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This is because with this technology you can print only the needed cards, thus, resulting to orders printed in the exact quantity required. But just the same this kind of printing system is not for everyone. There are risks and changes that need to be dealt with. Nevertheless, the printing industry will continue to change and improve in the years to come. Thus, all business owners and companies have to do is to determine whether this certain printing technique is what they need.
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(Redirected from Indigo Digital Press) HP Indigo building, Nes Ziona, Israel HP Indigo Division, is a company that was first developed and popularized as an Israeli company named Indigo Digital Press that was bought by Hewlett-Packard. It develops, manufactures and markets digital printing solutions, including printing presses, proprietary consumables and workflow. Founded in 1977, it was an independent company until it was acquired by HP in 2001. They have offices around the world, with headquarters in Nes Ziona, Israel. Customers of HP Indigo solutions include commercial printers, photo specialty printers, and label and packaging converters to print applications such as marketing collateral, photo albums, direct mail, labels, folding cartons, flexible packaging, books, manuals, and specialty jobs. The ability of digital presses to print without plates enables the use of variable data such as text or images, such as in personalized direct marketing applications, or in photo albums, which are usually printed in copies of one. Digital presses also make short-run and just-in-time printing cost-effective. In this way, digital presses have changed the economic models for print in a wide variety of market segments, cutting down on supply chain costs and simplifying the creation of campaigns that reach consumers in more creative, personalized ways. The name Indigo comes from a company formed by Benny Landa in 1977. Landa, known as the father of digital offset color printing, was born in Poland to post-World War II Jewish refugee parents, who later immigrated to Edmonton, Alberta, Canada. Landa's interest in printing goes back to the time he worked as a child in his father's photo shop. His father purchased a cigar store that had a small photo studio in the back which he developed, using his skills as a carpenter, into his own portrait studio. While a student in London, Landa got a job at Commercial Aid Printing Services (CAPS), a company offering printing services and microfilm solutions. Landa was instrumental in developing a solution that won the company a contract with Rolls Royce and was appointed as Head of R&D. However, CAPS lacked manufacturing capital and went into receivership in 1969. In 1971 he joined Gerald Frankel, the owner of CAPS, and founded a new company - Imaging Technology (Imtec). Landa led Imtec’s R&D activities and invented the company’s core imaging technology. While researching liquid toners at Imtec, he worked on a method of high-speed image development that would later lead to the invention of ElectroInk. At the start of the 1990s Indigo moved from a primarily research-driven business into a full-scale printing equipment manufacturing company. The company's first product would be a digital plotter/duplicator, bringing the tiny company (its 1991 sales totaled less than US$5 million, generating a profit of $440,000) head to head with such industry giants as Xerox and Canon. In 1993 Indigo launched the E-Print 1000 at IPEX trade show. The E-Print 1000 eliminated the expense and labor of the plate-printing setup process, printing directly from a computer file, and enabled inexpensive short-run color printing. Images not only could be readily changed, they could be changed from page to page, requiring neither additional setup or pauses in the print run. Instead of printing to metal plates, the E-Print created a latent image on the Photo Imaging Plate or PIP through the use of an electrostatic charge. This charged area would then attract the charged ElectroInk, which would in turn be transferred to the ITM or blanket, and then again transfer from the blanket to the paper or other substrate. Because 100% of the ink transfers from PIP to blanket to substrate, a different image and color could be printed with each rotation of the press. At the same time, Indigo's ElectroInk-based color inks offered print quality rivaling that of traditional printing processes. Almost 20 years later, and despite the numerous technological improvements, Indigo presses are still based on this core technology. In 1994 Indigo had an initial public offering on the NASDAQ stock exchange, selling 52 million shares at $20 per share and raising $100 million. The offering reduced Landa's personal holding in Indigo to 70 percent. As the stock continued to climb, the following year, Landa's paper worth reached some $2 billion by 1995. At the drupa trade show in 1995 Indigo launched another product: the Omnius press. Whereas E-Print focused on medium-volume single-sheet printing, Omnius brought digital printing to a variety of surfaces, including plastic, cardboard, film, and, especially, cans, bottles, and other packaging surfaces. Omnius was the precursor of today's portfolio of Indigo's labels and packaging presses. At the end of 1995, Indigo sales did not reach the expected levels, and the company found itself overstaffed. Despite a strong rise in revenues to $165 million, the company posted its fourth year of losses, of about $40 million. George Soros however still believed in the company’s potential and increased his investment to 30 percent of Indigo's shares by 1997. By 1998 the company improved its financial performance and revenues passed the $200 million mark for the first time. Hewlett-Packard offices in Nes Ziona In 2000 the Hewlett-Packard company made a $100m investment in Indigo, buying 14.8 million of Indigo's common shares, which represented 13.4 percent of the company's outstanding shares. On September 6, 2001, HP announced that it would acquire the remaining outstanding shares of Indigo Indigo N.V. (NASDAQ: INDG) for approximately $629 million in HP common stock and a potential future cash payment of up to $253 million contingent upon Indigo's achievement of long-term revenue goals, for an aggregate potential payment of up to $882 million.  