimetry, or simply color science and it includes the perception of color by the human eye and brain, the origin of color in materials, color theory in art, and the physics of electromagnetic radiation in the visible range. Electromagnetic radiation is characterized by its wavelength and its intensity, when the wavelength is within the visible spectrum, it is known as visible light. Most light sources emit light at different wavelengths, a sources spectrum is a distribution giving its intensity at each wavelength. Although the spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, in each such class the members are called metamers of the color in question. The table at right shows approximate frequencies and wavelengths for various pure spectral colors, the wavelengths listed are as measured in air or vacuum. A common list identifies six main bands, red, orange, yellow, green, blue, Newtons conception included a seventh color, indigo, between blue and violet. It is possible that what Newton referred to as blue is nearer to what today is known as cyan, the color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Some objects not only light, but also transmit light or emit light themselves. This effect is known as color constancy, opaque objects that do not reflect specularly have their color determined by which wavelengths of light they scatter strongly. If objects scatter all wavelengths with roughly equal strength, they appear white, if they absorb all wavelengths, they appear black. Opaque objects that reflect light of different wavelengths with different efficiencies look like mirrors tinted with colors determined by those differences
4.
Palette (computing)
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In computer graphics, a palette is a finite set of colors. Palettes can be optimized to improve accuracy in the presence of software or hardware constraints. Depending on the context, the palette and related terms such as Web palette. Selected colors or picked colors, In this case, the selection, generally from a wider explicitly available full palette, is always chosen by software. For example, the standard VGA display adapter is said to provide a palette of 256 simultaneous colors from a total of 262,144 different colors, default palette or system palette, The given selected colors have been officially standardized by some body or corporation. For example, the well known Web-safe colors for use with Internet browsers, on an individual image, color map or color table, The limited color selection is stored inside the given indexed color image file. For example, the registers of the Commodore Amiga are known both as their color palette and their CLUT, depending on sources. GUI palettes An arrangement of a set of user or system colors that can be chosen. In such cases, the color palette or user color palette are common equivalents. This usage resembles a true artists palette, a palette for choosing colors can be also a floating palette. An application can, in turn, show different image thumbnails in a mosaic on screen. It is obvious that the program cannot load all the adaptive palettes of every displayed image thumbnail at the time in the hardware color registers. A solution is to use a unique, common master palette or universal palette and this is done by selecting colors in such way that the master palette comprises a full RGB color space in miniature, limiting the possible levels that the red, green and blue components may have. This kind of arrangement is referred as a uniform palette. The normal human eye has sensibility to the three colors in different degrees, the more to the green, the less to the blue. So RGB arrangements can take advantage of this by assigning more levels for the green component and it is more general to use only 6R×6G×6B =216, 6R×8G×5B =240 or 6R×7G×6B =252, which leave room for some reserved colors. This way, and with further dithering, the color image can nearly match the original. But this creates a heavy dependence between the pixels and its adaptive palette
5.
Pantone
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Pantone Inc. is a corporation headquartered in Carlstadt, New Jersey. X-Rite Inc. a supplier of color measurement instruments and software, Pantone began in New York City in the 1950s as the commercial printing company of M & J Levine Advertising. In 1956, its founders, advertising executives brothers Mervin and Jesse Levine, for instance, a particular page might contain a number of yellows of varying tints. The idea behind the PMS is to allow designers to color match specific colors when a design enters production stage and this system has been widely adopted by graphic designers and reproduction and printing houses. Pantone recommends that PMS Color Guides be purchased annually, as their inks become yellowish over time, Color variance also occurs within editions based on the paper stock used, while interedition color variance occurs when there are changes to the specific paper stock used. The Pantone Color Matching System is largely a standardized color reproduction system, by standardizing the colors, different manufacturers in different locations can all refer to the Pantone system to make sure colors match without direct contact with one another. One such use is standardizing colors in the CMYK process, the CMYK process is a method of printing color by using four inks—cyan, magenta, yellow, and black. A majority of the printed material is produced using the CMYK process. Those that are possible to simulate through the CMYK process are labeled as such within the companys guides, however, most of the Pantone systems 1,114 spot colors cannot be simulated with CMYK but with 13 base pigments mixed in specified amounts. The Pantone system also allows for many special colors to be produced, such as metallics, while most of the Pantone system colors are beyond the printed CMYK gamut, it was only in 2001 that Pantone began providing translations of their existing system with screen-based colors. Screen-based colors use the RGB color model—red, green, blue—system to create various colors, the Goe system has RGB and LAB values with each color. Pantone colors are described by their allocated number, PMS colors are almost always used in branding and have even found their way into government legislation and military standards. In January 2003, the Scottish Parliament debated a petition to refer to the blue in the Scottish flag as Pantone 300, countries such as Canada and South Korea and organizations such as the FIA have also chosen to refer to specific Pantone colors to use when producing flags. US states including Texas have set legislated PMS colors of their flags and it has also been used in an art project by the Brazilian photographer Angelica Dass which applies Pantone to the human skin color spectrum. On September 5,2007, Pantone introduced the Goe System, Goe consisted of over 2,000 new colors in a new matching and numbering system. The Goe system was streamlined to use base colors and accommodate many technical challenges in reproducing colors on a press. The Pantone Goe system was discontinued in November 2013, in mid-2006 Pantone, partnering with Vermont-based Fine Paints of Europe, introduced a new line of interior and exterior paints. The color palette uses Pantones color research and trending and has more than 3,000 colors, in November 2015, Pantone partnered with Redland London to create a collection of bags inspired from Pantones authority on color
6.
Natural Color System
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The Natural Color System is a proprietary perceptual color model. It is based on the color opponency hypothesis of color vision, the current version of the NCS was developed by the Swedish Colour Centre Foundation, from 1964 onwards. The research team consisted of Anders Hård, Lars Sivik and Gunnar Tonnquist, the system is based entirely on the phenomenology of human perception and not on color mixing. It is illustrated by an atlas, marketed by NCS Colour AB in Stockholm. The last four are called unique hues. In the NCS all six are defined as elementary colors, irreducible qualia, all other experienced colors are considered composite perceptions, i. e. experiences that can be defined in terms of similarity to the six elementary colors. A saturated pink could be defined by its visual similarity to red, blue, black. Colors in the NCS are defined by three values, expressed in percentages, specifying the degree of blackness, chromaticness, and hue, no hue is considered to have visual similarity to both hues of an opponent pair, i. e. there is no redgreen or yellowblue. The blackness and the chromaticness together add up to less than or equal to 100%—their remainder from 100%, if any, gives the amount of whiteness. The complete NCS color notations can also be tagged with an S and it is also one of the standards used by the International Colour Authority, a leading publisher of color trend forecasts for the interior design and textile markets. The most important difference between NCS and most other color systems resides in their starting points, the aim of NCS is to define colors from their visual appearance, as they are experienced by human consciousness. Other color models, such as CMYK and RGB, are based on an understanding of physical processes, more problematic is the relation with the CMYK-model which is generally seen as a correct prediction of the behavior of mixing pigments, as a system of subtractive color. The NCS explains this by assuming that the behavior of paint is partly counterintuitive to human phenomenology. Observing that the mix of yellow and cyan paint results in a green color, Hering argued that yellow is not a redgreen but a unique hue. He concluded that Herings scheme fitted common language better than color experience, overview of the six base colors in Natural Color System with their equivalent in hex triplet, RGB and HSV coordinates systems. However, note that these codes are only approximate, as the definition of NCS elementaries is based on perception, Color chart, other color systems and charts NCS1950 color chart An online NCS calculator
7.
Adobe RGB color space
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The Adobe RGB color space is an RGB color space developed by Adobe Systems, Inc. in 1998. It was designed to encompass most of the colors achievable on CMYK color printers, the Adobe RGB color space encompasses roughly 50% of the visible colors specified by the CIELAB color space – improving upon the gamut of the sRGB color space, primarily in cyan-green hues. Beginning in 1997, Adobe Systems was looking into creating ICC profiles that its consumers could use in conjunction with Photoshops new color management features, since not many applications at the time had any ICC color management, most operating systems did not ship with useful profiles. Lead developer of Photoshop, Thomas Knoll decided to build an ICC profile around specifications he found in the documentation for the SMPTE 240M standard, SMPTE 240Ms gamut was wider than that of the sRGB color space, but not by much. However, with the release of Photoshop 5.0 nearing, the real values were much closer to sRGBs, which avid Photoshop consumers did not enjoy as a working environment. To make matters worse, an engineer had made an error when copying the red primary chromaticity coordinates, in the end, Adobe decided to keep the incorrect profile, but changed the name to Adobe RGB in order to avoid a trademark search or infringement. In Adobe RGB, colors are specified as triplets, where each of the R, G, when displayed on a monitor, the exact chromaticities of the reference white point, the reference black point, and the primaries are specified. Moreover, the point shall have the same chromaticity as the white point. The ambient illumination level at the monitor faceplate when the monitor is turned off must be 32 lx, as with sRGB, the RGB component values in Adobe RGB are not proportional to the luminances. Rather, a gamma of 2.2 is assumed, without the segment near zero that is present in sRGB. The precise gamma value is 563/256, or 2.19921875, in coverage of the CIE1931 color space the Adobe RGB color space covers 52. 1%. Through the application of the 3x3 matrix below, the input images normalized XYZ tristimulus values are transformed into RGB tristimulus values, the component values would be clipped to the range. Since sRGB serves as a best guess metric for how another persons monitor produces color, sRGBs color gamut encompasses just 35% of the visible colors specified by CIE, whereas Adobe RGB encompasses slightly more than 50% of all visible colors. Adobe RGB extends into richer cyans and greens than does sRGB – for all levels of luminance, the two gamuts are often compared in mid-tone values, but clear differences are evident in shadows and highlights as well. In fact, Adobe RGB expands its advantages to areas of intense orange, yellow, also, although Adobe RGB can theoretically represent a wider gamut of colors, the color space requires special software and a complex workflow in order to utilize its full range. Otherwise, the colors would be squeezed into a smaller range in order to match sRGBs more widely used gamut. Color spaces with larger gamuts stretch the bits over a region of colors. A similar, yet not as dramatic concentration of bit depth occurs with Adobe RGB versus sRGB, on the contrary, one may have plenty of spare bits if using a 16-bit image, thus negating any reduction due to the choice of working space
8.
