CMYK color model

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CMYK colors according to DIN 2846-1

CMYK separation:
1. C yan (C),
2. M agenta (M),
3. Y ellow (Y),
4. K ey (K),
5. CM ,
6. CMY ,
7. CMYK

The CMYK color model is a subtractive color model that forms the technical basis for modern four-color printing . The English-language abbreviation CMYK , which is also used in many non-English-speaking countries, stands for the three color components cyan , magenta , yellow and the black component , which is traditionally referred to as the key . The mapping of the CMYK color model to a color space is determined by color profiles.

Basics

etymology

The origin of the naming of the black portion with "K" cannot be clearly etymologically derived. Standard works of four-color printing state that the "K" in the abbreviation CMYK comes from the use of a "key plate " ( K ey plate) in printing . This is the black printing plate , on which the three-color printing plates in the register to be aligned. For the designation of the alignment of the printing plates in this context, however, the term register is used. The term "key" is derived logically nor of the plate printing, but is considerably older: Already in 1843 it was in rotary printing presses used with lag bolts ( screw keys to regulate) the amount of color - a similar offset printing mechanism. There is no reference to the black color. An alternative explanation leads to the inventor of three-color and four-color printing, Jakob Christoph Le Blon . With him, the blue color took a comparable position in the process as black in four-color printing, namely the color to which the others align themselves. Nevertheless, Le Blon abbreviated blue in three-color printing not with “K” but with “B”. A last origin interpretation experimental notes that by using the "K" s instead of the letter "B" ( " B confusion with the color blue (paint") is the probability blue ) are prevented, so that the "K" traditional pragmatic reasons Has.

The sequence of letters "CMYK" does not dictate the order in which the colors are printed or how they are aligned with one another. Mostly the alphabetical order for the three color components is preferred. Other spellings are common such as the reverse alphabetical YMCK. This notation usually corresponds to the color assignments in four-color printing machines, if you look at them along the paper path: white paper, K, then C, then M and finally Y, then the motif is completed. In principle, all spellings are possible, but CMYK is mostly used as the industry standard in the international graphics industry.

ISO scale (Euroscale)

Industrial color printing with CMYK colors will print after Euro scale named because it is the color scheme of the former European scale oriented. This term is used colloquially (especially in the USA as Euroscale ) for European offset printing. The Euroscale is not a correct norm; the correct name for this is ISO scale . The associated standard ISO 2846 defines the properties of these colors for color suppliers. In the ISO 12647 -2 the color effect of these inks is described on different printing papers. For the practical application of this standard, there are ICC profiles , for example “ISO Coated sb” for printing on coated papers .

Color theory

CMY colors with 20% gradation jumps, for K = 0

CMY color space and CMYK color model

The CMYK color model is a generative color model ; it describes the technical mixing ratios of its four basic colors regardless of which basic colors (color valences) are ultimately used. The possible values ​​for each of the four individual colors are between 0% and 100%. 0% stands for unprinted and 100% for a full-tone area .

In order to produce color-accurate print results, these were standardized with the ISO standards 15929 and 15930. PDF / X-3 has established itself as the (minimal) standard in the European printing industry . In North America, the somewhat less restrictive PDF / X-1a format is standard. For color-accurate prints, each individual component (e.g. digicam, scanner, monitor, printer driver, ink, paper) must be profiled .

The "CMY colors" illustration shows the CMY colors in 20 percent gradation jumps. The graphic is in PDF / X-3 format. For the CMYK color model, four standardized color tones are used, which are called process cyan, process magenta, process yellow (also Euro yellow) and process black.

Black structure

The additional printing color black ( key ), for which the CMYK color model was designed, is necessary for the printing together of the three hues , as these theoretically, but not practically, result in a sufficiently deep black. The basic colors of the CMY color space stand for the subtractive color model , as it describes the behavior of light. For the cyan, magenta and yellow pigments that can be used in printing, there are no colorants that have the necessary optical properties of an optimal color . On the other hand, black is absolutely necessary for the achromatic structure of an image. It is used in the separation determines the image in order to avoid the need to print too much color on each other. Hence: the real absorption properties of pigments for printing inks do not permit such a mixture that with three basic colors actually results in a deep black. Pigments do not result in a uniform extinction of the intensities, but (at best) a dark brown. In practice, the pigment carbon black is used for a pure, deep black . In addition, the natural red tint is usually fined with reflex blue. Black is used in four-color printing to improve the contrast in dark parts of an image or drawing. In addition, the colorimetrically correct chromatic colors cannot be effectively reproduced from a technical point of view and the printing material (usually paper) is not colorimetrically neutral white .

application

Printing technology

CMYK is the standard color model of printing technology for four-color printing - but other spot colors are also specified in this model for the final printing stage . The color management within the digital print preparation takes place via ICC color profiles .

Computer technology

Inkjet printers and inkjet printers also work with CMYK colors. Many devices also have other inks: With one or more lighter shades of magenta and cyan or with shades of gray, the printer's scatter grid is less noticeable with light color mixtures. Additional inks in green, red, orange or blue expand the color range of the printer. Color laser printers and the rare color dot matrix printers also mostly work with CMYK colors.

Lighting technology

The CMYK system as well as RGB (W) can be used as a color mixing system in event technology. The different colors are generated with eleven dichroic filters. In lighting technology, lights are used directly, which means that the limited properties described for printing inks are no longer applicable; instead, black is achieved by “switching off”.

References and comments

  1. ↑ a b c d e Chris Blakley: Why is the Color Black Represented with a “K” in CMYK? In: Gearside Design. March 20, 2012, accessed February 8, 2019 .
  2. ↑ Mark Gatter: Getting it Right in Print: Digital Pre-press for Graphic Designers . Laurence King Publishing, p. 31, Four-Color Printing Explained, ISBN 978-1-85669-421-6 .
  3. ↑ Helmut S. Teschner: Color sequence . In: Offset printing technology . 10th edition, Stuttgart 1997, pp. 19/12.

literature

Web links

Commons : CMYK  - collection of images, videos and audio files