In the following years, HP continued to invest in Israel-based graphic arts companies, acquiring Scitex Vision in 2005 and Nur Macroprinters in 2007. Other employees of HP in Israel (which includes not only employees of the Indigo division, but also of Scitex and Israeli's divisions of HP Labs, made it the second-largest foreign employer after Intel. Under the ownership of HP, Indigo developed and grew to become a world leader in the digital print industry. In 2002 they announced the first product manufactured jointly with HP: the HP Indigo 5000, and their second generation of products (known internally as "series 2") was born. Other products belonging to these series were the roll-fed ws4000 series. At drupa 2008 Indigo announced the Indigo 7000 digital press, with over 70% higher productivity over series 2. This product further pushed the break-even point versus offset lithography and enabled more pages to be economically viable on Indigo. Other presses unveiled at drupa included the double engine Indigo W7200 and the new derivative for labels, the Indigo WS6000. In August 2009 HP announced they had reached 5,000 HP Indigo digital presses in operation around the world. The company is ranked No. 1 in the US high-volume digital press market and, according to HP officials, has a 75% share of the world market for digital commercial photo printing. In March 2012 HP Indigo unveiled the Indigo 10000 B2/29" digital press and released it to market a year later. By March 2016, there were over 200 Indigo 10000 customer installations in over 20 countries. In September 2013, Indigo claimed dominance of the narrow label market, with General Manager Alon Bar-Shany calling the Indigo WS6600 press "the best-selling solution in the narrow web industry, not just in digital printing, (but) narrow overall."  In 2014, HP Indigo marked the launch of the new 20000 and 30000 digital presses, aimed at the packaging markets. The presses target flexible packaging converters, label converters and folding carton establishments. In 2016 Indigo announced a new portfolio based on innovation on four core pillars of their technology: quality, color, applications and productivity. They also announced PrintOS, a cloud-based platform to help customers. HP Indigo uses a proprietary, patented technology and a business model that sells both presses and their consumables, as well as services. The presses are assembled in a dedicated facility in HP's Kiryat Gat campus, and the inks are manufactured in both Kiryat Gat and TUAS, Singapore. Indigo has over 4500 customers in 120 countries around the world. They include some of the largest names in print world, including Cimpress and Consolidated Graphics (now part of RR Donnelley) but also a widevariety of small and medium-sized print service providers and labels and packaging converters. According to Indigo GM Alon Bar-Shany, volume printed on Indigo presses grew by over 50% from 2012 to 2016, reaching an estimated 30 B pages. The year 2005 marked the creation of Dscoop, the independent user's group of Indigo and HP Graphic Arts solutions. By 2015 it reached over 7000 users today, including owners and technical personnel. Dscoop membership is free of charge for HP Graphic Arts users throughout the Americas, Europe, the Middle East and Africa, Asia Pacific and Japan. There are several families of HP Indigo presses, which can be broadly grouped by the type of paper-handling mechanism they work with: Sheetfed (or cut-sheet) or Webfed (or roll-fed). Sheetfed presses print on sheets, have a feeder system consisting of drawers and/or a pallet of paper, and print on both sides of the paper (duplex print/perfecter), printed sheets are collected in a stacker mainly for paper printing. Examples of sheetfed presses include the HP Indigo 7900, the HP Indigo 10000 and the new HP Indigo 12000. Webfed presses print on rolls, often referred to as a web the feeder system (unwinder) feeds the paper through continuously in most cases, print on one side of the substrate (simplex) printed rolls can be collected on a rewinder or cut into sheets (sheeter). Examples of webfed presses are the HP Indigo WS6800 narrow format press for labels and flexible packaging, the Indigo 20000 digital press, and the Indigo W7250 for books, photo and other commercial applications. The launch of the HP Indigo 10000 digital press in 2012 marked the first time the company embarked on a platform that supports a paper size beyond A3. With the B2/29.5" paper format, they aim to increase the productivity and application range of traditional print service providers. In 2014 two new products based in the same type of engine/format were released, the Indigo 20000 and the Indigo 30000, aimed at the flexible packaging and folding-cartons markets, respectively. In 