SRGB
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SRGB is the standard RGB color space created cooperatively by HP and Microsoft in 1996 for use on monitors, printers and the Internet, and subsequently standardized by the IEC as IEC 61966-2-1,1999. It is often used as the color space for images that do not contain any color space information. This specification allowed sRGB to be displayed on typical CRT monitors of the time. SRGB defines the chromaticities of the red, green, and blue primaries, the gamut of chromaticities that can be represented in sRGB is the color triangle defined by these primaries. SRGB also defines a transformation between the intensity of these primaries and the actual number stored. The curve is similar to the response of a CRT display. It is more important to replicate this curve than the primaries to get correct display of an sRGB image and this nonlinear conversion means that sRGB is a reasonably efficient use of the values in an integer-based image file to display human-discernible light levels. Unlike most other RGB color spaces, the sRGB gamma cannot be expressed as a numerical value. The overall gamma is approximately 2.2, consisting of a section near black, and a non-linear section elsewhere involving a 2.4 exponent. The purpose of the section is so the curve does not have an infinite slope at zero. The CIE XYZ values must be scaled so that the Y of D65 is 1.0 and this is usually true but some color spaces use 100 or other values. The first step in the calculation of sRGB from CIE XYZ is a linear transformation, = It is important to note that these linear RGB values are not the final result as they have not been adjusted for the gamma correction. SRGB was designed to reflect a typical real-world monitor with a gamma of 2.2, and the following formula transforms the linear RGB values into sRGB. If values in the range 0 to 255 are required, e. g. for video display or 8-bit graphics, the values are usually clipped to the 0 to 1 range. This clipping can be done before or after this gamma calculation, again the sRGB component values R s r g b, G s r g b, B s r g b are in the range 0 to 1. Followed by a multiplication of the linear values to get XYZ, = It is often casually stated that the decoding gamma for sRGB data is 2.2. The transformation was designed to approximate a gamma of about 2.2, but with a portion near zero to avoid having an infinite slope at K =0. The continuity condition for the curve C l i n e a r which is defined above as a function of C s r g b, is γ = K0 ϕ
9.
Color model
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A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components. When this model is associated with a description of how the components are to be interpreted. This section describes ways in which human color vision can be modeled, the origin, =, corresponds to black. White has no position in this diagram, rather it is defined according to the color temperature or white balance as desired or as available from ambient lighting. The human color space is a horse-shoe-shaped cone such as here, extending from the origin to, in principle. The most saturated colors are located at the rim of the region. As far as the responses of the receptors in the eye are concerned, the latter color names refer to orange and white light respectively, with an intensity that is lower than the light from surrounding areas. The black areas have not actually become darker but appear black relative to the higher intensity white projected onto the screen around it, the human tristimulus space has the property that additive mixing of colors corresponds to the adding of vectors in this space. This makes it easy to, for example, describe the colors that can be constructed from the red, green. One of the first mathematically defined color spaces is the CIE XYZ color space and these data were measured for human observers and a 2-degree field of view. In 1964, supplemental data for a 10-degree field of view were published, note that the tabulated sensitivity curves have a certain amount of arbitrariness in them. The shapes of the individual X, Y and Z sensitivity curves can be measured with a reasonable accuracy. However, the luminosity function is subjective, since it involves asking a test person whether two light sources have the same brightness, even if they are in completely different colors. Along the same lines, the magnitudes of the X, Y. One could as well define a color space with an X sensitivity curve that has twice the amplitude. This new color space would have a different shape, the sensitivity curves in the CIE1931 and 1964 xyz color space are scaled to have equal areas under the curves. Because the CIE sensitivity curves have equal areas under the curves, the values for X, Y, and Z are obtained by integrating the product of the spectrum of a light beam and the published color-matching functions. This is called RGB color space, mixtures of light of these primary colors cover a large part of the human color space and thus produce a large part of human color experiences
10.
RGB color model
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The RGB color model is an additive color model in which red, green and blue light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three primary colors, red, green and blue. Before the electronic age, the RGB color model already had a theory behind it. Thus an RGB value does not define the same color across devices without some kind of color management, typical RGB input devices are color TV and video cameras, image scanners, video games, and digital cameras. Typical RGB output devices are TV sets of technologies, computer and mobile phone displays, video projectors, multicolor LED displays. Color printers, on the hand are not RGB devices. This article discusses concepts common to all the different color spaces that use the RGB color model, to form a color with RGB, three light beams must be superimposed. Each of the three beams is called a component of color, and each of them can have an arbitrary intensity, from fully off to fully on. The RGB color model is additive in the sense that the three beams are added together, and their light spectra add, wavelength for wavelength. This is essentially opposite to the color model that applies to paints, inks, dyes. When the intensities for all the components are the same, the result is a shade of gray, darker or lighter depending on the intensity. When the intensities are different, the result is a colorized hue, a secondary color is formed by the sum of two primary colors of equal intensity, cyan is green+blue, magenta is red+blue, and yellow is red+green. The RGB color model itself does not define what is meant by red, green and blue colorimetrically, and so the results of mixing them are not specified as absolute, but relative to the primary colors. When the exact chromaticities of the red, green and blue primaries are defined, the normal three kinds of light-sensitive photoreceptor cells in the human eye respond most to yellow, green, and violet light. As an example, suppose that light in the range of wavelengths enters the eye. Light of these wavelengths would activate both the medium and long wavelength cones of the retina, but not equally—the long-wavelength cells will respond more, the difference in the response can be detected by the brain, and this difference is the basis of our perception of orange. Thus, the appearance of an object results from light from the object entering our eye and stimulating the different cones simultaneously. The first experiments with RGB in early color photography were made in 1861 by Maxwell himself, to reproduce the color photograph, three matching projections over a screen in a dark room were necessary
11.
CMYK color model
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The CMYK color model is a subtractive color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four used in some color printing, cyan, magenta, yellow. Though it varies by print house, press operator, press manufacturer, the K in CMYK stands for key because in four-color printing, cyan, magenta and yellow printing plates are carefully keyed, or aligned, with the key of the black key plate. Some sources suggest that the K in CMYK comes from the last letter in black and was chosen because B already means blue. Some sources claim this explanation, although useful as a mnemonic, is incorrect, the CMYK model works by partially or entirely masking colors on a lighter, usually white, background. The ink reduces the light that would otherwise be reflected, such a model is called subtractive because inks subtract brightness from white. In additive color models such as RGB, white is the combination of all primary colored lights. In the CMYK model, it is the opposite, white is the color of the paper or other background. To save cost on ink, and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of the combination of cyan, magenta, with halftoning, a full continuous range of colors can be produced. To improve print quality and reduce moiré patterns, the screen for each color is set at a different angle. Common reasons for using black ink include, In traditional preparation of color separations, in some cases a black keyline was used when it served as both a color indicator and an outline to be printed in black. Because usually the black plate contained the keyline, the K in CMYK represents the keyline or black plate, also sometimes called the key plate. A combination of 100% cyan, magenta, and yellow inks soaks the paper with ink, making it slower to dry, causing bleeding, adding black ink absorbs more light and yields much better blacks. Using black ink is less expensive than using the corresponding amounts of colored inks. When a very dark area is desirable, a colored or gray CMY bedding is applied first, then a black layer is applied on top, making a rich, deep black. A black made with just CMY inks is sometimes called a composite black, the amount of black to use to replace amounts of the other ink is variable, and the choice depends on the technology, paper and ink in use. Processes called under color removal, under addition, and gray component replacement are used to decide on the final mix. CMYK or process color printing is contrasted with spot color printing, some printing presses are capable of printing with both four-color process inks and additional spot color inks at the same time
12.
Color space
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A color space is a specific organization of colors. In combination with physical device profiling, it allows for reproducible representations of color, for example, Adobe RGB and sRGB are two different absolute color spaces, both based on the RGB color model. When defining a color space, the reference standard is the CIELAB or CIEXYZ color spaces. For example, although several specific color spaces are based on the RGB color model, colors can be created in printing with color spaces based on the CMYK color model, using the subtractive primary colors of pigment. The resulting 3-D space provides a position for every possible color that can be created by combining those three pigments. Colors can be created on computer monitors with color spaces based on the RGB color model, a three-dimensional representation would assign each of the three colors to the X, Y, and Z axes. Note that colors generated on given monitor will be limited by the medium, such as the phosphor or filters. Another way of creating colors on a monitor is with an HSL or HSV color space, based on hue, saturation, with such a space, the variables are assigned to cylindrical coordinates. Many color spaces can be represented as three-dimensional values in this manner, but some have more, or fewer dimensions, Color space conversion is the translation of the representation of a color from one basis to another. The RGB color model is implemented in different ways, depending on the capabilities of the system used, by far the most common general-used incarnation as of 2006 is the 24-bit implementation, with 8 bits, or 256 discrete levels of color per channel. Any color space based on such a 24-bit RGB model is limited to a range of 256×256×256 ≈16.7 million colors. Some implementations use 16 bits per component for 48 bits total and this is especially important when working with wide-gamut color spaces, or when a large number of digital filtering algorithms are used consecutively. The same principle applies for any color space based on the color model. CIE1931 XYZ color space was one of the first attempts to produce a space based on measurements of human color perception. The CIERGB color space is a companion of CIE XYZ. Additional derivatives of CIE XYZ include the CIELUV, CIEUVW, RGB uses additive color mixing, because it describes what kind of light needs to be emitted to produce a given color. RGB stores individual values for red, green and blue, RGBA is RGB with an additional channel, alpha, to indicate transparency. Common color spaces based on the RGB model include sRGB, Adobe RGB, ProPhoto RGB, scRGB, one starts with a white substrate, and uses ink to subtract color from white to create an image
13.
