What is CMYK?

According to AbbreviationFinder.org, the CMYK model (acronym for Cyan, Magenta, Yellow and Key) 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.

Differences between RGB and CMYK colors when working with Photoshop

When starting to work on a project with Photoshop, it is essential to decide which mode or type of color to use. RGB and CMYK modes can be indifferent to the naked eye, but choosing one or the other can help or create problems. What are the differences between them according to their use and color theory?

RGB, colors by adding light

The RGB color model is an acronym for the three basic colors that make it up: red, green and blue or what is the same, in English, red, green and blue. This model uses the mixture of these three basic colors to create a pixel of a certain color.

Each of the three colors has an intensity ranging from zero to 255, thus creating 256 different shades for that color. The combination of these three variants offers a palette of more than 16 million colors.

When dealing with light colors, the sum of the three to the maximum of their hue will result in the color white, while the sum of the three colors at their zero value will create the color black.

Using an RGB color mode

In graphic design, work will be done in RGB mode as long as the final result of the work is intended for a screen support. This means that this mode will be chosen if you are working for the web, for an online presentation or for video. GIF and JPG files will be the most used when working in this mode.

If you look at a screen with a magnifying glass, you can distinguish the pixels that make it up, and in each of them a subdivision with the three basic colors of RGB: red, green and blue.

CMYK colors, by adding ink

CMYK colors are those that are created from the sum of four inks of different colors: cyan, magenta, yellow, and black. In English, the acronyms come from cyan, magenta, yellow and black.

Unlike in CMYK mode, these values ​​will be darker the higher their percentage. In addition, these colors have, in Photoshop, a range that goes from zero to one hundred (instead of the 256 levels of RGB).

In pure theory, it would be enough to add cyan, magenta and yellow to obtain the color black, but the reality of the printing shows that the mixture of these three colors to the maximum of their tonality gives a dark brown color. For this reason, to work in graphic design, a fourth color is added, black.

Using CMYK color mode

The CMYK color mode is used whenever your work is designed for print output. It should be noted that the result of a printed job will never be the same, in terms of colors, as what the user sees on the screen. However, working in CMYK mode there will be fewer surprises when the design is printed.

Change color mode in Photoshop

The color mode of a Photoshop file can be changed from the ‘image> mode’ menu.

Sometimes it will happen that you start working in RGB mode and then change the color mode to CMYK. This change usually involves an alteration in the colors of the design, which becomes duller when it is switched to ink colors. The difference will be more appreciated in the areas with more vivid, more luminous colors, and will be especially accentuated if they belong to the range of green or blue.


It is interesting to note that the conversions mentioned here are of the nominal type. They will produce an irreversible conversion between RGB and a subset of CMYK; that is, you can choose a color from the RGB palette and convert it to certain CMYK colors, and from these CMYK colors obtain the original RGB equivalents that correspond to them. However, converting from CMYK to RGB colors is generally not reversible; that is, a color given in CMYK and converted to RGB will not result in the original CMYK color when it is reconverted back to the CMYK palette.

In addition, CMYK colors can be printed in very different tones than they are seen on a monitor. There is no “good” conversion rule between RGB and CMYK, because neither model represents an absolute color space.

Converting between RGB and CMYK

To convert between RGB and CMYK, an intermediate CMY value is used. The color values ​​are represented as a vector, each of which can vary between 0.0 (non-existent color) and 1.0 (fully saturated color).

CMYK to RGB conversion

To achieve the conversion, you first go from CMYK to CMY, and then to RGB.

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.