2016, Indigo introduced the 80/minutes per meter roll-fed 80000 press for label production, as well as new models of its sheetfed presses: the 12000, 7900 and 5900. The also announced the B1 roll-fed Indigo 50000, which is scheduled for release in 2017. In addition, the announced new solutions for packaging post-print under the Pack Ready umbrella, and demonstrated a concept for digital combination printing for labels. Each Indigo press has up to 7 color stations, which can use cyan, magenta, yellow, black and a variety of special and spot color inks, such as white, silver, UV red and transparent. HP provides the option for users to mix their own ink colors to match Pantone references. This is common with non-digital offset litho presses, and is one of the features that distinguishes the HP Indigo process. "Off-press" colors are mixed from 11 color (from the 15 original) Pantone spectrum at an offline, ink mixing station. Users can also order special pre-mixed colors from HP Indigo, for example fluorescent pink. HP Indigo presses are available in configurations supporting four, five, six or seven colors. At drupa 2008, Indigo unveiled a new workflow strategy for their portfolio called HP SmartStream, based on their own development and on partnerships with other industry vendors. Among the announcements was a [web-to-print] product in partnership with Press-Sense (later bought by Bitstream makers of Pageflex.) They also released new versions of their Digital Front Ends (DFEs). Today, their SmartStream workflow portfolio is based on both their own products, as well as partnerships with other graphic arts vendors in fields such as job creation, pre-press, variable data printing and finishing. In 2004 HP made a 100 million shekel investment in a new production site in Kiryat Gat, Israel. The factory is responsible for manufacturing HP Indigo ElectroInk. There is a sister facility in Singapore that also manufactures Indigo ElectroInk. In 2007 an adjacent hardware center was opened in Kiryat Gat. This facility assembles frames, feeders, and other components with imaging engines into finished presses, and also serves as the site for manufacturing other operator-replaceable consumables, such as the blanket. In late 2012, HP Indigo inaugurated a second ink plant in Kiryat Gat, which will focus on the manufacturing of ElectroInk for the new family of presses: the HP Indigo 10000, Indigo 20000 and Indigo 30000 digital presses. This 118,000 square feet facility is reported to be the first building in the country and the first HP manufacturing facility worldwide designed to meet the LEED Silver environmental standard. Early incarnations of the press (Series 1 engines) were prone to banding and ink adhesion problems. However newer models have corrected most of these issues.
Printing, Print Color FlyersColored pencils Color effect – Sunlight shining through stained glass onto carpet (Nasir ol Molk Mosque located in Shiraz, Iran) Colors can appear different depending on their surrounding colors and shapes. The two small squares have exactly the same color, but the right one looks slightly darker. Color (American English) or colour (Commonwealth English) 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 cone 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. This reflection is governed by the object's physical properties such as light absorption, emission spectra, etc. By defining a color space, colors can be identified numerically by coordinates. The RGB color space for instance is a color space corresponding to human trichromacy and to the three cone cell types that respond to three bands of light: long wavelengths, peaking near 564–580 nm (red); medium-wavelength, peaking near 534–545 nm (green); and short-wavelength light, near 420–440 nm (blue). 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 colour's colorfulness). The photo-receptivity of the "eyes" of other species also varies considerably from that of humans and so results in correspondingly different color perceptions that cannot readily be compared to one another. Honeybees and bumblebees for instance have trichromatic color vision sensitive to ultraviolet (an electromagnetic radiation with a wavelength from 10 nm (30 PHz) to 400 nm (750 THz), shorter than that of visible light but longer than X-rays) 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 animal kingdom has been found in stomatopods (such as the mantis shrimp) 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. 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 (that is, what is commonly referred to simply as light). Continuous optical spectrum rendered into the sRGB color space. Electromagnetic radiation is characterized by its wavelength (or frequency) and its intensity. When the wavelength is within the visible spectrum (the range of wavelengths humans can perceive, approximately from 390 nm to 700 nm), it is known as "visible light". Most light sources emit light at many different wavelengths; a source's 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, there are many more possible spectral combinations than color sensations. In fact, one may formally define a color as a class of spectra that give rise to the same color sensation, although such classes would vary widely among different species, and to a lesser extent among individuals within the same species. In each such class the members are called metamers of the color in question. The familiar colors of the rainbow in the spectrum – named using the Latin word for appearance or apparition by Isaac Newton in 1671 – include