Gamut
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In color reproduction, including computer graphics and photography, the gamut, or color gamut /ˈɡæmət/, is a certain complete subset of colors. The most common refers to the subset of colors which can be accurately represented in a given circumstance. Another sense, less used but not less correct, refers to the complete set of colors found within an image at a given time. In the 1850s, the term was applied to a range of colors or hue, for example by Thomas De Quincey, in color theory, the gamut of a device or process is that portion of the color space that can be represented, or reproduced. When certain colors cannot be expressed within a color model. For example, while pure red can be expressed in the RGB color space, it cannot be expressed in the CMYK color space, a device that is able to reproduce the entire visible color space is an unrealized goal within the engineering of color displays and printing processes. While modern techniques allow increasingly good approximations, the complexity of systems often makes them impractical. While processing an image, the most convenient color model used is the RGB model. Printing the image requires transforming the image from the original RGB color space to the printers CMYK color space, during this process, the colors from the RGB which are out of gamut must be somehow converted to approximate values within the CMYK space gamut. Simply trimming only the colors which are out of gamut to the closest colors in the space would burn the image. There are several algorithms approximating this transformation, but none of them can be truly perfect and this is why identifying the colors in an image which are out of gamut in the target color space as soon as possible during processing is critical for the quality of the final product. Gamuts are commonly represented as areas in the CIE1931 chromaticity diagram as shown at right, the cone drawn in grey corresponds roughly to the CIE diagram at right, with the added dimension of brightness. The axes in these diagrams are the responses of the short-wavelength, middle-wavelength, the other letters indicate black, red, green, blue, cyan, magenta, yellow, and white colors. The exact positions of the apexes depends on the spectra of the phosphors in the computer monitor. The gamut of the CMYK color space is, ideally, approximately the same as that for RGB, with slightly different apexes, depending on both the exact properties of the dyes and the light source. In practice, due to the way raster-printed colors interact with other and the paper and due to their non-ideal absorption spectra. The gamut of colors in nature has a similar, though more rounded. An object that only a narrow band of wavelengths will have a color close to the edge of the CIE diagram
14.
Lab color space
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The Lab color space describes mathematically all perceivable colors in the three dimensions L for lightness and a and b for the color opponents green–red and blue–yellow. Other, less common examples of spaces with Lab representations make use of the CIE1994 color difference. The Lab color space exceeds the gamuts of the RGB and CMYK color models, one of the most important attributes of the Lab model is device independence. This means that the colors are defined independent of their nature of creation or the device they are displayed on, the Lab color space is used when graphics for print have to be converted from RGB to CMYK, as the Lab gamut includes both the RGB and CMYK gamut. Also it is used as an interchange format between different devices as for its device independency, the space itself is a three-dimensional real number space, that contains an infinite number of possible representations of colors. The lightness, L*, represents the darkest black at L* =0, the color channels, a* and b*, will represent true neutral gray values at a* =0 and b* =0. The red/green opponent colors are represented along the a* axis, with green at negative a* values, the yellow/blue opponent colors are represented along the b* axis, with blue at negative b* values and yellow at positive b* values. The scaling and limits of the a* and b* axes will depend on the implementation of Lab color, as described below. Perceptually uniform means that a change of the amount in a color value should produce a change of about the same visual importance. When storing colors in limited precision values, this can improve the reproduction of tones, both Lab spaces are relative to the white point of the XYZ data they were converted from. Lab values do not define absolute colors unless the point is also specified. Often, in practice, the point is assumed to follow a standard and is not explicitly stated. The lightness correlate in CIELAB is calculated using the root of the relative luminance. Unlike the RGB and CMYK color models, Lab color is designed to approximate human vision and it aspires to perceptual uniformity, and its L component closely matches human perception of lightness, although it does not take the Helmholtz–Kohlrausch effect into account. Thus, it can be used to make accurate color balance corrections by modifying output curves in the a and b components, or to adjust the lightness contrast using the L component. In the 1990s, when computer hardware and software were limited to storing and manipulating mostly 8-bit/channel bitmaps, converting an RGB image to Lab, with 16-bit/channel and floating-point support now common, the loss due to quantization is negligible. A big portion of the Lab coordinate space cannot be generated by spectral distributions, it falls outside the human vision. Some specific uses of the abbreviation in software, literature etc, in Adobe Photoshop, image editing using Lab mode is CIELAB D50
15.
RGB color space
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An RGB color space is any additive color space based on the RGB color model. The complete specification of an RGB color space requires a white point chromaticity. As of 2007, sRGB is by far the most commonly used RGB color space, RGB is an abbreviation for red–green–blue. An RGB color space can be understood by thinking of it as all colors that can be made from three colored lights for red, green, and blue. Imagine, for example, shining three lights together onto a wall in a dark room, one red light, one green light. If only the red light is on, the wall will be red, if only the green light is on, the wall will look green. If the red and green lights are on together, the wall will look yellow, dim the red light and the wall will become more of a yellow-green. Dim the green light instead, and the wall will become more orange, bringing up the blue light a bit will cause the orange to become less saturated and more whitish. In all, each setting of the three dimmers will produce a different result, either in color or in brightness or both, the set of all possible results is the gamut defined by those particular color lamps. An LCD display can be thought of as a grid of thousands of red, green. The gamut of the display will depend on the three used for the red, green, and blue lights. A wide-gamut display will have very saturated, pure light colors, RGB is a convenient color model for computer graphics because the human visual system works in a way that is similar – though not quite identical – to an RGB color space. The most commonly used RGB color spaces are sRGB and Adobe RGB, Adobe has recently developed another color space called Adobe Wide Gamut RGB, which is even larger, in detriment to gamut density. As of 2007, sRGB is by far the most commonly used RGB color space, particularly in consumer digital cameras, HD video cameras. HDTVs use a space, commonly called Rec. The sRGB space is considered adequate for most consumer applications, having all devices use the same color space is convenient in that an image does not need to be converted from one color space to another before being displayed. However, sRGBs limited gamut leaves out many highly saturated colors that can be produced by printers or in film, the wider gamut Adobe RGB is being built into more medium-grade digital cameras, and is favored by many professional graphic artists for its larger gamut. RGB spaces are generally specified by defining three primary colors and a white point, in the table below the three primary colors and white points for various RGB spaces are given
16.
Thomas Young (scientist)
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Thomas Young was an English polymath and physician. Young made notable contributions to the fields of vision, light, solid mechanics, energy, physiology, language, musical harmony. He made a number of original and insightful innovations in the decipherment of Egyptian hieroglyphs before Jean-François Champollion eventually expanded on his work and he was mentioned by, among others, William Herschel, Hermann von Helmholtz, James Clerk Maxwell, and Albert Einstein. Young has been described as The Last Man Who Knew Everything, Young belonged to a Quaker family of Milverton, Somerset, where he was born in 1773, the eldest of ten children. At the age of fourteen Young had learned Greek and Latin and was acquainted with French, Italian, Hebrew, German, Aramaic, Syriac, Samaritan, Arabic, Persian, Turkish, in 1797 he entered Emmanuel College, Cambridge. In the same year he inherited the estate of his granduncle, Richard Brocklesby, which made him financially independent, Young published many of his first academic articles anonymously to protect his reputation as a physician. In 1801 Young was appointed professor of philosophy at the Royal Institution. In two years, he delivered 91 lectures, in 1802, he was appointed foreign secretary of the Royal Society, of which he had been elected a fellow in 1794. He resigned his professorship in 1803, fearing that its duties would interfere with his medical practice and his lectures were published in 1807 in the Course of Lectures on Natural Philosophy and contain a number of anticipations of later theories. In 1811 Young became physician to St Georges Hospital, and in 1814 he served on an appointed to consider the dangers involved in the general introduction of gas into London. Young was elected a Foreign Honorary Member of the American Academy of Arts, a few years before his death he became interested in life insurance, and in 1827 he was chosen one of the eight foreign associates of the French Academy of Sciences. In 1828, he was elected a member of the Royal Swedish Academy of Sciences. Thomas Young died in London on 10 May 1829, and was buried in the cemetery of St. Giles Church in Farnborough, Kent, England. Westminster Abbey houses a marble tablet in memory of Young bearing an epitaph by Hudson Gurney, Young was highly regarded by his friends. He was said never to impose his knowledge, but if asked was able to even the most difficult scientific question with ease. Although very learned he had a reputation for sometimes having difficulty in communicating his knowledge and it was said by one of his contemporaries that His words were not those in familiar use, and the arrangement of his ideas seldom the same as those he conversed with. He was therefore worse calculated than any man I ever knew for the communication of knowledge, later scholars and scientists have praised Youngs work although they may know him only through achievements he made in their fields. His contemporary Sir John Herschel called him a truly original genius, Albert Einstein praised him in the 1931 foreword to an edition of Newtons Opticks
17.
Hermann von Helmholtz
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Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions in several scientific fields. The largest German association of institutions, the Helmholtz Association, is named after him. In physics, he is known for his theories on the conservation of energy, work in electrodynamics, chemical thermodynamics, Helmholtzs work is influenced by the philosophy of Johann Gottlieb Fichte and Immanuel Kant. He tried to trace their theories in empirical matters like physiology, as a young man, Helmholtz was interested in natural science, but his father wanted him to study medicine at the Charité because there was financial support for medical students. Trained primarily in physiology, Helmholtz wrote on other topics, ranging from theoretical physics, to the age of the Earth. Helmholtzs first academic position was as a teacher of Anatomy at the Academy of Arts in Berlin in 1848 and he then moved to take a post of associate professor of physiology at the Prussian University of Königsberg, where he was appointed in 1849. In 1855 he accepted a professorship of anatomy and physiology at the University of Bonn. He was not particularly happy in Bonn, however, and three later he transferred to the University of Heidelberg, in Baden, where he served as professor of physiology. In 1871 he accepted his final university position, as professor of physics at the University of Berlin and his first important scientific achievement, an 1847 treatise on the conservation of energy, was written in the context of his medical studies and philosophical background. He discovered the principle of conservation of energy while studying muscle metabolism and he tried to demonstrate that no energy is lost in muscle movement, motivated by the implication that there were no vital forces necessary to move a muscle. This was a rejection of the tradition of Naturphilosophie which was at that time a dominant philosophical paradigm in German physiology. He published his theories in his book Über die Erhaltung der Kraft, in the 1850s and 60s, building on the publications of William Thomson, Helmholtz and William Rankine popularized the idea of the heat death of the universe. In fluid dynamics, Helmholtz made several contributions, including Helmholtzs theorems for vortex dynamics in inviscid fluids, Helmholtz was a pioneer in the scientific study of human vision and audition. He coined the term psychophysics, to capture the distinction between the measurement of physical stimuli and their effect on human perception. The physical sound needs to be increased exponentially in order for equal steps to seem linear, Helmholtz paved the way in experimental studies on the relationship between the physical energy and its appreciation, with the goal in mind to develop psychophysical laws. The sensory physiology of Helmholtz was the basis of the work of Wilhelm Wundt, a student of Helmholtz and he, more explicitly than Helmholtz, described his research as a form of empirical philosophy and as a study of the mind as something separate. Helmholtz had, in his early repudiation of Naturphilosophie, stressed the importance of materialism, in 1851, Helmholtz revolutionized the field of ophthalmology with the invention of the ophthalmoscope, an instrument used to examine the inside of the human eye. Helmholtzs interests at that time were focused on the physiology of the senses
18.
