page_title: Color printing
section_title: Color separation process
hierarchical_section_title: Color printing / Modern process / Color separation process
caption_attribution_description: English: Still-life of fruit. One of the first images printed using a three-color halftone process that was widely reproduced. Caption reads: "Naturfarbendruck. Aufnahme nach der Natur und Autotypie von W. Kurtz. In drei Farben auf der Buchdruck-Schnellpress von Bartlett &amp; Co., in New York gedruckt." ("Natural-color printing. Admission from nature by W. Kurtz and autotype. Printed in three colors on the printing press of quick Bartlett &amp; Co., in New York.")
context_page_description: Color printing or colour printing is the reproduction of an image or text in color. Any natural scene or color photograph can be optically and physiologically dissected into three primary colors, red, green and blue, roughly equal amounts of which give rise to the perception of white, and different proportions of which give rise to the visual sensations of all other colors. The additive combination of any two primary colors in roughly equal proportion gives rise to the perception of a secondary color. For example, red and green yields yellow, red and blue yields magenta, and green and blue yield cyan. Only yellow is counter-intuitive.
  Yellow, cyan and magenta are merely the "basic" secondary colors: unequal mixtures of the primaries give rise to perception of many other colors all of which may be considered "tertiary."
context_section_description: Typically color separation is the responsibility of the color separator. This includes cleaning up the file to make it print ready and creating a proof for the prepress approval 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. 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.
  Cyan, magenta, and yellow are the three basic colors used for color reproduction. When these three colors are variously used 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 inks, the darker colors are dirty and muddied. 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. This printing technique is referred to as CMYK (the "K" stands for key, a traditional word for the black printing plate).
  Today's digital printing methods do not have the restriction of a single color space that traditional CMYK processes do. 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.
caption: The first widely reproduced image printed using the three-color process, by William Kurtz (January 1893)
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