all those colors that can be produced by visible light of a single wavelength only, the pure spectral or monochromatic colors. The table at right shows approximate frequencies (in terahertz) and wavelengths (in nanometers) for various pure spectral colors. The wavelengths listed are as measured in air or vacuum (see refractive index). The color table should not be interpreted as a definitive list – the pure spectral colors form a continuous spectrum, and how it is divided into distinct colors linguistically is a matter of culture and historical contingency (although people everywhere have been shown to perceive colors in the same way). A common list identifies six main bands: red, orange, yellow, green, blue, and violet. Newton's 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, and that indigo was simply the dark blue of the indigo dye that was being imported at the time. The intensity of a spectral color, relative to the context in which it is viewed, may alter its perception considerably; for example, a low-intensity orange-yellow is brown, and a low-intensity yellow-green is olive-green. 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. Physically, objects can be said to have the color of the light leaving their surfaces, which normally depends on the spectrum of the incident illumination and the reflectance properties of the surface, as well as potentially on the angles of illumination and viewing. Some objects not only reflect light, but also transmit light or emit light themselves, which also contribute to the color. A viewer's perception of the object's color depends not only on the spectrum of the light leaving its surface, but also on a host of contextual cues, so that color differences between objects can be discerned mostly independent of the lighting spectrum, viewing angle, etc. This effect is known as color constancy. The upper disk and the lower disk have exactly the same objective color, and are in identical gray surroundings; based on context differences, humans perceive the squares as having different reflectances, and may interpret the colors as different color categories; see checker shadow illusion. Some generalizations of the physics can be drawn, neglecting perceptual effects for now: To summarize, the color of an object is a complex result of its surface properties, its transmission properties, and its emission properties, all of which contribute to the mix of wavelengths in the light leaving the surface of the object. The perceived color is then further conditioned by the nature of the ambient illumination, and by the color properties of other objects nearby, and via other characteristics of the perceiving eye and brain. When viewed in full size, this image contains about 16 million pixels, each corresponding to a different color on the full set of RGB colors. The human eye can distinguish about 10 million different colors. Main article: Color theory Although Aristotle and other ancient scientists had already written on the nature of light and color vision, it was not until Newton that light was identified as the source of the color sensation. In 1810, Goethe published his comprehensive Theory of Colors in which he ascribed physiological effects to color that are now understood as psychological. In 1801 Thomas Young proposed his trichromatic theory, based on the observation that any color could be matched with a combination of three lights. This theory was later refined by James Clerk Maxwell and Hermann von Helmholtz. As Helmholtz puts it, "the principles of Newton's law of mixture were experimentally confirmed by Maxwell in 1856. Young's theory of color sensations, like so much else that this marvelous investigator achieved in advance of his time, remained unnoticed until Maxwell directed attention to it." At the same time as Helmholtz, Ewald Hering developed the opponent process theory of color, noting that color blindness and afterimages typically come in opponent pairs (red-green, blue-orange, yellow-violet, and black-white). Ultimately these two theories were synthesized in 1957 by Hurvich and Jameson, who showed that retinal processing corresponds to the trichromatic theory, while processing at the level of the lateral geniculate nucleus corresponds to the opponent theory. In 1931, an international group of experts known as the Commission internationale de l'éclairage (CIE) developed a mathematical color model, which mapped out the space of observable colors and assigned a set of three numbers to each. Main article: Color vision Normalized typical human cone cell responses (S, M, and L types) to monochromatic spectral stimuli The ability of the human eye to distinguish colors is based upon the varying sensitivity of different cells in the retina to light of different wavelengths. Humans are trichromatic—the retina contains three types of color receptor cells, or cones. One type, relatively distinct from the other two, is most responsive to light that is perceived as blue or blue-violet, with wavelengths around 450 nm; cones of this type are sometimes called short-wavelength cones, S cones, or blue cones. The other two types are closely related genetically and chemically: middle-wavelength cones, M cones, or green cones are most sensitive to light perceived as green, with wavelengths around 540 nm, while the long-wavelength cones, L cones, or red cones, are most sensitive to light is perceived as greenish yellow, with wavelengths around 570 nm. Light, no matter how complex its composition of wavelengths, is reduced to three color components by the eye. Each cone type adheres