CMYK Definition and Meaning

CMYK color model. The CMYK model (acronym for Cyan, Magenta, Yellow and Key according to AbbreviationFinder) is a subtractive Color model used in Color Printing.


This 32-bit model is based on mixing pigments of the following colors to create more:

* C = Cyan (Cyan). * M = Magenta (Magenta). * Y = Yellow (Yellow). * K = Black or Key (Black).

Ideal CMY color mixing is subtractive (printing cyan, magenta, and yellow on a white background results in black). The CMYK model is based on the absorption of light. The color that an object presents corresponds to the part of the Light that falls on it and that is not absorbed by the object.

Cyan is the opposite of red, which means that it acts as a filter that absorbs that color (-R + G + B). Magenta is the opposite of green (+ R -G + B) and yellow is the opposite of blue (+ R + G -B).

Using black ink

For various reasons, the black generated by mixing the Subtractive Primary Colors is not ideal and therefore four-ink printing uses black in addition to the subtractive primary colors yellow, magenta, and cyan. These reasons include:

  • A mixture of yellow, cyan, and magenta pigments rarely produces pure black because it is almost impossible to create sufficient amounts of pure pigments.
  • Mixing the three inks just to form black can make the paper wet if a dry toner is not used, which is a problem in fast printing where the paper must dry fast enough to avoid marking the next sheet. Also, poor quality paper, such as that used for newspapers, can tear if it gets too wet.
  • Text is often printed in black and includes fine details if the typeface is Serif. To reproduce the text using three inks without the typographic symbol fading or fading slightly, extremely accurate registration would be required. This way of generating the black color is not possible, in practice, if a faithful reproduction in the density and contour of the typography is desired (by having to align the three images with too much precision).
  • From an economic point of view, the use of one unit of black ink, instead of three units of color inks, can mean a great saving, especially since black ink is generally much cheaper than any ink of colour.

Black is called a key, instead of using the letter B, as it is a short name of the term key plate used in printing. This master plate printed the artistic detail of an image, usually in black ink. The use of the letter K also helped avoid confusion with the letter B used in the acronym RGB. The amount of black to use, to replace the amounts of the other inks, is variable and the choice depends on the technology, the type of paper and the kind of ink used. Processes such as under color removalunder color addition and gray component replacement are used to decide the final mix, whereby different CMYK recipes will be used depending on the print job. When black is mixed with other colors, it results in a blacker black called “rich black”, or “registration black”.

Comparison with RGB model

Using four-ink printing produces a good result with higher contrast. However, the color seen on a computer monitor is often different from the color of the same object in a print, since the CMYK and RGB models have different color gamuts. For example, Pure Blue (In 24 and 32 bit RGB 0,0,255) is impossible to reproduce in CMYK. The closest equivalent in CMYK is a blue-purple hue.

The monitors of computer, and other screens, use the RGB model, representing the color of an object as an additive mixture of light red, greenand blue (whose sum is white light). In printed materials, this combination of light cannot be directly reproduced, so the images generated in computers, when using an editing program , Vector Drawing, or Photo Retouching must be converted to its equivalent in the CMYK model that It is suitable when using a device that uses inks, such as a Printer, or an offset machine.

RGB to CMYK mapping

A given RGB color can be mapped to one of many possible semi-equivalent CMYK colors. The best option is one that uses K as much as possible, and remaining CMY ratios as little as possible. For example, # 808080 (gray, the exact half between black and white) will be mapped to (0,0,0,0.5) and not to (0.5,0.5,0.5,0).

Its use in graphic arts

Its widespread use occurs in the context of graphic arts. The offsets printers print generally in 4 colors more special inks flat, if the case arises (those commonly called color Pantone). This is why, before sending any work to the printing press, we must convert the colors of the document to CMYK so that the printing colors are as correct as possible.