1.
SRGB color space
–
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
SRGB color space
2.
Red
–
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
Red
–
Pure, or solid red, the color of most ripe
strawberries.
Red
–
Red
Red
–
Scarlet is one quarter of the way between the colors red and orange. It is the color worn by a
cardinal of the
Roman Catholic Church..
Red
–
The
cardinal takes its name from the color worn by Roman Catholic
cardinals.
3.
Green
–
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
Green
–
The word green has the same Germanic root as the words for grass and grow.
Green
–
Green
Green
–
Emerald green. The
Gachala Emerald from the
National Museum of Natural History, Washington.
Green
–
Jade. A jade dragon from the
Han Dynasty, China. Jade can be many different shades of green.
4.
Blue
–
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
Blue
–
Sky blue or pale
azure, mid-way on the RBG colour wheel between blue and cyan.
Blue
–
Blue
Blue
–
Extract of natural
indigo, the most popular blue dye before the invention of synthetic dyes. It was the colour of the first
blue jeans.
Blue
–
A block of
lapis lazuli, originally used to make ultramarine.
5.
CMYK color model
–
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
CMYK color model
–
A color photograph of the
Teton Range.
CMYK color model
–
Color printing typically uses ink of four colors: cyan, magenta, yellow, and key (black).
CMYK color model
–
The image above, separated for printing with process cyan, magenta, and yellow inks.
CMYK color model
–
The same image, this time separated with maximum black, to minimize ink use.
6.
Cyan
–
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
Cyan
–
In the
RGB color model, used to make colors on computer and TV displays, cyan is created by the combination of green and blue light.
Cyan
–
Cyan
Cyan
–
Color printers today use magenta, cyan, and yellow ink to produce the full range of colors.
Cyan
–
Cyan is the color of shallow water over a sandy beach. The water absorbs the color red from the sunlight, leaving a greenish-blue color.
7.
Yellow
–
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
Yellow
–
Yellow is the color of
gold,
butter, and ripe
lemons.
Yellow
–
Yellow
Yellow
–
Image of a horse colored with
yellow ochre. from
Lascaux cave.
Yellow
–
Paintings in the Tomb of Nakht in
ancient Egypt (15th century BC).
8.
Black
–
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
Black
–
Outer space seen from Mars (Image taken by
NASA 's
MER Spirit rover)
Black
–
Neolithic paintings of bulls in the
Lascaux Cave, more than 17,000 years old
Black
–
Statue of Anubis, guardian of the underworld, from the tomb of
Tutankhamun.
Black
–
Greek
Black-figure pottery.
Ajax and
Achilles playing a game, about 540-530 BC. (Vatican Museums).
9.
HSV color space
–
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
HSV color space
–
Fig. 13a. Color photograph
HSV color space
HSV color space
–
b. CIELAB L *
HSV color space
–
c. Rec. 601 luma Y ′
10.
Saturation (color theory)
–
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
Saturation (color theory)
–
Original image, with relatively muted colors
Saturation (color theory)
–
L*C*h (
CIELAB) chroma increased 50%
Saturation (color theory)
–
HSL saturation increased 50%; notice that changing HSL saturation also affects the perceived lightness of a color
Saturation (color theory)
–
CIELAB lightness preserved, with a * and b * stripped, to make a
grayscale image
11.
Brightness
–
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
Brightness
–
Decreasing brightness with depth (underwater photo as example)
12.
Color
–
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
Color
–
Colored pencils
13.
Purple
–
Purple is a color intermediate between blue and red. It is similar to violet, but unlike violet, which is a color with its own wavelength on the visible spectrum of light, purple is a composite color made by combining red. According to surveys In Europe and the U. S. purple is the color most often associated with royalty, magic, mystery, when combined with pink, it is associated with eroticism, femininity and seduction. Purple was the color worn by Roman magistrates, it became the color worn by the rulers of the Byzantine Empire and the Holy Roman Empire. Similarly in Japan, the color is associated with the Emperor. The first recorded use of the purple in the English language was in the year 975 AD. In heraldry, the word purpure is used for purple, in the traditional color wheel used by painters, violet and purple are both placed between red and blue. Purple occupies the space closer to red, between crimson and violet, violet is closer to blue, and is usually less saturated than purple. While the two look similar, from the point of view of optics there are important differences. There is no such thing as the wavelength of purple light, monochromatic violet light cannot be produced by the red-green-blue color system, the method used to create colors on a television screen or computer display. This means that when light strikes the eye, the S-cone should be stimulated strongly. The resulting color has the same hue as pure violet, however, one curious psychophysical difference between purple and violet is their appearance with an increase in luminance. Violet, as it brightens, looks more and more blue, the same effect does not happen with purple. This is the result of what is known as the Bezold–Brücke shift, while the scientific definitions of violet and purple are clear, the cultural definitions are more varied. The color known in antiquity as Tyrian purple ranged from crimson to a deep bluish-purple, in France, purple is defined as a dark red, inclined toward violet. The color called purple by the French, pourpre, contains red and half the amount of blue of the color called purple in the United States. In German, this color is sometimes called Purpurrot to avoid confusion, Purple first appeared in prehistoric art during the Neolithic era. These works have been dated to between 16,000 and 25,000 BC, as early as the 15th century BC the citizens of Sidon and Tyre, two cities on the coast of Ancient Phoenicia, were producing purple dye from a sea snail called the spiny dye-murex
Purple
–
Purple is the color of royalty. A ticket for the coronation of
Elizabeth II (1953)
Purple
–
Purple
Purple
–
In Catholicism purple is a
liturgical color representing piety
Purple
–
Purple has become a popular color for
neckties; it is less aggressive than red, but more active than blue.
