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"Color separation" redirects here. For other uses, see Chroma key. Chroma Key is the name under which ex- Dream Theater Keyboardist Kevin Moore records

Color (colour[1]) printing is the reproduction of an image or text in color (as opposed to simpler black and white or monochrome printing). Monochrome comes from the Greek μονόχρωμος ( monochromos) meaning “of one color” which is a combination

While there are many techniques for reproducing images in color, specific graphic processes and industrial equipment are used for mass reproduction of color images on paper. In this sense, "color printing" involves reproduction techniques suited for printing presses capable of thousands or millions of impressions for publishing newspapers and magazines, brochures, cards, posters and similar mass-market items.

In this type of industrial or commercial printing, the technique used to print full-color images, such as color photographs, is referred to as four-color-process printing, because four inks are used: three primary colors plus black. The "subtractive" primary ink colors are cyan, a bright blue; magenta, a vivid red-purple; and yellow; which are abbreviated as CMYK. CMYK (short for '''c'''yan, '''m'''agenta, '''y'''ellow, and k ey ( Black) and often referred to as process color

Two graphic techniques are required to prepare images for four-color printing. In the "pre-press" stage, original images are translated into forms that can be used on a printing press, through "color separation" and "screening" or "halftoning. " These steps make possible the creation of printing plates that can transfer color impressions to paper on printing presses based on the principles of lithography. Lithography is a method for Printing using a plate or stone with a completely smooth surface

An emerging method of full-color printing is six-color process printing (for example, Pantone's Hexachrome system) which adds orange and green to the traditional CMYK inks for a larger and more vibrant gamut, or color range. Pantone Inc is a corporation headquartered in Carlstadt, New Jersey, USA Hexachrome is Pantone 's six-color Color printing process In addition to custom CMYK inks Hexachrome adds orange and Green inks to In color reproduction including Computer graphics and Photography, the gamut, or color gamut (pronounced /ˈgæmət/ is a certain complete However, such alternate color systems still rely on color separation, halftoning and lithography to produce printed images.

Color printing can also involve as few as one color ink, or multiple color inks which are not the primary colors. Using a limited number of color inks, or specific color inks in addition to the primary colors, is referred to as "spot color" printing. Generally, spot-color inks are specific formulations that are designed to print alone, rather than to blend with other inks on the paper to produce various hues and shades. The range of available spot color inks, much like paint, is nearly unlimited, and much more varied than the colors that can be produced by four-color-process printing. Spot-color inks range from subtle pastels to intense fluorescents to reflective metallics.

Color printing involves a series of steps, or transformations, to generate a quality color reproduction. The following sections focus on the steps used when reproducing a color image in CMYK printing, along with some historical perspective.

Contents

Color separation process

The process of color separation starts by separating the original artwork into red, green, and blue components (for example by a digital scanner). Before digital imaging was developed, the traditional method of doing this was to photograph the image three times, using a filter for each color. Digital imaging or digital image acquisition is the creation of Digital images typically from a physical object Photography (fә'tɒgrәfi or fә'tɑːgrәfi (from Greek φωτο and γραφία is the process and Art of recording pictures by means of capturing However this is achieved, the desired result is three grayscale images, which represent the red, green, and blue (RGB) components of the original image:

The next step is to invert each of these separations. When a negative image of the red component is produced, the resulting image represents the cyan component of the image. Likewise, negatives are produced of the green and blue components to produce magenta and yellow separations, respectively. This is done because cyan, magenta, and yellow are subtractive primaries which each represent two of the three additive primaries (RGB) after one additive primary has been subtracted from white light. A subtractive color model explains the mixing of Paints Dyes Inks and natural colorants to create a range of Colors where each such color An additive color model involves Light emitted directly from a source or illuminant of some sort


Cyan, magenta, and yellow are the three main pigments used for color reproduction. When these three colors are combined in printing, the result should be a reasonable reproduction of the original, but in practice this is not the case. Due to limitations in the ink pigments, the darker colors are dirty and muddied. An ink is a Liquid containing various Pigments and/or Dyes used for coloring a surface to produce an Image, text, or For the drug referred to as "pigment" see Black tar heroin. To resolve this, a black separation is also created, which improves the shadow and contrast of the image. Numerous techniques exist to derive this black separation from the original image; these include grey component replacement, under color removal, and under color addition. Within the CMY color space any hue angle can be achieved by combining two of the three primaries In Four-color printing (or more under color removal (UCR is the process of eliminating amounts of Yellow, Magenta, and Cyan that would have In Four-color printing (or more under color addition ( UCA) is a technique for darkening areas of the printed image by adding colored inks This printing technique is referred to as CMYK (the "K" being short for "key. CMYK (short for '''c'''yan, '''m'''agenta, '''y'''ellow, and k ey ( Black) and often referred to as process color " In this case, the key color is black).