to the Principle of Univariance, which is that each cone's output is determined by the amount of light that falls on it over all wavelengths. For each location in the visual field, the three types of cones yield three signals based on the extent to which each is stimulated. These amounts of stimulation are sometimes called tristimulus values. The response curve as a function of wavelength varies for each type of cone. Because the curves overlap, some tristimulus values do not occur for any incoming light combination. For example, it is not possible to stimulate only the mid-wavelength (so-called "green") cones; the other cones will inevitably be stimulated to some degree at the same time. The set of all possible tristimulus values determines the human color space. It has been estimated that humans can distinguish roughly 10 million different colors. The other type of light-sensitive cell in the eye, the rod, has a different response curve. In normal situations, when light is bright enough to strongly stimulate the cones, rods play virtually no role in vision at all. On the other hand, in dim light, the cones are understimulated leaving only the signal from the rods, resulting in a colorless response. (Furthermore, the rods are barely sensitive to light in the "red" range.) In certain conditions of intermediate illumination, the rod response and a weak cone response can together result in color discriminations not accounted for by cone responses alone. These effects, combined, are summarized also in the Kruithof curve, that describes the change of color perception and pleasingness of light as function of temperature and intensity. Main article: Color vision The visual dorsal stream (green) and ventral stream (purple) are shown. The ventral stream is responsible for color perception. While the mechanisms of color vision at the level of the retina are well-described in terms of tristimulus values, color processing after that point is organized differently. A dominant theory of color vision proposes that color information is transmitted out of the eye by three opponent processes, or opponent channels, each constructed from the raw output of the cones: a red–green channel, a blue–yellow channel, and a black–white "luminance" channel. This theory has been supported by neurobiology, and accounts for the structure of our subjective color experience. Specifically, it explains why humans cannot perceive a "reddish green" or "yellowish blue", and it predicts the color wheel: it is the collection of colors for which at least one of the two color channels measures a value at one of its extremes. The exact nature of color perception beyond the processing already described, and indeed the status of color as a feature of the perceived world or rather as a feature of our perception of the world – a type of qualia – is a matter of complex and continuing philosophical dispute. Main article: Color blindness If one or more types of a person's color-sensing cones are missing or less responsive than normal to incoming light, that person can distinguish fewer colors and is said to be color deficient or color blind (though this latter term can be misleading; almost all color deficient individuals can distinguish at least some colors). Some kinds of color deficiency are caused by anomalies in the number or nature of cones in the retina. Others (like central or cortical achromatopsia) are caused by neural anomalies in those parts of the brain where visual processing takes place. Main article: Tetrachromacy While most humans are trichromatic (having three types of color receptors), many animals, known as tetrachromats, have four types. These include some species of spiders, most marsupials, birds, reptiles, and many species of fish. Other species are sensitive to only two axes of color or do not perceive color at all; these are called dichromats and monochromats respectively. A distinction is made between retinal tetrachromacy (having four pigments in cone cells in the retina, compared to three in trichromats) and functional tetrachromacy (having the ability to make enhanced color discriminations based on that retinal difference). As many as half of all women are retinal tetrachromats.:p.256 The phenomenon arises when an individual receives two slightly different copies of the gene for either the medium- or long-wavelength cones, which are carried on the X chromosome. To have two different genes, a person must have two X chromosomes, which is why the phenomenon only occurs in women. There is one scholarly report that confirms the existence of a functional tetrachromat. In certain forms of synesthesia/ideasthesia, perceiving letters and numbers (grapheme–color synesthesia) or hearing musical sounds (music–color synesthesia) will lead to the unusual additional experiences of seeing colors. Behavioral and functional neuroimaging experiments have demonstrated that these color experiences lead to changes in behavioral tasks and lead to increased activation of brain regions involved in color perception, thus demonstrating their reality, and similarity to real color percepts, albeit evoked through a non-standard route. After exposure to strong light in their sensitivity range, photoreceptors of a given type become desensitized. For a few seconds after the light ceases, they will continue to signal less strongly than they otherwise would. Colors observed during that period will appear to lack the color component detected by the desensitized photoreceptors. This effect is responsible for the phenomenon of afterimages, in which the eye may continue to see