14.
Pink
–
Pink is a pale red color which takes its name from the flower of the same name. According to surveys in Europe and the United States, pink is the color most often associated with charm, politeness, sensitivity, tenderness, sweetness, childhood, femininity, when combined with white, it is associated with innocence. When combined with violet or black, it is associated with eroticism, Pink was first used as a color name in the late 17th century. The color pink is named after the flowers called pinks, flowering plants in the genus Dianthus, the name derives from the frilled edge of the flowers—the verb to pink dates from the 14th century and means to decorate with a perforated or punched pattern. The color pink has been described in literature since ancient times, in the Odyssey, written in approximately 800 BCE, Homer wrote Then, when the child of morning, rosy-fingered dawn appeared. Roman poets also described the color, roseus is the Latin word meaning rosy or pink. Lucretius used the word to describe the dawn in his epic poem On the Nature of Things, Pink was not a common color in the fashion of the Middle Ages, nobles usually preferred brighter reds, such as crimson. However, it did appear in fashion, and in religious art. In the 13th and 14th century, in works by Cimabue and Duccio, the Christ child was sometimes portrayed dressed in pink, in the high Renaissance painting the Madonna of the Pinks by Raphael, the Christ child is presenting a pink flower to the Virgin Mary. The pink was a symbol of marriage, showing a spiritual marriage between the mother and child, during the Renaissance, pink was mainly used for the flesh color of faces and hands. John’s white, as it is called in Florence, and this white is made from thoroughly white, and when these two pigments have been thoroughly mulled together, make little loaves of them like half walnuts and leave them to dry. When you need some, take much of it seems appropriate. And this pigment does you great credit if you use it for painting faces, hands, the golden age of the color pink was the Rococo Period in the 18th century, when pastel colors became very fashionable in all the courts of Europe. Pink was particularly championed by Madame de Pompadour, the mistress of King Louis XV of France. Who wore combinations of blue and pink, and had a particular tint of pink made for her by the Sevres porcelain factory, created by adding nuances of blue, black. In this painting, it symbolized childhood, innocence and tenderness, sarah Moulton was just eleven years old when the picture was painted, and died the following year. In 19th century England, pink ribbons or decorations were worn by young boys, boys were simply considered small men. In fact the clothing for children in the 19th century was almost always white, since, before the invention of chemical dyes, queen Victoria was painted in 1850 with her seventh child and third son, Prince Arthur, who wore white and pink
Pink
–
The color pink takes its name from the flowers called
pinks, members of the genus
Dianthus.
Pink
–
Pink
Pink
–
In most European languages, pink is called rose or rosa, after the
rose flower.
Pink
–
Cherry blossoms in Senai, Miyagi, Japan. The Japanese language has different words for the pink of cherry blossoms (sakura-iro), and peach blossoms (momo-iro). Recently the word pinku has also become popular.
15.
Mauve
–
Mauve is a pale purple color named after the mallow flower. The first use of the word mauve as a color was in 1796–98 according to the Oxford English Dictionary, another name for the color is mallow, with the first recorded use of mallow as a color name in English in 1611. Mauve contains more grey and more blue than a pale tint of magenta, many pale wildflowers called blue are actually mauve. Mauve is also described as pale violet. The synthetic dye mauve was first so named in 1859, chemist William Henry Perkin, then eighteen, was attempting to create a cure for Malaria in 1856. Earlier references to a dye in 1856–58 referred to a color produced using the semi-synthetic dye murexide or a mixture of natural dyes. Perkin was so successful in marketing his discovery to the dye industry that his biography by Simon Garfield is simply entitled Mauve, however, as it faded easily, the success of mauve dye was short-lived and it was replaced by other synthetic dyes by 1873. As the memory of the original dye soon receded, the understanding of mauve is as a lighter. The 1890s are sometimes referred to in retrospect as the Mauve Decade, because of the popularity of the subtle color among progressive artistic types. At right is displayed the tone of mauve that is called mauve in Crayola colored pencils. At right is displayed the tone of mauve that is called mauve in Pourpre. com. At right is displayed the color opera mauve, the first recorded use of opera mauve as a color name in English was in 1927. The color displayed at right is mauve taupe, the first recorded use of mauve taupe as a color name in English was in 1925. See the article on taupe to see shades of taupe. At right is displayed the color old mauve, the first recorded use of old mauve as a color name in English was in 1925. The source of color is the ISCC-NBS Dictionary of Color Names —a color dictionary used by stamp collectors to identify the colors of stamps. The mauve stinger is a jellyfish that is distributed in all warm. Mauve is a commonly used color in stage lighting to represent sunsets, list of colors Malvaria, from the term mauve factor in Orthomolecular psychiatry
Mauve
–
Mallow wildflower
16.
