CMYK color model

When CMY colors are combined at full strength, the resulting pair mixtures are red, green, and blue. Mixing all three gives very dark grey.

The CMYK color model is a subtractive color model, based on the CMY color model, used in color printing. CMYK refers to the four inks used in printing: cyan, magenta, yellow, and key (black).

The CMYK model is subtractive. It means that it subtracts or masks colors from white background of the paper. The ink reduces the reflected light. White light minus red leaves cyan, white light minus green leaves magenta, and white light minus blue leaves yellow.

White is the natural color of the paper, while black results from a full combination of colored inks. To save cost on ink, and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of pure mix of cyan, magenta, and yellow.

Using black ink

A sample of four-color printing process.

The "black" produced by mixing usual cyan, magenta, and yellow inks is actually a dark grey color. So, modern four-color printing uses black ink in addition to the subtractive primary colors. Common reasons for using black ink include:

• Text is typically printed in black and includes fine detail, difficult to reproduce with a mix of three inks.
• A combination of 100% cyan, magenta, and yellow inks soaks the paper with ink, making it slower to dry.
• Although a combination of 100% cyan, magenta, and yellow inks should, in theory, produce a perfect black, practical inks cannot do it and the result is actually a dark muddy color that does not quite appear black.
• Using black ink is less expensive than using the corresponding amounts of colored inks.

CMYK Color Model Media

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  This diagram shows three examples of color halftoning with CMYK separations, as well as the combined halftone pattern and how the human eye would observe the combined halftone pattern from a sufficient distance.

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  A color photograph of the Teton Range.

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  Inspection CMYK colors of offset printing on a paper

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  Comparison of some RGB and CMYK color gamut on a CIE 1931 xy chromaticity diagram.

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  Spectrum of the visible wavelengths on printed paper (SCA Graphosilk). Shown is the transition from red to yellow. White, red, blue, and green are shown for reference. Readings from a white orchid flower, a rose (red and yellow petals), and a red cyclamen flower are shown for comparison. The units of spectral power are simply raw sensor values (with a linear response at specific wavelengths).

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  Early representation of the three-color process (1902)

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  Approximation of the image using CMY colors.

Related pages

• CMY color model
• RGB color model
• Color model

Other websites

• XCmyk Archived 2011-12-30 at the Wayback Machine – CMYK to RGB Calculator with source code
• Color Space Fundamentals – animated illustration of RGB vs. CMYK