Cone cell
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Cone cells, or cones, are one of three types of photoreceptor cells in the retina of mammalian eyes. They are responsible for vision and function best in relatively bright light, as opposed to rod cells. Cone cells are packed in the fovea centralis, a 0.3 mm diameter rod-free area with very thin. There are about six to seven million cones in an eye and are most concentrated towards the macula. The commonly cited figure of six million cone cells in the eye was found by Osterberg in 1935. Oysters textbook cites work by Curcio et al. indicating a close to 4.5 million cone cells and 90 million rod cells in the human retina. Cones are less sensitive to light than the rod cells in the retina and they are also able to perceive finer detail and more rapid changes in images, because their response times to stimuli are faster than those of rods. Cones are normally one of the three types, each with different pigment, namely, S-cones, M-cones and L-cones, each cone is therefore sensitive to visible wavelengths of light that correspond to short-wavelength, medium-wavelength and long-wavelength light. Being colour blind can change this, and there have been some verified reports of people with four or more types of cones, destruction of the cone cells from disease would result in blindness. Humans normally have three types of cones, the first responds the most to light of long wavelengths, peaking at about 560 nm, this type is sometimes designated L for long. The second type responds the most to light of medium-wavelength, peaking at 530 nm, the third type responds the most to short-wavelength light, peaking at 420 nm, and is designated S for short. The three types have peak wavelengths near 564–580 nm, 534–545 nm, and 420–440 nm, respectively, the difference in the signals received from the three cone types allows the brain to perceive a continuous range of colours, through the opponent process of colour vision. All of the contain the protein photopsin, with variations in its conformation causing differences in the optimum wavelengths absorbed. Similarly, blue and violet hues are perceived when the S receptor is stimulated more, cones are most sensitive to light at wavelengths around 420 nm. People with aphakia, a condition where the eye lacks a lens, at lower light levels, where only the rod cells function, the sensitivity is greatest at a blueish-green wavelength. Separate connectivity is established in the inner plexiform layer so that each connection is parallel, while it has been discovered that there exists a mixed type of bipolar cells that bind to both rod and cone cells, bipolar cells still predominantly receive their input from cone cells. Cone cells are somewhat shorter than rods, but wider and tapered, and are less numerous than rods in most parts of the retina. Structurally, cone cells have a cone-like shape at one end where a pigment filters incoming light, giving them their different response curves
19.
Blue
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Blue is the colour between violet and green on the optical spectrum of visible light. Human eyes perceive blue when observing light with a wavelength between 450 and 495 nanometres, which is between 4500 and 4950 ångströms. Blues with a frequency and thus a shorter wavelength gradually look more violet, while those with a lower frequency. Pure blue, in the middle, has a wavelength of 470 nanometers, in painting and traditional colour theory, blue is one of the three primary colours of pigments, along with red and yellow, which can be mixed to form a wide gamut of colours. Red and blue mixed together form violet, blue and yellow together form green, Blue is also a primary colour in the RGB colour model, used to create all the colours on the screen of a television or computer monitor. The clear sky and the sea appear blue because of an optical effect known as Rayleigh scattering. When sunlight passes through the atmosphere, the wavelengths are scattered more widely by the oxygen and nitrogen molecules. An optical effect called Tyndall scattering, similar to Rayleigh scattering, explains blue eyes, distant objects appear more blue because of another optical effect called atmospheric perspective. Blue has been used for art and decoration since ancient times and it is the most important color in Judaism. In the Middle Ages, cobalt blue was used to colour the stained glass windows of cathedrals, beginning in the 9th century, Chinese artists used cobalt to make fine blue and white porcelain. Blue dyes for clothing were made from woad in Europe and indigo in Asia, in 1828 a synthetic ultramarine pigment was developed, and synthetic blue dyes and pigments gradually replaced mineral pigments and vegetable dyes. Pierre-Auguste Renoir, Vincent van Gogh and other late 19th century painters used ultramarine and cobalt blue not just to depict nature, in the late 18th century and 19th century, blue became a popular colour for military uniforms and police uniforms. In the 20th century, because blue was associated with harmony, it was chosen as the colour of the flags of the United Nations. Surveys in the US and Europe show that blue is the colour most commonly associated with harmony, faithfulness, confidence, distance, infinity, the imagination, cold, and sometimes with sadness. In US and European public opinion polls it is the most popular colour, Blue is the colour of light between violet and green on the visible spectrum. Blues also vary in shade or tint, darker shades of blue contain black or grey, darker shades of blue include ultramarine, cobalt blue, navy blue, and Prussian blue, while lighter tints include sky blue, azure, and Egyptian blue. Today most blue pigments and dyes are made by a chemical process, the modern English word blue comes from Middle English bleu or blewe, from the Old French bleu, a word of Germanic origin, related to the Old High German word blao. In heraldry, the azure is used for blue
20.
Green
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Green is the color between blue and yellow on the spectrum of visible light. It is evoked by light with a predominant wavelength of roughly 495–570 nm, the modern English word green comes from the Middle English and Anglo-Saxon word grene, from the same Germanic root as the words grass and grow. It is the color of living grass and leaves and as a result is the color most associated with springtime, growth, 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 environments by taking on a green hue themselves as camouflage. Several minerals have a color, including the emerald, which is colored green by its chromium content. In surveys made in Europe and the United States, green is the color most commonly associated with nature, life, health, youth, spring, hope and envy. In Europe and the U. S. green is associated with death, sickness, or the devil. In the Middle Ages and Renaissance, when the color of clothing showed the social status, green was worn by merchants, bankers. The Mona Lisa by Leonardo da Vinci wears green, showing she is not from a noble family, Green is also the traditional color of safety and permission, a green light means go ahead, a green card permits permanent residence in the United States. It is the most important color in Islam and it was the color of the banner of Muhammad, and is found in the flags of nearly all Islamic countries, and represents the lush vegetation of Paradise. It is also associated with the culture of Gaelic Ireland. 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 campaigns in advertising, as companies have sold green, or environmentally friendly. The word green comes from the Middle English and Old English word grene, which, like the German word grün, has the same root as the words grass and grow. It is from a Common Germanic *gronja-, which is reflected in Old Norse grænn, Old High German gruoni, ultimately from a PIE root *ghre- to grow. The first recorded use of the word as a term in Old English dates to ca. Latin with viridis also has a genuine and widely 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. Likewise the Slavic languages with zelenъ, Ancient Greek also had a term for yellowish, pale green – χλωρός, chloros, cognate with χλοερός verdant and χλόη the green of new growth
21.
Red
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Red is the color at the longer-wavelengths end of the spectrum of visible light next to orange, at the opposite end from violet. Red color has a predominant light wavelength of roughly 620–740 nanometers, light with a longer wavelength than red but shorter than terahertz radiation and microwave is called infrared. Red is one of the secondary colors, resulting from the combination of yellow. Traditionally, it was viewed as a primary colour, along with yellow and blue, in the RYB color space and traditional color wheel formerly used by painters. Reds can vary in shade from light pink to very dark maroon or burgundy. Red is the color of cyan. In nature, the red color of blood comes from hemoglobin, the red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide. It also causes the red color of the planet Mars, the color of autumn leaves is caused by pigments called anthocyanins, which are produced towards the end of summer, when the green chlorophyll is no longer produced. One to two percent of the population has red hair, the color is produced by high levels of the reddish pigment pheomelanin. Since red is the color of blood, it has historically been associated with sacrifice, danger, modern surveys in the United States and Europe show red is also the color most commonly associated with heat, activity, passion, sexuality, anger, love and joy. In China, India and many other Asian countries it is the color of symbolizing happiness, since the 19th century, red has also been associated with socialism and communism. The word red is derived from the Old English rēad, the word can be further traced to the Proto-Germanic rauthaz and the Proto-Indo European root rewdʰ-. In Sanskrit, the word means red or blood. In the Akkadian language of Ancient Mesopotamia and in the modern Inuit language of Inuit, the words for colored in Latin and Spanish both also mean red. In Portuguese the word for red is vermelho, which comes from Latin vermiculus, in the Russian language, the word for red, Кра́сный, comes from the same old Slavic root as the words for beautiful—красивый and excellent—прекрасный. Thus Red Square in Moscow, named long before the Russian Revolution, in heraldry, the word gules is used for red. Red can vary in hue from orange-red to violet-red, and for each hue there is a variety of shades and tints. Red hematite powder was found scattered around the remains at a grave site in a Zhoukoudian cave complex near Beijing
22.
Brain
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The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. The brain is located in the head, usually close to the organs for senses such as vision. The brain is the most complex organ in a vertebrates body, in a human, the cerebral cortex contains approximately 15–33 billion neurons, each connected by synapses to several thousand other neurons. Physiologically, the function of the brain is to exert centralized control over the other organs of the body, the brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment, the operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. This article compares the properties of brains across the range of animal species. It deals with the human brain insofar as it shares the properties of other brains, the ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because more can be said about them in a human context. The most important is brain disease and the effects of brain damage, the shape and size of the brain varies greatly between species, and identifying common features is often difficult. Nevertheless, there are a number of principles of architecture that apply across a wide range of species. Some aspects of structure are common to almost the entire range of animal species, others distinguish advanced brains from more primitive ones. The simplest way to gain information about brain anatomy is by visual inspection, Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the consists of areas of so-called grey matter, with a dark color, separated by areas of white matter. Further information can be gained by staining slices of tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, the brains of all species are composed primarily of two broad classes of cells, neurons and glial cells. Glial cells come in types, and perform a number of critical functions, including structural support, metabolic support, insulation. Neurons, however, are considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to target cells over long distances
23.