Crimson
–
Crimson is a strong, red color, inclining to purple. Crimson is produced using the bodies of the kermes insect, which were gathered commercially in Mediterranean countries, where they live on the kermes oak. Kermes dyes have been found in burial wrappings in Anglo-Scandinavian York, carmine is the name given to the dye made from the dried bodies of the female cochineal, although the name crimson is sometimes applied to these dyes too. Cochineal appears to have brought to Europe during the conquest of Mexico by the Spaniard Hernán Cortés. It was first described by Mathioli in 1549, the pigment is also called cochineal after the insect from which it is made. Alizarin is a pigment that was first synthesized in 1868 by the German chemists Carl Gräbe and Carl Liebermann, alizarin crimson is a dye bonded onto alum which is then used as a pigment and mixed with ochre, sienna and umber. The word crimson has been recorded in English since 1400, and its earlier forms include cremesin, crymysyn, German Karmesin, Italian Cremisi, French cramoisi, Portuguese carmesim, etc. The ultimate source may be Sanskrit कृमिज kṛmi-jā meaning worm-made, a shortened form of carmesinus also gave the Latin carminus, from which comes carmine. Other cognates include the Old Church Slavic čruminu, archaic Russian чермный, carmine dyes, which give crimson and related red and purple colors, are based on an aluminium and calcium salt of carminic acid. Carmine lake is an aluminium or aluminium-tin lake of cochineal extract, purple lake is prepared like carmine lake with the addition of lime to produce the deep purple tone. Carmine dyes tend to fade quickly, carmine dyes were once widely prized in both the Americas and in Europe. They were used in paints by Michelangelo and for the fabrics of the Hussars, the Turks, the British Redcoats. Nowadays carmine dyes are used for coloring foodstuffs, medicines and cosmetics, as a food additive in the European Union, carmine dyes are designated E120, and are also called cochineal and Natural Red 4. Carmine dyes are used in some oil paints and watercolors used by artists. The color pink is displayed on the right, the color pink has a hue code of 350, placing it directly within the range of crimson colors. Thus, the pink is actually a pale tint of crimson. The color Baker-Miller Pink is displayed on the right, Baker-Miller Pink was formulated in 1979. With a hue code of 344, Baker-Miller Pink is within the range of crimson colors, the color fandango pink is displayed on the right
Crimson
–
The ornamental grape crimson glory vine autumn colors
17.
Color wheel
–
A color wheel or colour circle is an abstract illustrative organization of color hues around a circle, which shows the relationships between primary colors, secondary colors, tertiary colors etc. Some sources use the color wheel and color circle interchangeably, however. For instance, some reserve the term color wheel for mechanical rotating devices, others classify various color wheels as color disc, color chart, and color scale varieties. As an illustrative model, artists typically use red, yellow, printers and others who use modern subtractive color methods and terminology use magenta, yellow, and cyan as subtractive primaries. Intermediate and interior points of color wheels and circles represent color mixtures, modern color circles include the purples, however, between red and violet. Color scientists and psychologists use the additive primaries, red, green and blue. The typical artists paint or pigment color wheel includes the blue, red, the corresponding secondary colors are green, orange, and violet or purple. The tertiary colors are green-yellow, yellow–orange, orange-red, red–violet, violet-blue, a color wheel based on RGB or RGV additive primaries has cyan, magenta, and yellow secondaries. Alternatively, the arrangement of colors around a circle can be described as based on cyan, magenta, and yellow subtractive primaries, with red, green. Other color wheels, however, are based on the four opponent colors, goethes Theory of Colours provided the first systematic study of the physiological effects of color. Are those that reciprocally evoke each other in the eye, a color circle based on spectral wavelengths appears with red at one end of the spectrum and violet at the other. A wedge-shaped gap represents colors that have no unique spectral frequency and these extra-spectral colors, the purples, form from additive mixture of colors from the ends of the spectrum. In normal human vision, wavelengths of between about 400 nm and 700 nm are represented by this circle, with the longer wavelengths equating to the red end of the spectrum. Complement colors are located directly opposite each other on this wheel and these complement colors are not identical to colors in pigment mixing, but when lights are additively mixed in the correct proportions appear as a neutral grey or white. For example, the reason that the Wimbledon tennis tournament uses purple on the Wimbledon official logo is that purple is located almost opposite of green on the color wheel, purple against green provides good contrast. The color circle is used for, among other purposes, illustrating additive color mixture and this type of color matching is known as metameric matching. Thus a combination of green and red light might produce a close to yellow in apparent hue. The combination of any two colors in this way are always less saturated than the two pure spectral colors individually, objects may be viewed under a variety of different lighting conditions
Color wheel
–
Boutet's 7-color and 12-color color circles from 1708
Color wheel
–
Wilhelm von Bezold's 1874 Farbentafel
Color wheel
Color wheel
18.