Today's digital printing methods do not have the restriction of a single color space that traditional CMYK processes do. A Color model is an abstract mathematical model describing the way Colors can be represented as Tuples of numbers typically as three or four values or color components Many presses can print from files that were ripped with images using either RGB or CMYK modes. The color reproduction abilities of a particular color space can vary; the process of obtaining accurate colors within a color model is called color matching.

Screening

Inks used in color printing presses are semi-transparent and can be printed on top of each other to produce different hues. For example, green results from printing yellow and cyan inks on top of each other. However, a printing press cannot vary the amount of ink applied except through "screening," a process that represents lighter shades as tiny dots, rather than solid areas, of ink. This is analogous to mixing white paint into a color to lighten it, except the white is the paper itself. In process color printing, the screened image, or halftone for each ink color is printed in succession. Halftone is the Reprographic technique that simulates Continuous tone imagery through the use of equally spaced dots of varying size The screen grids are set at different angles, and the dots therefore create tiny rosettes, which, through a kind of optical illusion, appear to form a continuous-tone image. This article is about visual perception See Optical Illusion (Album for information about the Time Requiem album You can view the halftone screens that create printed images under magnification.

Traditionally, halftone screens were generated by inked lines on two sheets of glass that were cemented together at right angles. In Geometry and Trigonometry, a right angle is an angle of 90 degrees corresponding to a quarter turn (that is a quarter of a full circle Each of the color separation films were then exposed through these screens. The resulting high-contrast image, once processed, had dots of varying diameter depending on the amount of exposure that area received, which was modulated by the grayscale separation film image.

The glass screens were made obsolete by high-contrast films where the halftone dots were exposed with the separation film. This in turn was replaced by a process where the halftones are electronically generated directly on the film with a laser. Most recently, computer to plate (CTP) technology has allowed printers to bypass the film portion of the process entirely. Computer to plate (CTP is an Imaging technology used in modern printing processes. CTP images the dots directly on the printing plate with a laser, saving money, increasing quality (by reducing the repeated generations), reducing lead-times, and saving the environment from toxic film-processing chemicals.

Screens with a "frequency" of 60 to 120 lines per inch (lpi) reproduce color photographs in newspapers. The coarser the screen (lower frequency), the lower the quality of the printed image. Highly absorbent newsprint requires a lower screen frequency than less-absorbent coated paper stock used in magazines and books, where screen frequencies of 133 to 200 lpi and higher are used.

The measure of how much an ink dot spreads and becomes larger on paper is called dot gain. Dot gain is a phenomenon in Printing and Graphic arts whereby printed dots are perceived and actually printed bigger than intended This phenomenon must be accounted for in photographic or digital preparation of screened images. Dot gain is higher on more absorbent, uncoated paper stock such as newsprint.

References

  1. ^ See American and British English spelling differences. American and British English spelling differences are one aspect of American and British English differences.

See also

External links

Printing is a process for reproducing text and image typically with ink on Paper using a printing press Letterpress printing is a term for Printing text with Movable type, in which the raised surface of the type is Inked and then pressed against a smooth For the use of the technique in art see Woodcut on the technique and Old master print for the history in Europe and Woodblock printing in Japan. Flexography (also called surface printing) often abbreviated to flexo, is a method of Printing most commonly used for packaging (labels tape bags Intaglio (pronounced in-TAL-yo ɪn'tælɪəʊ is a family of Printmaking techniques in which the image is incised into a surface known as the matrix or plate Lithography is a method for Printing using a plate or stone with a completely smooth surface Offset printing is a commonly used Printing technique where the Inked image is transferred (or "offset" from a plate to a rubber blanket then to the Gravure may also refer to Gravure idol. Rotogravure ( roto or gravure for short is a type of intaglio Printing Typography is the art and techniques of arranging type, Type design, and modifying type Glyphs Type glyphs are created and modified using a variety
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