CMYK color model

The CMYK color model is a subtractive color model, which forms the technical basis for the modern four-color printing. The abbreviation CMYK stands for the three color components cyan, magenta, yellow and black thicker Key as color depth. CMYK color spaces, as well as RGB color spaces, device-dependent and therefore require color profiles to describe colors accurately.

  • 2.1 CMY color space and CMYK color model
  • 2.2 Black Generation
  • 3.1 Printing Techniques
  • 3.2 Computer Technology

Basics

Designation

The K of CMYK refers to the key plate ( key board ) in print, the black printing plate, on which the three colored plates are aligned.

In contrast to the RGB color space, in which the order of the letters actually corresponds to the arrangement of the subpixels on most computer monitors, there is no natural order for the letters " CMYK ". Most alphabetical order for the three color components is preferred. Other spellings are common, such as the reversed alphabetical YMCK. This notation is usually the color assignments in four-color printing machines, when viewed along the paper run: White Paper, it is K, then C, then M printed, and finally Y, then the subject is completed. Although in principle all spellings are possible, as the industry standard is mostly used internationally in the graphics industry CMYK and prevents misunderstandings most likely.

ISO scale ( euro scale)

Industrial color printing with CMYK colors is called pressure on the Euro scale, because he color is based on the former European scale. This term is commonly used ( especially in the U.S. and Euro Scale) for European Offset printing. However, the Euro scale is not a correct standard, the correct term for this is ISO scale. The corresponding normalization ISO 2846 defines for ink suppliers the properties of these colors. In ISO 12647-2, the color effect of these inks is described on different printing papers. For practical application of this standard exist ICC profiles, such as " ISO Coated sb" for printing on coated papers.

Color theory

CMY color space and CMYK color model

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

In order to create true-color printing results, these have been standardized by the ISO standards 15929 and 15930. It has established itself in the European printing industry PDF/X-3 ( minimum ) standard. In North America this is something less restrictive PDF/X-1a standard. Each component ( for example, digicam, scanner, monitor, printer driver, ink, paper) must be profiled for color-accurate prints.

In the picture " CMY colors " the CMY colors are represented in 20 percent Gradierungssprüngen. The graphic is available in PDF/X-3. (Note: The magenta values ​​are added to wrong, correct, m = 0 instead of m = 1, that is, the decreasing values ​​run from top to bottom. )

It used for the CMYK color model four standard colors that Prozesscyan, process magenta, process yellow are called (even euro yellow) and process black.

Black Generation

The additional ink black (key ) for which the CMYK color model has been designed, is necessary because the tenant of the three hues not ( as the basic colors of the CMY color space for subtractive color model the behavior of light describes ) theoretically, but practically sufficient produces black. To be used in the printing of cyan, magenta and yellow pigments, there is no colorant which has the required optical properties of an optimal color. On the other hand, black is absolutely necessary for the achromatic an image. It is determined for the separation of the image, in order to avoid that too many colors to be printed over each other. Prevent the real absorption properties of pigments for printing inks, that a mixture of three primary colors actually produces black, so a uniform extinction of the intensities. The result is a dark brown. In practice, one takes the pigment is carbon black, which is usually fined with reflex blue to cover the natural red tint for a pure deep black. Also, to improve the contrast in dark image or drawing parts black is used in four-color printing. In addition, the colorimetric correct chromatic colors can not technically effectively adjust, and the substrate (usually paper ) is not colorimetrically neutral white.

Application

Printing Techniques

CMYK is the standard color model of printing technology for four-color printing - but also more spot colors are given in this model for the pressure amplifier. The color management within the digital prepress via ICC color profiles.

Computer Technology

Even inkjet printers and inkjet printers usually work with CMYK colors. Many devices have, however, plus an additional inks: One or more lighter shades of magenta and cyan, or even shades of gray, the scattering pattern of the printer will be less visible in bright color mixtures. Additional inks in green, red, orange and / or blue expand the color gamut of the printer. Even color laser printer and the rare paint needle printers usually work with CMYK colors.

Several manufacturers also offer CMYKT Printer. The "T " stands for top coat, a special paint for coating the paper with a particularly light-resistant, glossy or waterproof protective layer.

Substrate (printing) Dot matrix printer IBM
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