RGB color model
–
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
RGB color model
–
A representation of additive color mixing. Projection of
primary color lights on a screen shows secondary colors where two overlap; the combination of all three of red, green, and blue in equal intensities makes white.
RGB color model
–
The first permanent color photograph, taken by
J.C. Maxwell in 1861 using three filters, specifically red, green, and violet-blue.
RGB color model
–
A photograph of
Mohammed Alim Khan (1880–1944),
Emir of Bukhara, taken in 1911 by
Sergei Mikhailovich Prokudin-Gorskii using three exposures with red, green, and blue filters.
RGB color model
–
RGB
phosphor dots in a
CRT monitor
19.
Subtractive color
–
The color that a surface displays depends on which parts of the visible spectrum are not absorbed and therefore remain visible. Subtractive color systems start with light, presumably white light, colored inks, paints, or filters between the watchers and the light source or reflective surface subtract wavelengths from the light, giving it color. If the incident light is other than white, our visual mechanisms are able to compensate well, conversely, additive color systems start with darkness. Light sources of various wavelengths are added in proportions to produce a range of colors. Usually, three colors are combined to stimulate humans’ trichromatic color vision, sensed by the three types of cone cells in the eye, giving an apparently full range. RYB is the standard set of subtractive primary colors used for mixing pigments. It is used in art and art education, particularly in painting and it predated modern scientific color theory. Red, yellow, and blue are the colors of the standard color wheel. The secondary colors, violet, orange, and green make up another triad, formed by mixing equal amounts of red and blue, red and yellow, in color printing, the usual primary colors are cyan, magenta and yellow. Cyan is the complement of red, meaning that the cyan serves as a filter that absorbs red, the amount of cyan applied to a white sheet of paper controls how much of the red in white light will be reflected back from the paper. Ideally, the cyan is completely transparent to green and blue light and has no effect on those parts of the spectrum, magenta is the complement of green, and yellow the complement of blue. Combinations of different amounts of the three can produce a range of colors with good saturation. In inkjet color printing and typical mass production photomechanical printing processes, additive color Color mixing Color motion picture film Color space Color theory Primary color Berns, Roy S. Billmeyer and Saltzmans Principles of Color Technology, 3rd edition. Stroebel, Leslie, John Compton, Ira Current, and Richard Zakia, basic Photographic Materials and Processes, 2nd edition. CS1 maint, Multiple names, authors list Wyszecki, Günther & W. S. Stiles, colour Science, Concept and Methods, Quantitative Data and Formulae. Stanford University CS178 interactive Flash demo comparing additive and subtractive color mixing
Subtractive color
–
An 1877 color photo by
Louis Ducos du Hauron, a French pioneer of
color photography. The overlapping subtractive yellow, cyan and red (magenta) image elements can be seen clearly along the edges of the image.
Subtractive color
–
Subtractive color mixing
20.
Complementary color
–
Complementary colors are pairs of colors which, when combined, cancel each other out. This means that combined, they produce a grey-scale color like white or black. When placed next to other, they create the strongest contrast for those particular two colors. Due to this striking color clash, the term opposite colors is considered more appropriate than complementary colors. Opponent process theory suggests that the most contrasting color pairs are red–green, in the traditional representation, a complementary color pair is made up of a primary color and a secondary color. For example, yellow is a color, and painters can make purple by mixing of red and blue, so when yellow and purple paint are mixed. Since paints work by absorbing light, having all three primaries together results in a black or gray color, in more recent painting manuals, the more precise subtractive primary colors are magenta, cyan and yellow. Complementary colors can create some striking optical effects, the shadow of an object appears to contain some of the complementary color of the object. For example, the shadow of a red apple will appear to contain a little blue-green and this effect is often copied by painters who want to create more luminous and realistic shadows. Also, if you stare at a square of color for a period of time. Placed side by side as tiny dots, in color mixing. In the RGB model, the colors are red, green. The complementary primary–secondary combinations are red–cyan, green–magenta, and blue–yellow, if the light is not fully intense, the resulting light will be gray. In some other models, such as the HSV color space. Complementary colors lie opposite each other on any horizontal cross-section, for example, in the CIE1931 color space a color of a dominant wavelength can be mixed with an amount of the complementary wavelength to produce a neutral color. Color printing, like painting, also uses subtractive colors, but the colors are different from those used in painting. As a result, the logic applies as to colors produced by light. Color printing uses the CMYK color model, making colors by overprinting cyan, magenta, yellow, in printing the most common complementary colors are magenta–green, yellow–blue, and cyan–red
Complementary color
–
A Boutet color circle from 1708 showed the traditional complementary colors; red and green, yellow and violet, and blue and orange.