Hermann Grassmann
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Hermann Günther Grassmann was a German polymath, known in his day as a linguist and now also as a mathematician. He was also a physicist, neohumanist, general scholar, and his mathematical work was little noted until he was in his sixties. Grassmann was the third of 12 children of Justus Günter Grassmann, a minister who taught mathematics and physics at the Stettin Gymnasium. Grassmann was a student until he obtained a high mark on the examinations for admission to Prussian universities. Beginning in 1827, he studied theology at the University of Berlin, also taking classes in languages, philosophy. He does not appear to have courses in mathematics or physics. Although lacking university training in mathematics, it was the field that most interested him when he returned to Stettin in 1830 after completing his studies in Berlin. After a year of preparation, he sat the examinations needed to teach mathematics in a gymnasium, around this time, he made his first significant mathematical discoveries, ones that led him to the important ideas he set out in his 1844 paper referred to as A1. In 1834 Grassmann began teaching mathematics at the Gewerbeschule in Berlin, a year later, he returned to Stettin to teach mathematics, physics, German, Latin, and religious studies at a new school, the Otto Schule. Over the next four years, Grassmann passed examinations enabling him to mathematics, physics, chemistry. In 1847, he was made an Oberlehrer or head teacher, in 1852, he was appointed to his late fathers position at the Stettin Gymnasium, thereby acquiring the title of Professor. In 1847, he asked the Prussian Ministry of Education to be considered for a university position, whereupon that Ministry asked Kummer for his opinion of Grassmann, Kummer wrote back saying that Grassmanns 1846 prize essay contained. Commendably good material expressed in a deficient form, kummers report ended any chance that Grassmann might obtain a university post. This episode proved the norm, time and again, leading figures of Grassmanns day failed to recognize the value of his mathematics, after writing a series of articles on constitutional law, Hermann parted company with the newspaper, finding himself increasingly at odds with its political direction. Grassmann had eleven children, seven of whom reached adulthood, a son, Hermann Ernst Grassmann, became a professor of mathematics at the University of Giessen. One of the examinations for which Grassmann sat required that he submit an essay on the theory of the tides. This essay, first published in the Collected Works of 1894–1911, contains the first known appearance of what are now called linear algebra and he went on to develop those methods in his A1 and A2. Since A1 proposed a new foundation for all of mathematics, the work began with general definitions of a philosophical nature
24.
Vector space
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A vector space is a collection of objects called vectors, which may be added together and multiplied by numbers, called scalars in this context. Scalars are often taken to be numbers, but there are also vector spaces with scalar multiplication by complex numbers, rational numbers. The operations of addition and scalar multiplication must satisfy certain requirements, called axioms. Euclidean vectors are an example of a vector space and they represent physical quantities such as forces, any two forces can be added to yield a third, and the multiplication of a force vector by a real multiplier is another force vector. In the same vein, but in a more geometric sense, Vector spaces are the subject of linear algebra and are well characterized by their dimension, which, roughly speaking, specifies the number of independent directions in the space. Infinite-dimensional vector spaces arise naturally in mathematical analysis, as function spaces and these vector spaces are generally endowed with additional structure, which may be a topology, allowing the consideration of issues of proximity and continuity. Among these topologies, those that are defined by a norm or inner product are commonly used. This is particularly the case of Banach spaces and Hilbert spaces, historically, the first ideas leading to vector spaces can be traced back as far as the 17th centurys analytic geometry, matrices, systems of linear equations, and Euclidean vectors. Today, vector spaces are applied throughout mathematics, science and engineering, furthermore, vector spaces furnish an abstract, coordinate-free way of dealing with geometrical and physical objects such as tensors. This in turn allows the examination of local properties of manifolds by linearization techniques, Vector spaces may be generalized in several ways, leading to more advanced notions in geometry and abstract algebra. The concept of space will first be explained by describing two particular examples, The first example of a vector space consists of arrows in a fixed plane. This is used in physics to describe forces or velocities, given any two such arrows, v and w, the parallelogram spanned by these two arrows contains one diagonal arrow that starts at the origin, too. This new arrow is called the sum of the two arrows and is denoted v + w, when a is negative, av is defined as the arrow pointing in the opposite direction, instead. Such a pair is written as, the sum of two such pairs and multiplication of a pair with a number is defined as follows, + = and a =. The first example above reduces to one if the arrows are represented by the pair of Cartesian coordinates of their end points. A vector space over a field F is a set V together with two operations that satisfy the eight axioms listed below, elements of V are commonly called vectors. Elements of F are commonly called scalars, the second operation, called scalar multiplication takes any scalar a and any vector v and gives another vector av. In this article, vectors are represented in boldface to distinguish them from scalars
25.
Linear space
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A vector space is a collection of objects called vectors, which may be added together and multiplied by numbers, called scalars in this context. Scalars are often taken to be numbers, but there are also vector spaces with scalar multiplication by complex numbers, rational numbers. The operations of addition and scalar multiplication must satisfy certain requirements, called axioms. Euclidean vectors are an example of a vector space and they represent physical quantities such as forces, any two forces can be added to yield a third, and the multiplication of a force vector by a real multiplier is another force vector. In the same vein, but in a more geometric sense, Vector spaces are the subject of linear algebra and are well characterized by their dimension, which, roughly speaking, specifies the number of independent directions in the space. Infinite-dimensional vector spaces arise naturally in mathematical analysis, as function spaces and these vector spaces are generally endowed with additional structure, which may be a topology, allowing the consideration of issues of proximity and continuity. Among these topologies, those that are defined by a norm or inner product are commonly used. This is particularly the case of Banach spaces and Hilbert spaces, historically, the first ideas leading to vector spaces can be traced back as far as the 17th centurys analytic geometry, matrices, systems of linear equations, and Euclidean vectors. Today, vector spaces are applied throughout mathematics, science and engineering, furthermore, vector spaces furnish an abstract, coordinate-free way of dealing with geometrical and physical objects such as tensors. This in turn allows the examination of local properties of manifolds by linearization techniques, Vector spaces may be generalized in several ways, leading to more advanced notions in geometry and abstract algebra. The concept of space will first be explained by describing two particular examples, The first example of a vector space consists of arrows in a fixed plane. This is used in physics to describe forces or velocities, given any two such arrows, v and w, the parallelogram spanned by these two arrows contains one diagonal arrow that starts at the origin, too. This new arrow is called the sum of the two arrows and is denoted v + w, when a is negative, av is defined as the arrow pointing in the opposite direction, instead. Such a pair is written as, the sum of two such pairs and multiplication of a pair with a number is defined as follows, + = and a =. The first example above reduces to one if the arrows are represented by the pair of Cartesian coordinates of their end points. A vector space over a field F is a set V together with two operations that satisfy the eight axioms listed below, elements of V are commonly called vectors. Elements of F are commonly called scalars, the second operation, called scalar multiplication takes any scalar a and any vector v and gives another vector av. In this article, vectors are represented in boldface to distinguish them from scalars
26.
Hermann Weyl
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Hermann Klaus Hugo Weyl, ForMemRS was a German mathematician, theoretical physicist and philosopher. His research has had significance for theoretical physics as well as purely mathematical disciplines including number theory. He was one of the most influential mathematicians of the century. Weyl published technical and some works on space, time, matter, philosophy, logic, symmetry. He was one of the first to conceive of combining general relativity with the laws of electromagnetism, while no mathematician of his generation aspired to the universalism of Henri Poincaré or Hilbert, Weyl came as close as anyone. Michael Atiyah, in particular, has commented that whenever he examined a mathematical topic, Weyl was born in Elmshorn, a small town near Hamburg, in Germany, and attended the gymnasium Christianeum in Altona. From 1904 to 1908 he studied mathematics and physics in both Göttingen and Munich and his doctorate was awarded at the University of Göttingen under the supervision of David Hilbert whom he greatly admired. In September 1913 in Göttingen, Weyl married Friederike Bertha Helene Joseph who went by the name Helene, Helene was a daughter of Dr. Bruno Joseph, a physician who held the position of Sanitätsrat in Ribnitz-Damgarten, Germany. Helene was a philosopher and also a translator of Spanish literature into German and it was through Helenes close connection with Husserl that Hermann became familiar with Husserls thought. Hermann and Helene had two sons, Fritz Joachim Weyl and Michael Weyl, both of whom were born in Zürich, Switzerland, Helene died in Princeton, New Jersey on September 5,1948. A memorial service in her honor was held in Princeton on September 9,1948, speakers at her memorial service included her son Fritz Joachim Weyl and mathematicians Oswald Veblen and Richard Courant. In 1950 Hermann married sculptress Ellen Bär, who was the widow of professor Richard Josef Bär of Zürich, einstein had a lasting influence on Weyl, who became fascinated by mathematical physics. In 1921 Weyl met Erwin Schrödinger, a theoretical physicist who at the time was a professor at the University of Zürich and they were to become close friends over time. Weyl left Zürich in 1930 to become Hilberts successor at Göttingen, leaving when the Nazis assumed power in 1933, particularly as his wife was Jewish. He had been offered one of the first faculty positions at the new Institute for Advanced Study in Princeton, New Jersey, as the political situation in Germany grew worse, he changed his mind and accepted when offered the position again. He remained there until his retirement in 1951, together with his second wife Ellen, he spent his time in Princeton and Zürich, and died from a heart attack on December 8,1955 while living in Zürich. Hermann Weyl was cremated in Zurich on December 12,1955 and his cremains remained in private hands until 1999, at which time they were interred in an outdoor columbarium vault in the Princeton Cemetery, located at 29 Greenview Avenue, Princeton, New Jersey. The remains of Hermanns son Michael Weyl are interred next to Hermanns ashes in the same columbarium vault in the Princeton Cemetery
27.