a bright figure after looking away from it, but in a complementary color. Afterimage effects have also been utilized by artists, including Vincent van Gogh. Main article: Color constancy When an artist uses a limited color palette, the eye tends to compensate by seeing any gray or neutral color as the color which is missing from the color wheel. For example, in a limited palette consisting of red, yellow, black, and white, a mixture of yellow and black will appear as a variety of green, a mixture of red and black will appear as a variety of purple, and pure gray will appear bluish. The trichromatic theory is strictly true when the visual system is in a fixed state of adaptation. In reality, the visual system is constantly adapting to changes in the environment and compares the various colors in a scene to reduce the effects of the illumination. If a scene is illuminated with one light, and then with another, as long as the difference between the light sources stays within a reasonable range, the colors in the scene appear relatively constant to us. This was studied by Edwin Land in the 1970s and led to his retinex theory of color constancy. It should be noted, that both phenomena are readily explained and mathematically modeled with modern theories of chromatic adaptation and color appearance (e.g. CIECAM02, iCAM). There is no need to dismiss the trichromatic theory of vision, but rather it can be enhanced with an understanding of how the visual system adapts to changes in the viewing environment. Main article: Color term See also: Lists of colors and Web colors Colors vary in several different ways, including hue (shades of red, orange, yellow, green, blue, and violet), saturation, brightness, and gloss. Some color words are derived from the name of an object of that color, such as "orange" or "salmon", while others are abstract, like "red". In the 1969 study Basic Color Terms: Their Universality and Evolution, Brent Berlin and Paul Kay describe a pattern in naming "basic" colors (like "red" but not "red-orange" or "dark red" or "blood red", which are "shades" of red). All languages that have two "basic" color names distinguish dark/cool colors from bright/warm colors. The next colors to be distinguished are usually red and then yellow or green. All languages with six "basic" colors include black, white, red, green, blue, and yellow. The pattern holds up to a set of twelve: black, gray, white, pink, red, orange, yellow, green, blue, purple, brown, and azure (distinct from blue in Russian and Italian, but not English). Individual colors have a variety of cultural associations such as national colors (in general described in individual color articles and color symbolism). The field of color psychology attempts to identify the effects of color on human emotion and activity. Chromotherapy is a form of alternative medicine attributed to various Eastern traditions. Colors have different associations in different countries and cultures. Different colors have been demonstrated to have effects on cognition. For example, researchers at the University of Linz in Austria demonstrated that the color red significantly decreases cognitive functioning in men. The CIE 1931 color space chromaticity diagram. The outer curved boundary is the spectral (or monochromatic) locus, with wavelengths shown in nanometers. The colors depicted depend on the color space of the device on which you are viewing the image, and therefore may not be a strictly accurate representation of the color at a particular position, and especially not for monochromatic colors. Most light sources are mixtures of various wavelengths of light. Many such sources can still effectively produce a spectral color, as the eye cannot distinguish them from single-wavelength sources. For example, most computer displays reproduce the spectral color orange as a combination of red and green light; it appears orange because the red and green are mixed in the right proportions to allow the eye's cones to respond the way they do to the spectral color orange. A useful concept in understanding the perceived color of a non-monochromatic light source is the dominant wavelength, which identifies the single wavelength of light that produces a sensation most similar to the light source. Dominant wavelength is roughly akin to hue. There are many color perceptions that by definition cannot be pure spectral colors due to desaturation or because they are purples (mixtures of red and violet light, from opposite ends of the spectrum). Some examples of necessarily non-spectral colors are the achromatic colors (black, gray, and white) and colors such as pink, tan, and magenta. Two different light spectra that have the same effect on the three color receptors in the human eye will be perceived as the same color. They are metamers of that color. This is exemplified by the white light emitted by fluorescent lamps, which typically has a spectrum of a few narrow bands, while daylight has a continuous spectrum. The human eye cannot tell the difference between such light spectra just by looking into the light source, although reflected colors from objects can look different. (This is often exploited; for example, to make fruit or tomatoes look more intensely red.) Similarly, most human color perceptions can be generated by a mixture of three colors called primaries. This is used to reproduce color scenes in photography, printing, television, and other media. There are a number of methods or color spaces for specifying a color in terms of three particular primary colors. Each method has its advantages and