Complementary color
–
A traditional color star developed in 1867 by
Charles Blanc. The traditional complementary colors used by 19th-century artists such as Van Gogh, Monet and Renoir are directly opposite each other.
Complementary color
–
The color wheel designed by
Johann Wolfgang von Goethe (1810) was based on the idea that the primary colors yellow and blue, representing light and darkness, were in opposition to each other.
Complementary color
–
Impression, Sunrise by
Claude Monet (1872) featured a tiny but vivid orange sun against a blue background. The painting gave its name to the Impressionist movement.
21.
Inkjet printer
–
Inkjet printing is a type of computer printing that recreates a digital image by propelling droplets of ink onto paper, plastic, or other substrates. Inkjet printers are the most commonly used type of printer, the concept of inkjet printing originated in the 20th century, and the technology was first extensively developed in the early 1950s. Starting in the late 1970s inkjet printers that could reproduce digital images generated by computers were developed, mainly by Epson, Hewlett-Packard, in the worldwide consumer market, four manufacturers account for the majority of inkjet printer sales, Canon, HP, Epson, and Brother. The emerging ink jet material deposition market also uses inkjet technologies, typically printheads using piezoelectric crystals, the technology has been extended and the ″ink″ can now also comprise living cells, for creating biosensors and for tissue engineering. There are two main technologies in use in contemporary inkjet printers, continuous and Drop-on-demand, the continuous inkjet method is used commercially for marking and coding of products and packages. In 1867 Lord Kelvin patented the syphon recorder, which recorded telegraph signals as a trace on paper using an ink jet nozzle deflected by a magnetic coil. The first commercial devices were introduced in 1951 by Siemens, the ink droplets are subjected to an electrostatic field created by a charging electrode as they form, the field varies according to the degree of drop deflection desired. This results in a controlled, variable electrostatic charge on each droplet, charged droplets are separated by one or more uncharged guard droplets to minimize electrostatic repulsion between neighbouring droplets. The more highly charged droplets are deflected to a greater degree, only a small fraction of the droplets is used to print, the majority being recycled. CIJ is one of the oldest ink jet technologies in use and is fairly mature, viscosity is monitored and a solvent is added to counteract solvent loss. Drop-on-demand is divided into thermal DOD and piezoelectric DOD, most consumer inkjet printers, including those from Canon, Hewlett-Packard, and Lexmark, use the thermal inkjet process. Vaughts work started in late 1978 with a project to develop fast, low-cost printing, the team at HP found that thin-film resistors could produce enough heat to fire an ink droplet. Two years later the HP and Canon teams found out about each others work, in the thermal inkjet process, the print cartridges consist of a series of tiny chambers, each containing a heater, all of which are constructed by photolithography. The inks involved are usually water-based and use either pigments or dyes as the colorant, the inks must have a volatile component to form the vapor bubble, otherwise droplet ejection cannot occur. As no special materials are required, the print head is generally cheaper to produce than in other inkjet technologies, most commercial and industrial inkjet printers and some consumer printers use a piezoelectric material in an ink-filled chamber behind each nozzle instead of a heating element. When a voltage is applied, the material changes shape, generating a pressure pulse in the fluid. A DOD process uses software that directs the heads to apply between zero and eight droplets of ink per dot, only where needed, piezo inkjet technology is often used on production lines to mark products. For instance, the date is often applied to products with this technique, in this application the head is stationary
Inkjet printer
–
An
Epson inkjet printer
Inkjet printer
–
A Canon inkjet with
CMYK cartridges
Inkjet printer
–
Piezoelectric printing nozzle of an EPSON C20 printer.
22.
Printing
–
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
Printing
–
The intricate frontispiece of the
Diamond Sutra from
Tang Dynasty China, 868 A.D. (
British Library)
Printing
–
The earliest known
woodcut, 1423,
Buxheim, with hand-colouring
Printing
–
Copperplate of 1215–1216 5000
cash paper money with ten bronze movable types
23.