Giuseppe Peano
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Giuseppe Peano was an Italian mathematician. The author of over 200 books and papers, he was a founder of mathematical logic and set theory, the standard axiomatization of the natural numbers is named the Peano axioms in his honor. As part of effort, he made key contributions to the modern rigorous. He spent most of his career teaching mathematics at the University of Turin, Peano was born and raised on a farm at Spinetta, a hamlet now belonging to Cuneo, Piedmont, Italy. Due to Genocchis poor health, Peano took over the teaching of calculus course within two years and his first major work, a textbook on calculus, was published in 1884 and was credited to Genocchi. A few years later, Peano published his first book dealing with mathematical logic, here the modern symbols for the union and intersection of sets appeared for the first time. In 1887, Peano married Carola Crosio, the daughter of the Turin-based painter Luigi Crosio, in 1886, he began teaching concurrently at the Royal Military Academy, and was promoted to Professor First Class in 1889. The next year, the University of Turin also granted him his full professorship, Peanos famous space-filling curve appeared in 1890 as a counterexample. He used it to show that a continuous curve cannot always be enclosed in a small region. This was an example of what came to be known as a fractal. In 1890 Peano founded the journal Rivista di Matematica, which published its first issue in January 1891, in 1891 Peano started the Formulario Project. It was to be an Encyclopedia of Mathematics, containing all known formulae, in 1897, the first International Congress of Mathematicians was held in Zürich. Peano was a key participant, presenting a paper on mathematical logic and he also started to become increasingly occupied with Formulario to the detriment of his other work. In 1898 he presented a note to the Academy about binary numeration and he also became so frustrated with publishing delays that he purchased a printing press. Paris was the venue for the Second International Congress of Mathematicians in 1900, the conference was preceded by the First International Conference of Philosophy where Peano was a member of the patronage committee. He presented a paper which posed the question of correctly formed definitions in mathematics and this became one of Peanos main philosophical interests for the rest of his life. At the conference Peano met Bertrand Russell and gave him a copy of Formulario, Russell was so struck by Peanos innovative logical symbols that he left the conference and returned home to study Peanos text. Peanos students Mario Pieri and Alessandro Padoa had papers presented at the congress also
28.
Printing
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Printing is a process for reproducing text and images using a master form or template. The earliest examples include Cylinder seals and other such as the Cyrus Cylinder. The earliest known form of printing came from China dating to before 220 A. D. Later developments in printing include the type, first developed by Bi Sheng in China around 1040 AD. Johannes Gutenberg introduced mechanical movable type printing to Europe in the 15th century, modern large-scale printing is typically done using a printing press, while small-scale printing is done free-form with a digital printer. Though paper is the most common material, it is frequently done on metals, plastics, cloth. On paper it is carried out as a large-scale industrial process and is an essential part of publishing. Woodblock printing is a technique for printing text, images or patterns that was used widely throughout East Asia and it originated in China in antiquity as a method of printing on textiles and later on paper. As a method of printing on cloth, the earliest surviving examples from China date to before 220 A. D, the earliest surviving woodblock printed fragments are from China. They are of silk printed with flowers in three colours from the Han Dynasty and they are the earliest example of woodblock printing on paper appeared in the mid-seventh century in China. By the ninth century, printing on paper had taken off, by the tenth century,400,000 copies of some sutras and pictures were printed, and the Confucian classics were in print. A skilled printer could print up to 2,000 double-page sheets per day, Printing spread early to Korea and Japan, which also used Chinese logograms, but the technique was also used in Turpan and Vietnam using a number of other scripts. This technique then spread to Persia and Russia and this technique was transmitted to Europe via the Islamic world, and by around 1400 was being used on paper for old master prints and playing cards. However, Arabs never used this to print the Quran because of the limits imposed by Islamic doctrine, block printing, called tarsh in Arabic developed in Arabic Egypt during the ninth-tenth centuries, mostly for prayers and amulets. There is some evidence to suggest that these print blocks made from non-wood materials, possibly tin, lead, the techniques employed are uncertain, however, and they appear to have had very little influence outside of the Muslim world. Though Europe adopted woodblock printing from the Muslim world, initially for fabric, block printing later went out of use in Islamic Central Asia after movable type printing was introduced from China. Block printing first came to Europe as a method for printing on cloth, images printed on cloth for religious purposes could be quite large and elaborate. When paper became relatively easily available, around 1400, the medium transferred very quickly to small religious images
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Primary color
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A set of primary colors is a small, arbitrary set of pigmented physical media, lights or purely abstract elements of a mathematical colorspace model. Distinct colors from a larger gamut can be specified in terms of a mixture of colors which facilitates technological applications such as painting, electronic displays. Any small set of pigments or lights are imperfect physical primary colors in that they cannot be mixed to yield all possible colors that can be perceived by the color vision system. In an additive set of colors, as in coincident projected lights or in electronic visual displays, in a subtractive set of colors, as in mixing of pigments or dyes for printing, the colors magenta, yellow and cyan are normally used. See RGB color model, and CMYK color model for more on these sets of primary colors. Primary colors are not a property of light but are related to the color vision system in animals. The human eye normally contains three types of color photoreceptors that are associated with specialized cone cells. Each photoreceptor responds to different ranges of the electromagnetic spectrum. Humans and other species with three types of color photoreceptor are known as trichromats. Color appearance models like CIECAM02 describe color more generally in six dimensions, most placental mammals other than primates have only two types of color photoreceptor and are therefore dichromats while birds and marsupials are tetrachromats with four color photoreceptor types. There is no peer reviewed scholarly work that has confirmed the existence of a functional human tetrachromat though they are suspected to exist. Demonstrating improved spectral discrimination in any animal can be difficult since complex sets of neurons affect color perception in ways that are difficult to interrogate. Before the nature of colorimetry and visual physiology were well understood a number of color models assigned primary colors to different hues. Young originally proposed red, green and violet, and Maxwell changed violet to blue, Helmholtz proposed a slightly red, a vegetation-green, slightly yellowish. In modern understanding, human cells do not correspond precisely to a specific set of primary colors. There are hundreds of available pigments for visual artists to use. A common approach is to use just a palette of pigments that can be physically mixed to any color that the artist desires in the final work. Contemporary classical realists have often advocated that a palette of white, red, yellow
30.
Pigment
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A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, many materials selectively absorb certain wavelengths of light. Materials that humans have chosen and developed for use as pigments usually have properties that make them ideal for coloring other materials. A pigment must have a high tinting strength relative to the materials it colors and it must be stable in solid form at ambient temperatures. For industrial applications, as well as in the arts, permanence, pigments that are not permanent are called fugitive. Fugitive pigments fade over time, or with exposure to light, pigments are used for coloring paint, ink, plastic, fabric, cosmetics, food, and other materials. Most pigments used in manufacturing and the arts are dry colorants. This powder is added to a binder, a neutral or colorless material that suspends the pigment. A distinction is made between a pigment, which is insoluble in its vehicle, and a dye, which either is itself a liquid or is soluble in its vehicle. A colorant can act as either a pigment or a dye depending on the vehicle involved, in some cases, a pigment can be manufactured from a dye by precipitating a soluble dye with a metallic salt. The resulting pigment is called a lake pigment, the term biological pigment is used for all colored substances independent of their solubility. In 2006, around 7.4 million tons of inorganic, organic, asia has the highest rate on a quantity basis followed by Europe and North America. By 2020, revenues will have risen to approx, the global demand on pigments was roughly US$20.5 billion in 2009, around 1. 5-2% up from the previous year. It is predicted to increase in a growth rate in the coming years. The worldwide sales are said to increase up to US$24.5 billion in 2015, pigments appear the colors they are because they selectively reflect and absorb certain wavelengths of visible light. White light is an equal mixture of the entire spectrum of visible light with a wavelength in a range from about 375 or 400 nanometers to about 760 or 780 nm. When this light encounters a pigment, parts of the spectrum are absorbed by the molecules or ions of the pigment, in organic pigments such as diazo or phthalocyanine compounds the light is absorbed by the conjugated systems of double bonds in the molecule. Some of the inorganic pigments such as vermilion or cadmium yellow absorb light by transferring an electron from the ion to the positive ion
31.
Cyan
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It is evoked by light with a predominant wavelength of between 490–520 nm, between the wavelengths of blue and green. 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 colors, along with magenta, yellow. In the additive color system, or RGB color model, used to all the colors on a computer or television display, cyan is made by mixing equal amounts of green. Cyan is the complement of red, it can be made by the removal of red from white light, 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, turquoise, electric blue, aquamarine, and others described as blue-green. Its name is derived from the Ancient Greek κύανος, transliterated kyanos, meaning blue, dark blue enamel. It was formerly known as blue or cyan-blue, and its first recorded use as a color name in English was in 1879. Further origins of the name can be traced back to a dye produced from the cornflower. In most languages, cyan is not a color term. Reasons for why cyan is not linguistically acknowledged as a 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 color in the RGB color model. In X11 colors, this color is called both cyan and aqua, in the HTML color list, this same color is called aqua. The web colors are more vivid than the used in the CMYK color system. To reproduce the web color cyan in inks, it is necessary to add some white ink to the printers cyan below, so when it is reproduced in printing, it is not a primary subtractive color. It is called aqua because it is a commonly associated with water. Cyan is also one of the inks used in four-color printing, along with magenta, yellow, and black. While both the secondary and the subtractive primary are called cyan, they can be substantially different from one another. Cyan printing ink can be saturated or less saturated than the RGB secondary cyan, depending on what RGB color space
32.
Magenta
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Magenta is a color that is variously defined as purplish-red, reddish-purple, or mauvish-crimson. On computer screens, it is made by mixing equal amounts of blue, on color wheels of the RGB and CMY color models, it is located midway between red and blue. It is the color of green. It is one of the four colors of ink used in printing and by an inkjet printer, along with cyan, yellow. The tone of magenta used in printing is called printers magenta, Magenta was first introduced as the color of a new aniline dye called fuchsine, patented in 1859 by the French chemist François-Emmanuel Verguin. Its name was changed the year to magenta, to celebrate a victory of the French and Sardinian army at the Battle of Magenta on June 4,1859. The web color magenta is called fuchsia. Magenta is a color, meaning that it is not found in the visible spectrum of light. 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 all the colors on a television or computer display, magenta is a secondary color, made by combining equal amounts of red. In this system, magenta is the color of green. In the CMYK color model, used in 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, cyan, and yellow are printed on top of each other on a page, in this model, magenta is the complementary color of green, and these two colors have the highest contrast and the greatest harmony. If combined, green 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 theory, magenta is evoked by light having less power in green wavelengths than in blue/violet. In the Munsell color system, magenta is called red–purple, if the spectrum is wrapped to form a color wheel, magenta appears midway between red and violet. Violet and red, the two components of magenta, are at opposite ends of the spectrum and have very different wavelengths. The additive secondary color magenta, as noted above, is made by combining violet and red light at equal intensity, in optics, fuchsia and magenta are essentially the same color
33.