disadvantages depending on the particular application. No mixture of colors, however, can produce a response truly identical to that of a spectral color, although one can get close, especially for the longer wavelengths, where the CIE 1931 color space chromaticity diagram has a nearly straight edge. For example, mixing green light (530 nm) and blue light (460 nm) produces cyan light that is slightly desaturated, because response of the red color receptor would be greater to the green and blue light in the mixture than it would be to a pure cyan light at 485 nm that has the same intensity as the mixture of blue and green. Because of this, and because the primaries in color printing systems generally are not pure themselves, the colors reproduced are never perfectly saturated spectral colors, and so spectral colors cannot be matched exactly. However, natural scenes rarely contain fully saturated colors, thus such scenes can usually be approximated well by these systems. The range of colors that can be reproduced with a given color reproduction system is called the gamut. The CIE chromaticity diagram can be used to describe the gamut. Another problem with color reproduction systems is connected with the acquisition devices, like cameras or scanners. The characteristics of the color sensors in the devices are often very far from the characteristics of the receptors in the human eye. In effect, acquisition of colors can be relatively poor if they have special, often very "jagged", spectra caused for example by unusual lighting of the photographed scene. A color reproduction system "tuned" to a human with normal color vision may give very inaccurate results for other observers. The different color response of different devices can be problematic if not properly managed. For color information stored and transferred in digital form, color management techniques, such as those based on ICC profiles, can help to avoid distortions of the reproduced colors. Color management does not circumvent the gamut limitations of particular output devices, but can assist in finding good mapping of input colors into the gamut that can be reproduced. Additive color mixing: combining red and green yields yellow; combining all three primary colors together yields white. Additive color is light created by mixing together light of two or more different colors. Red, green, and blue are the additive primary colors normally used in additive color systems such as projectors and computer terminals. Subtractive color mixing: combining yellow and magenta yields red; combining all three primary colors together yields black Subtractive coloring uses dyes, inks, pigments, or filters to absorb some wavelengths of light and not others. The color that a surface displays comes from the parts of the visible spectrum that are not absorbed and therefore remain visible. Without pigments or dye, fabric fibers, paint base and paper are usually made of particles that scatter white light (all colors) well in all directions. When a pigment or ink is added, wavelengths are absorbed or "subtracted" from white light, so light of another color reaches the eye. If the light is not a pure white source (the case of nearly all forms of artificial lighting), the resulting spectrum will appear a slightly different color. Red paint, viewed under blue light, may appear black. Red paint is red because it scatters only the red components of the spectrum. If red paint is illuminated by blue light, it will be absorbed by the red paint, creating the appearance of a black object. Further information: Structural coloration and Animal coloration Structural colors are colors caused by interference effects rather than by pigments. Color effects are produced when a material is scored with fine parallel lines, formed of one or more parallel thin layers, or otherwise composed of microstructures on the scale of the color's wavelength. If the microstructures are spaced randomly, light of shorter wavelengths will be scattered preferentially to produce Tyndall effect colors: the blue of the sky (Rayleigh scattering, caused by structures much smaller than the wavelength of light, in this case air molecules), the luster of opals, and the blue of human irises. If the microstructures are aligned in arrays, for example the array of pits in a CD, they behave as a diffraction grating: the grating reflects different wavelengths in different directions due to interference phenomena, separating mixed "white" light into light of different wavelengths. If the structure is one or more thin layers then it will reflect some wavelengths and transmit others, depending on the layers' thickness. Structural color is studied in the field of thin-film optics. A layman's term that describes particularly the most ordered or the most changeable structural colors is iridescence. Structural color is responsible for the blues and greens of the feathers of many birds (the blue jay, for example), as well as certain butterfly wings and beetle shells. Variations in the pattern's spacing often give rise to an iridescent effect, as seen in peacock feathers, soap bubbles, films of oil, and mother of pearl, because the reflected color depends upon the viewing angle. Numerous scientists have carried out research in butterfly wings and beetle shells, including Isaac Newton and Robert Hooke. Since 1942, electron micrography has been used, advancing the development of products that exploit structural color, such as "photonic" cosmetics. Find more aboutColorat Wikipedia's sister projects
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