Aniline
–
Aniline is an organic compound with the formula C6H5NH2. Consisting of a group attached to an amino group, aniline is the prototypical aromatic amine. Its main use is in the manufacture of precursors to polyurethane, like most volatile amines, it possesses the odour of rotten fish. It ignites readily, burning with a smoky flame characteristic of aromatic compounds, the amine is nearly planar owing to conjugation of the lone pair with the aryl substituent. The C-N distance is correspondingly shorter, in aniline, the C-N and C-C distances are close to 1.39 Å, indicating the π-bonding between N and C. Industrial aniline production involves two steps, first, benzene is nitrated with a concentrated mixture of nitric acid and sulfuric acid at 50 to 60 °C to yield nitrobenzene. The nitrobenzene is then hydrogenated in the presence of metal catalysts, the reduction of nitrobenzene to aniline was first performed by Nikolay Zinin in 1842 using inorganic sulfide as a reductant. Aniline can alternatively be prepared from ammonia and phenol derived from the cumene process, many analogues of aniline are known where the phenyl group is further substituted. These include toluidines, xylidines, chloroanilines, aminobenzoic acids, nitroanilines and they often are prepared by nitration of the substituted aromatic compounds followed by reduction. For example, this approach is used to convert toluene into toluidines, the chemistry of aniline is rich because the compound has been cheaply available for many years. Below are some classes of its reactions, the oxidation of aniline has been heavily investigated, and can result in reactions localized at nitrogen or more commonly results in the formation of new C-N bonds. In alkaline solution, azobenzene results, whereas arsenic acid produces the violet-coloring matter violaniline, chromic acid converts it into quinone, whereas chlorates, in the presence of certain metallic salts, give aniline black. Hydrochloric acid and potassium chlorate give chloranil, potassium permanganate in neutral solution oxidizes it to nitrobenzene, in alkaline solution to azobenzene, ammonia and oxalic acid, in acid solution to aniline black. Hypochlorous acid gives 4-aminophenol and para-amino diphenylamine, oxidation with persulfate affords a variety of polyanilines compounds. These polymers exhibit rich redox and acid-base properties, like phenols, aniline derivatives are highly susceptible to electrophilic substitution reactions. Its high reactivity reflects that it is an enamine, which enhances the ability of the ring. For example, reaction of aniline with sulfuric acid at 180 °C produces sulfanilic acid, if bromine water is added to aniline, the bromine water is decolourised and a white precipitate of 2,4, 6-tribromophenylamine is formed. The largest scale industrial reaction of aniline involves its alkylation with formaldehyde, an idealized equation is shown,2 C6H5NH2 + CH2O → CH22 + H2O The resulting diamine is the precursor to 4, 4-MDI and related diisocyanates
Aniline
–
Cake of
indigo dye, which is prepared from aniline.
Aniline
24.
Fuchsine
–
Fuchsine or rosaniline hydrochloride is a magenta dye with chemical formula C20H19N3·HCl. There are other similar chemical formulations of products sold as fuchsine and it becomes magenta when dissolved in water, as a solid, it forms dark green crystals. As well as dying textiles, fuchsine is used to stain bacteria, in the literature of biological stains the name of this dye is frequently misspelled, with omission of the terminal -e, which indicates an amine. American and English dictionaries give the spelling, which is also used in the literature of industrial dyeing. It is well established that production of fuchsine results in development of bladder cancers by production workers, production of magenta is listed as a circumstance known to result in cancer. Fuchsine was first prepared by August Wilhelm von Hofmann from aniline, françois-Emmanuel Verguin discovered the substance independently of Hofmann the same year and patented it. An 1861 article in Répertoire de Pharmacie said that the name was chosen for both reasons, Acid fuchsine is a mixture of homologues of basic fuchsine, modified by addition of sulfonic groups. While this yields twelve possible isomers, all of them are satisfactory despite slight differences in their properties, basic fuchsine is a mixture of rosaniline, pararosaniline, new fuchsine and Magenta II. Formulations usable for making of Schiff reagent must have content of pararosanilin. The actual composition of basic fuchsine tends to vary by vendor and batch. In solution with phenol as an accentuator it is called carbol fuchsin and is used for the Ziehl–Neelsen and other similar acid-fast staining of the mycobacteria which cause tuberculosis, leprosy etc. Basic fuchsine is used in biology to stain the nucleus. The crystals pictured at the right are of basic fuchsine, also known as basic violet 14, basic red 9 and their structure differs from the structure shown above by the absence of the methyl group on the upper ring, otherwise they are quite similar. They are soft, with a hardness of less than 1 and they possess a strong metallic lustre and a green yellow color. They leave dark greenish streaks on paper and when these are moistened with a solvent, the strong magenta colour appears. The two magenta stains on the paper were made by placing one drop of ethanol-water azeotrope, centre, the crystals were then replaced and the photograph taken. Fuchsine is a salt and has three amine groups, two primary amines and a secondary amine. If one of these is protonated to form ABCNH+, the charge is delocalized across the whole symmetrical molecule due to pi cloud electron movement
Fuchsine
–
Solid Basic Fuchsine
Fuchsine
–
Fuchsine
Fuchsine
–
Basic Fuchsine in aqueous solution
Fuchsine
–
Picture of Basic Fuchsine Pieces, C.I. 42500.