Yellow
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Yellow is the color between green and orange on the spectrum of visible light. It is evoked by light with a predominant wavelength of roughly 570–590 nm, in traditional color theory, used in painting, and in the subtractive color system, used in color printing, yellow is a primary color. In the RGB color model, used to create colors on television and computer screens, yellow is made by combining red, the word yellow comes from the Old English geolu, geolwe, meaning yellow, yellowish, derived from the Proto-Germanic word gelwaz yellow. It has the same Indo-European base, gʰel-, as the gold and yell. In Iran it has connotations of pallor/sickness, but also wisdom and it plays an important role in Asian culture, particularly in China, where it is seen as the color of happiness, glory, wisdom, harmony, and culture. The word yellow comes from the Old English geolu, geolwe, meaning yellow, yellowish and it has the same Indo-European base, gʰel-, as the words gold and yell, gʰel- means both bright and gleaming, and to cry out. The English term is related to other Germanic words for yellow, namely Scots yella, East Frisian jeel, West Frisian giel, Dutch geel, German gelb, and Swedish and Norwegian gul. According to the Oxford English Dictionary, the oldest known use of word in English is from The Epinal Glossary in 700. Yellow, in the form of yellow pigment made from clay, was one of the first colors used in prehistoric cave art. The cave of Lascaux has an image of a horse colored with yellow estimated to be 17,300 years old, in Ancient Egypt, yellow was associated with gold, which was considered to be imperishable, eternal and indestructible. The skin and bones of the gods were believed to be made of gold, the Egyptians used yellow extensively in tomb paintings, they usually used either yellow ochre or the brilliant orpiment, though it was made of arsenic and was highly toxic. A small paintbox with orpiment pigment was found in the tomb of King Tutankhamun, men were always shown with brown faces, women with yellow ochre or gold faces. The ancient Romans used yellow in their paintings to represent gold and it is found frequently in the murals of Pompeii. During the Post-Classical period, yellow became firmly established as the color of Judas Iscariot, from this connection, yellow also took on associations with envy, jealousy and duplicity. The tradition started in the Renaissance of marking non-Christian outsiders, such as Jews, in 16th century Spain, those accused of heresy and who refused to renounce their views were compelled to come before the Spanish Inquisition dressed in a yellow cape. The color yellow has been associated with moneylenders and finance. The National Pawnbrokers Associations logo depicts three golden spheres hanging from a bar, referencing the three bags of gold that the saint of pawnbroking, St. Nicholas, holds in his hands. Additionally, the symbol of three golden orbs is found in the coat of arms of the House of Medici, a fifteenth century Italian dynasty of bankers and lenders
34.
Black
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Black is the darkest color resulting from the absence or complete absorption of light. Like white and grey, it is a color, literally a color without hue. It is one of the four colors in the CMYK color model, along with cyan, yellow. Black is often used to represent darkness, it is the symbolic opposite of white, Black was one of the first colors used by artists in neolithic cave paintings. In the 14th century, it began to be worn by royalty and it became the color worn by English romantic poets, businessmen and statesmen in the 19th century, and a high fashion color in the 20th century. In the Roman Empire, it became the color of mourning, according to surveys in Europe and North America, it is the color most commonly associated with mourning, the end, secrets, magic, force, violence, evil, and elegance. More distant cognates include Latin flagrare, and Ancient Greek phlegein, the Ancient Greeks sometimes used the same word to name different colors, if they had the same intensity. Kuanos could mean both dark blue and black, the Ancient Romans had two words for black, ater was a flat, dull black, while niger was a brilliant, saturated black. Ater has vanished from the vocabulary, but niger was the source of the country name Nigeria the English word Negro, old High German also had two words for black, swartz for dull black and blach for a luminous black. These are parallelled in Middle English by the terms swart for dull black, swart still survives as the word swarthy, while blaek became the modern English black. In heraldry, the used for the black color is sable, named for the black fur of the sable. Black was one of the first colors used in art, the Lascaux Cave in France contains drawings of bulls and other animals drawn by paleolithic artists between 18,000 and 17,000 years ago. They began by using charcoal, and then made more vivid black pigments by burning bones or grinding a powder of manganese oxide, for the ancient Egyptians, black had positive associations, being the color of fertility and the rich black soil flooded by the Nile. It was the color of Anubis, the god of the underworld, who took the form of a black jackal, and offered protection against evil to the dead. For the ancient Greeks, black was also the color of the underworld, separated from the world of the living by the river Acheron and those who had committed the worst sins were sent to Tartarus, the deepest and darkest level. In the center was the palace of Hades, the king of the underworld, Black was one of the most important colors used by ancient Greek artists. In the 6th century BC, they began making pottery and later red figure pottery. In black-figure pottery, the artist would paint figures with a clay slip on a red clay pot
35.
Coordinate axis
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The order of the coordinates is significant, and they are sometimes identified by their position in an ordered tuple and sometimes by a letter, as in the x-coordinate. The coordinates are taken to be real numbers in elementary mathematics, the use of a coordinate system allows problems in geometry to be translated into problems about numbers and vice versa, this is the basis of analytic geometry. The simplest example of a system is the identification of points on a line with real numbers using the number line. In this system, an arbitrary point O is chosen on a given line. The coordinate of a point P is defined as the distance from O to P. Each point is given a unique coordinate and each number is the coordinate of a unique point. The prototypical example of a system is the Cartesian coordinate system. In the plane, two lines are chosen and the coordinates of a point are taken to be the signed distances to the lines. In three dimensions, three perpendicular planes are chosen and the three coordinates of a point are the distances to each of the planes. This can be generalized to create n coordinates for any point in n-dimensional Euclidean space, depending on the direction and order of the coordinate axis the system may be a right-hand or a left-hand system. This is one of many coordinate systems, another common coordinate system for the plane is the polar coordinate system. A point is chosen as the pole and a ray from this point is taken as the polar axis, for a given angle θ, there is a single line through the pole whose angle with the polar axis is θ. Then there is a point on this line whose signed distance from the origin is r for given number r. For a given pair of coordinates there is a single point, for example, and are all polar coordinates for the same point. The pole is represented by for any value of θ, there are two common methods for extending the polar coordinate system to three dimensions. In the cylindrical coordinate system, a z-coordinate with the meaning as in Cartesian coordinates is added to the r and θ polar coordinates giving a triple. Spherical coordinates take this a further by converting the pair of cylindrical coordinates to polar coordinates giving a triple. A point in the plane may be represented in coordinates by a triple where x/z and y/z are the Cartesian coordinates of the point
36.
Computer monitor
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A computer monitor or a computer display is an electronic visual display for computers. A monitor usually comprises the display device, circuitry, casing, the display device in modern monitors is typically a thin film transistor liquid crystal display or a flat panel LED display, while older monitors used a cathode ray tubes. It can be connected to the computer via VGA, DVI, HDMI, DisplayPort, Thunderbolt, LVDS or other proprietary connectors, originally, computer monitors were used for data processing while television receivers were used for entertainment. From the 1980s onwards, computers have used for both data processing and entertainment, while televisions have implemented some computer functionality. The common aspect ratio of televisions, and computer monitors, has changed from 4,3 to 16,10, to 16,9. Early electronic computers were fitted with a panel of light bulbs where the state of each particular bulb would indicate the state of a particular register bit inside the computer. This allowed the operating the computer to monitor the internal state of the machine. As early monitors were only capable of displaying a limited amount of information. Instead, a printer was the primary output device, while the monitor was limited to keeping track of the programs operation. Multiple technologies have used for computer monitors. Until the 21st century most used cathode ray tubes but they have largely superseded by LCD monitors. The first computer monitors used cathode ray tubes, high-resolution CRT displays were developed for specialized military, industrial and scientific applications but they were far too costly for general use. Either computer could be connected to the terminals of an ordinary color TV set or used with a purpose-made CRT color monitor for optimum resolution. In 1984 IBM introduced the Enhanced Graphics Adapter which was capable of producing 16 colors and had a resolution of 640 x 350, by the end of the 1980s color CRT monitors that could clearly display 1024 x 768 pixels were widely available and increasingly affordable. During the following decade maximum display resolutions gradually increased and prices continued to fall, CRT technology remained dominant in the PC monitor market into the new millennium partly because it was cheaper to produce and offered viewing angles close to 180 degrees. CRTs still offer some image quality advantages over LCDs but improvements to the latter have made much less obvious. There are multiple technologies that have used to implement liquid crystal displays. Commonly, the laptop would be offered with an assortment of display options at increasing price points, monochrome
37.