25.
Battle of Magenta
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It took place near the town of Magenta in northern Italy on 4 June 1859. Napoleon IIIs army crossed the Ticino River and outflanked the Austrian right forcing the Austrian army under Gyulai to retreat, the confined nature of the country, a vast spread of orchards cut up by streams and irrigation canals, precluded elaborate manoeuvre. The Austrians turned every house into a miniature fortress, the brunt of the fighting was borne by 5,000 grenadiers of the French Imperial Guard, still mostly in First Empire style uniform. The battle of Magenta was not particularly large, but it was a victory for the French-Sardinian forces. Patrice Maurice de MacMahon was created Duke of Magenta for his role in this battle, the French-Piedmontese coalition comprised an overwhelming majority of French troops. Their victory can therefore be considered as substantially a French victory, a dye producing the colour magenta was discovered in 1859, and was named after this battle, as was the Boulevard de Magenta in Paris
Battle of Magenta
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The Battle of Magenta by
Gerolamo Induno.
Musée de l'Armée, Paris
Battle of Magenta
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Sword of honour
26.
Magenta, Lombardy
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Magenta is a town and comune in the province of Milan in Lombardy, northern Italy. It is notable as the site of the Battle of Magenta, the colour magenta is named after the battle, most likely referring to the uniforms used by Zouave French troops. Magenta is the birthplace of St. Gianna Beretta Molla, Magenta was probably a settlement of the Insubres, a Celtic tribe, who founded it around the 5th century BC. The area was conquered by the Romans in 222 BC, the name is traditionally connected to castrum Maxentiae, meaning castle of Maxentius. After the fall of the Western Roman Empire, it was ruled by the Lombards, objects, jewelry and weapons were found here. In the Middle Ages, it was destroyed twice, in 1162 by Frederick Barbarossa, in 1310, according to a legend, the emperor Henry VII was stopped here by a snowstorm during his march to Milan. In 1398 Gian Galeazzo Visconti donated the town territories to the monks of the Certosa di Pavia, on June 4,1859, it was the site of an important battle of the Second War of Italian Independence. The Franco-Piedmontese victory in the fight gave them the chance to conquer Austrian Lombardy, Magenta received the honorary title of city with a presidential decree on May 25,1947. Church of San Martino, built to commemorate the dead of the 1859 battle, monastery of Santa Maria Assunta, probably dating from the 14th century. The church, of Romanesque origin but with Baroque interiors, houses two works by il Bergognone, casa Crivelli Boisio Beretta, an example of 15th-century noble house. Casa Giacobbe Monument to general Patrice de MacMahon, la Fagiana natural park, a former hunting resort of King Victor Emmanuel II. Magenta is twinned with, Magenta, Marne, France SantAnna di Stazzema, Italy
Magenta, Lombardy
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Saint Martin Church
Magenta, Lombardy
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Main square.
Magenta, Lombardy
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Magenta former Library.
27.
Fuchsia (color)
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Fuchsia is a vivid purplish red color, named after the color of the flower of the fuchsia plant, which took its name from the 16th century German botanist Leonhart Fuchs. The color fuchsia was first introduced as the color of a new aniline dye called fuchsine, patented in 1859 by the French chemist François-Emmanuel Verguin. The dye was renamed later in the same year, to celebrate a victory of the French army at the Battle of Magenta on June 4,1859. In color printing and design, there are variations between magenta and fuchsia. Fuchsia is usually a more color, whereas magenta is more reddish. Fuchsia flowers themselves contain a variety of purples. The first recorded use of fuchsia as a name in English was in 1892. The first synthetic dye the color of fuchsia, called fuchsine, was patented in 1859 by François-Emmanuel Verguin and it was later renamed magenta, and became highly popular under that name. The name fuchsia is used on the HTML web color list for this color and they are both composed the same way, by combining an equal amount of blue and red light at full brightness, as shown in the image on the left. Displayed at right is the pale tint of fuchsia. The first recorded use of fuchsia as a color name in English was in 2014. At right is displayed the color French fuchsia, which is the tone of fuchsia called fuchsia in a color list popular in France, fashion fuchsia is a color used in fashion when a slightly less saturated color than shocking pink is desired. It also goes by the name Hollywood cerise, Fuchsia rose is the color that was chosen as the 2001 Pantone color of the year by Pantone. The source of color is the Pantone Textile Paper eXtended color list. Although red-purple is a seldom used color name in English, in Spanish it is regarded one of the tones of purple. The color fuchsia purple is displayed at right, the source of this color is the Pantone Textile Paper eXtended color list, color #18-2436 TPX—Fuchsia Purple. Deep fuchsia is the color that is called fuchsia in the List of Crayola crayon colors, displayed at right is the color fandango. The first recorded use of fandango as a name in English was in 1925
Fuchsia (color)
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Flower of
Fuchsia plant
Fuchsia (color)
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A sample of fuchsine dye in an aqueous solution.
Fuchsia (color)
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Crystals of fuchsine dye and the color they produce.
Fuchsia (color)
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On computer screens, red and blue light combined at full intensity produce fuchsia or magenta. The two web colors are identical, and have the same hex code, FF00FF.
28.
Spectral color
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A spectral color is a color that is evoked by a single wavelength of light in the visible spectrum, or by a relatively narrow band of wavelengths, also known as monochromatic light. Every wavelength of light is perceived as a spectral color, in a continuous spectrum. The spectrum is divided into named colors, though any division is somewhat arbitrary. Traditional colors include, red, orange, yellow, green, blue, and violet. The division used by Isaac Newton, in his wheel, was, red, orange, yellow, green, blue, indigo and violet. In modern divisions of the spectrum, indigo is often omitted, if luminance is counted, then spectral colors form a surface, otherwise their locus is a curve in a two-dimensional chromaticity space. Theoretically, only RGB-implemented colors which might be really spectral are its primaries, red, green, some samples in the table below provide only rough approximations of spectral and near-spectral colors. Ranges of wavelengths and frequencies are only approximate, among some of the colors that are not spectral colors are, Grayscale colors, such as white, gray, and black. Any color obtained by mixing a gray-scale color and another color, violet-red colors, which in color theory include line of purples colors, and other variations of purple and red. Impossible colors, which can not be seen under normal viewing of light, such as over-saturated colors or colors that are seemingly brighter than white
Spectral color
29.
Visible spectrum
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The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called light or simply light. A typical human eye will respond to wavelengths from about 390 to 700 nm, in terms of frequency, this corresponds to a band in the vicinity of 430–770 THz. The spectrum does not, however, contain all the colors that the human eyes, unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths. Colors containing only one wavelength are called pure colors or spectral colors. Visible wavelengths pass through the window, the region of the electromagnetic spectrum that allows wavelengths to pass largely unattenuated through the Earths atmosphere. An example of this phenomenon is that clean air scatters blue light more than red wavelengths, the optical window is also referred to as the visible window because it overlaps the human visible response spectrum. The near infrared window lies just out of the vision, as well as the Medium Wavelength IR window. In the 13th century, Roger Bacon theorized that rainbows were produced by a process to the passage of light through glass or crystal. In the 17th century, Isaac Newton discovered that prisms could disassemble and reassemble white light and he was the first to use the word spectrum in this sense in print in 1671 in describing his experiments in optics. The result is red light is bent less sharply than violet as it passes through the prism. Newton divided the spectrum into seven named colors, red, orange, yellow, green, blue, indigo, the human eye is relatively insensitive to indigos frequencies, and some people who have otherwise-good vision cannot distinguish indigo from blue and violet. For this reason, some commentators, including Isaac Asimov, have suggested that indigo should not be regarded as a color in its own right. However, the evidence indicates that what Newton meant by indigo, comparing Newtons observation of prismatic colors to a color image of the visible light spectrum shows that indigo corresponds to what is today called blue, whereas blue corresponds to cyan. In the 18th century, Goethe wrote about optical spectra in his Theory of Colours, Goethe used the word spectrum to designate a ghostly optical afterimage, as did Schopenhauer in On Vision and Colors. Goethe argued that the spectrum was a compound phenomenon. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum but rather reddish-yellow, the spectrum appears only when these edges are close enough to overlap. Young was the first to measure the wavelengths of different colors of light, the connection between the visible spectrum and color vision was explored by Thomas Young and Hermann von Helmholtz in the early 19th century
Visible spectrum
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White
light is
dispersed by a
prism into the colors of the visible spectrum.
Visible spectrum
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Newton's observation of prismatic colors (
David Brewster 1855)
30.
Line of purples
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In color theory, the line of purples or the purple boundary is the locus on the edge of the chromaticity diagram between extreme spectral red and violet. Except for the endpoints, colors on the line of purples are not spectral, there is no monochromatic light source able to generate a purple color. Instead, every color on the line of purples is produced by mixing a unique ratio of fully saturated red and fully saturated violet, unlike spectral colors, colors on the line of purples are more difficult to implement practically. In 3-dimensional color spaces the line, if present, becomes a 2-dimensional shape, for example, in CIE XYZ it is a planar sector bounded by black–red and black–violet rays. RGB color model, although theoretically capable to get close to the purple boundary due to its additive nature. The boundary of sRGB goes roughly parallel to the line of purples, connecting primaries red and blue, magenta ink, a CMYKs primary, is also rather distant from the line for the reason explained above. Wide-gamut RGB color space approximates boundary purples better, but corresponding devices are expensive and these color terms mostly do not refer to colors on the line of purples, but there are nearby colors which have slightly less than maximally possible colorfulness
Line of purples
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The line of purples circled on the CIE chromaticity diagram
Color coordinates
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