Cathode ray tube
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The cathode ray tube is a vacuum tube that contains one or more electron guns and a phosphorescent screen, and is used to display images. It modulates, accelerates, and deflects electron beam onto the screen to create the images, the images may represent electrical waveforms, pictures, radar targets, or others. CRTs have also used as memory devices, in which case the visible light emitted from the fluorescent material is not intended to have significant meaning to a visual observer. In television sets and computer monitors, the front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster. An image is produced by controlling the intensity of each of the three beams, one for each additive primary color with a video signal as a reference. A CRT is constructed from an envelope which is large, deep, fairly heavy. The interior of a CRT is evacuated to approximately 0.01 Pa to 133 nPa. evacuation being necessary to facilitate the flight of electrons from the gun to the tubes face. That it is evacuated makes handling an intact CRT potentially dangerous due to the risk of breaking the tube and causing a violent implosion that can hurl shards of glass at great velocity. As a matter of safety, the face is made of thick lead glass so as to be highly shatter-resistant and to block most X-ray emissions. Flat panel displays can also be made in large sizes, whereas 38 to 40 was about the largest size of a CRT television, flat panels are available in 60. Cathode rays were discovered by Johann Hittorf in 1869 in primitive Crookes tubes and he observed that some unknown rays were emitted from the cathode which could cast shadows on the glowing wall of the tube, indicating the rays were traveling in straight lines. In 1890, Arthur Schuster demonstrated cathode rays could be deflected by electric fields, the earliest version of the CRT was known as the Braun tube, invented by the German physicist Ferdinand Braun in 1897. It was a diode, a modification of the Crookes tube with a phosphor-coated screen. In 1907, Russian scientist Boris Rosing used a CRT in the end of an experimental video signal to form a picture. He managed to display simple geometric shapes onto the screen, which marked the first time that CRT technology was used for what is now known as television. The first cathode ray tube to use a hot cathode was developed by John B. Johnson and Harry Weiner Weinhart of Western Electric and it was named by inventor Vladimir K. Zworykin in 1929. RCA was granted a trademark for the term in 1932, it released the term to the public domain in 1950. The first commercially made electronic television sets with cathode ray tubes were manufactured by Telefunken in Germany in 1934, in oscilloscope CRTs, electrostatic deflection is used, rather than the magnetic deflection commonly used with television and other large CRTs
38.
HSL and HSV
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HSL and HSV are the two most common cylindrical-coordinate representations of points in an RGB color model. The two representations rearrange the geometry of RGB in an attempt to be intuitive and perceptually relevant than the cartesian representation. Developed in the 1970s for computer applications, HSL and HSV are used today in color pickers, in image editing software. HSL stands for hue, saturation, and lightness, and is often called HLS. HSV stands for hue, saturation, and value, and is often called HSB. A third model, common in computer applications, is HSI. However, while typically consistent, these definitions are not standardized, note that while hue in HSL and HSV refers to the same attribute, their definitions of saturation differ dramatically. As a result, each unique RGB device has unique HSL and HSV absolute color spaces to accompany it, other more computationally intensive models, such as CIELAB or CIECAM02, are said to better achieve these goals. In each geometry, the vertical axis comprises the neutral, achromatic, or gray colors, ranging from black at lightness 0 or value 0, the bottom, to white at lightness 1 or value 1. These saturated colors have lightness ½ in HSL, while in HSV they have value 1, mixing these pure colors with black—producing so-called shades—leaves saturation unchanged. In HSL, saturation is also unchanged by tinting with white, in HSV, tinting alone reduces saturation. Confusingly, such diagrams usually label this radial dimension saturation, blurring or erasing the distinction between saturation and chroma, as described below, computing chroma is a helpful step in the derivation of each model. Most televisions, computer displays, and projectors produce colors by combining red, green, furthermore, neither additive nor subtractive color models define color relationships the same way the human eye does. For example, imagine we have an RGB display whose color is controlled by three sliders ranging from 0–255, one controlling the intensity of each of the red, green, consequently, these models and similar ones have become ubiquitous throughout image editing and graphics software since then. Some of their uses are described below, nonetheless, it is worth reviewing those definitions before leaping into the derivation of our models. Hue The attribute of a visual sensation according to which an area appears to be similar to one of the colors, red, yellow, green. Radiance The radiant power of passing through a particular surface per unit solid angle per unit projected area. Luminance The radiance weighted by the effect of each wavelength on a human observer
39.
Hue
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Orange and violet are the other hues, for a total of six, as in the rainbow, red, orange, yellow, green, blue, violet. The other color appearance parameters are colorfulness, chroma, saturation, lightness, usually, colors with the same hue are distinguished with adjectives referring to their lightness and/or colorfulness, such as with light blue, pastel blue, vivid blue. Exceptions include brown, which is a dark orange, in painting color theory, a hue refers to a pure color—one without tint or shade. A hue is an element of the color wheel, hues are first processed in the brain in areas in the extended V4 called globs. Hue is the component of the polar representation, while chroma is the radial component. Specifically, in CIELAB h a b = a t a n 2, while, analogously, in CIELUV h u v = a t a n 2 = a t a n 2, where, atan2 is a two-argument inverse tangent. Preucil describes a color hexagon, similar to a trilinear plot described by Evans, Hanson, and Brewer, to place red at 0°, green at 120°, and 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, which he termed a color circle. Using R, G, and B, one may compute hue angle using the scheme, determine which of the six possible orderings of R, G. Note that in case the formula contains the fraction M − L H − L, where H is the highest of R, G, and B, L is the lowest. This is referred to as the Preucil hue error and was used in the computation of mask strength in photomechanical color reproduction, the formulae used are those in the table above. The hues exhibited by caramel colorings and beers are fairly limited in range, the Linner hue index is used to quantify the hue of such products. Replacements are often used for chromium, cadmium and alizarin, dominant wavelength is a physical analog to the perceptual attribute hue. On a chromaticity diagram, a line is drawn from a point through the coordinates of the color in question. There are two ways in which hue difference is quantified. The first is the difference between the two hue angles. The symbol for expression of hue difference is Δ h a b in CIELAB. The other is computed as the total color difference after Lightness and Chroma differences have been accounted for, its symbol is Δ H a b ∗ in CIELAB
40.
Colorfulness
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Colorfulness or saturation in colorimetry and color theory refers to the perceived intensity of a specific color. Colorfulness is the visual sensation according to which the color of an area appears to be more or less chromatic. Chroma is the relative to the brightness of a similarly illuminated area that appears to be white or highly transmitting. Therefore, chroma should not be confused with colorfulness, saturation is the colorfulness of a color relative to its own brightness. A highly colorful stimulus is vivid and intense, while a less colorful stimulus appears more muted, with no colorfulness at all, a color is a “neutral” gray. Any color can be described using three color appearance parameters — colorfulness, lightness, and hue, saturation is one of three coordinates in the HSL and HSV color spaces. The saturation of a color is determined by a combination of light intensity, the purest color is achieved by using just one wavelength at a high intensity, such as in laser light. If the intensity drops, then as a result the saturation drops, to desaturate a color of given intensity in a subtractive system, one can add white, black, gray, or the hues complement. CIELUV The chroma normalized by the lightness, s u v = C u v ∗ L ∗ =132 +2 where is the chromaticity of the white point, and chroma is defined below. Nevertheless, this provides a reasonable predictor of saturation. S a b = C a b ∗ C a b ∗2 + L ∗2100 % where Sab is the saturation, L* the lightness and C*ab is the chroma of the color. CIECAM02 The square root of the colorfulness divided by the brightness, M is proportional to the chroma C, thus the CIECAM02 definition bears some similarity to the CIELUV definition. An important difference is that the CIECAM02 model accounts for the conditions through the parameter FL. Different color spaces, such as CIELAB or CIELUV may be used, the naïve definition of saturation does not specify its response function. However, both color spaces are nonlinear in terms of perceived color differences. It is also possible—and sometimes desirable—to define a quantity that is linearized in term of the psychovisual perception. The transformation of to is given by, C a b ∗ = a ∗2 + b ∗2 h a b = arctan b ∗ a ∗ and analogously for CIE L*C*h. The chroma in the CIE L*C*h and CIE L*C*h coordinates has the advantage of being more psychovisually linear, and therefore, chroma in CIE1976 L*a*b* and L*u*v* color spaces is very much different from the traditional sense of saturation
41.
Brightness
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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 and it is not necessarily 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 refers to an absolute term and 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, ultimately from a PIE root with a closely related meaning, *bhereg- white, bright. Brightness was formerly used as a synonym for the term luminance. 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, see, for example, Whites illusion. With regard to stars, brightness is quantified as apparent magnitude, brightness is, at least in some respects, the antonym of darkness. The United States Federal Trade Commission has assigned a meaning to brightness when applied to lamps. When appearing on light bulb packages, brightness means Luminous flux, Luminous flux is the total amount of light coming from a source, such as a lighting device. Luminance, the meaning of brightness, is the amount of light per solid angle coming from an area. The table below shows the ways of indicating the amount of light. The term brightness is used in discussions of sound timbres. Luma Luminance Luminosity Media related to brightness at Wikimedia Commons Poyntons Color FAQ
42.
Cylindrical coordinates
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The latter distance is given as a positive or negative number depending on which side of the reference plane faces the point. The origin of the system is the point where all three coordinates can be given as zero and this is the intersection between the reference plane and the axis. The third coordinate may be called the height or altitude, longitudinal position and they are sometimes called cylindrical polar coordinates and polar cylindrical coordinates, and are sometimes used to specify the position of stars in a galaxy. The three coordinates of a point P are defined as, The radial distance ρ is the Euclidean distance from the z-axis to the point P. The azimuth φ is the angle between the direction on the chosen plane and the line from the origin to the projection of P on the plane. The height z is the distance from the chosen plane to the point P. As in polar coordinates, the point with cylindrical coordinates has infinitely many equivalent coordinates, namely and. Moreover, if the radius ρ is zero, the azimuth is arbitrary, in situations where someone wants a unique set of coordinates for each point, one may restrict the radius to be non-negative and the azimuth φ to lie in a specific interval spanning 360°, such as. The notation for cylindrical coordinates is not uniform, the ISO standard 31-11 recommends, where ρ is the radial coordinate, φ the azimuth, and z the height. However, the radius is often denoted r or s, the azimuth by θ or t. In concrete situations, and in many illustrations, a positive angular coordinate is measured counterclockwise as seen from any point with positive height. The cylindrical coordinate system is one of many coordinate systems. The following formulae may be used to convert between them, the arcsin function is the inverse of the sine function, and is assumed to return an angle in the range =. These formulas yield an azimuth φ in the range, for other formulas, see the polar coordinate article. Many modern programming languages provide a function that will compute the correct azimuth φ, in the range, given x and y, for example, this function is called by atan2 in the C programming language, and atan in Common Lisp. In many problems involving cylindrical polar coordinates, it is useful to know the line and volume elements, the line element is d r = d ρ ρ ^ + ρ d φ φ ^ + d z z ^. The volume element is d V = ρ d ρ d φ d z, the surface element in a surface of constant radius ρ is d S ρ = ρ d φ d z. The surface element in a surface of constant azimuth φ is d S φ = d ρ d z, the surface element in a surface of constant height z is d S z = ρ d ρ d φ
Color vision.
