CMYK - the secret of four colors
Since 1954, Germany has had standardized color scales: DIN 16 508 for letter printing and DIN 16 509 for offset printing. Today, color printers are often the standard even in homes. But how does an RGB image get from a computer monitor to paper? And why does he need four colors? Here you can learn more about CMYK colors and how they differ from RGB and other color models.
Кak raCMYK botches?
The use of colors for display on screens and in print corresponds to the physical characteristics of the human eye. The eye is especially sensitive to three wavelengths of light. It is these colors, red, green and blue, that are used in the RGB color space. This ensures balanced color reproduction on color monitors. You can also see these colors on the LED strip, but first you need to buy an LED strip.
The printing process, on the other hand, typically prints white paper. The paper is not transparent and therefore does not transmit light. In industrial offset color printing, the four printing colors - cyan, magenta, yellow and black - CMYK - are applied to paper one after the other. The printing is not flat, but is done with very small, closely spaced dots, which the human eye perceives as a color image from a normal distance. To ensure proper image quality, industrial offset printing is often done at 300 dots per inch (dpi), which in metric terms is 11,8 print dots per millimeter. These printed dots vary in size depending on the desired thickness of ink application. If a color point is zero percent, then there is no point at that point and therefore no color.
In color printers, tiny drops of ink hit the paper in the form of printed dots, which are also located close to each other. The dot size ranges from 0,3 to 0,4 millimeters. The sum of the individual droplets in CMYK colors creates the "illusion" of a color image. A color laser printer achieves the same result, but in a different way. There are four electrically charged drums that are discharged by a laser beam at points where toner from one of the four CMYK cartridges should not reach. The remaining charged areas are then thinly coated with toner inks. These coated pixels are transferred to the paper one by one and fixed there using heat.
How many colors does the CMYK color space have?
The CMYK color space works with the primary colors cyan (blue), magenta (pink) and yellow (yellow). The letter K stands for "key" or "contrast" and represents the color black. The letter "B" was already assigned to "Blue" in the RGB color space, so it was no longer suitable for "Black". Currently, CMYK colors are standardized according to ISO 2846 - the successor to the so-called Euroscale, which was mandatory defined in DIN 16539 from 1971.
The CMYK color space is based on subtractive color mixing.
The primary colors of the CMYK color space and some approximate color mixtures according to the subtractive method can be thought of as four colors printed at different strengths on white paper. If no CMYK color is printed, the paper remains white. With RGB: All colors at "full strength" result in white.
CMYK refers to subtractive color models. Somewhat simplified, this means: if all colors are 100 percent active, the result will be black; if all colors are missing, i.e. have zero percent, (white) paper remains white. The intensity of color nuances can be compared to mixing colors from an inkbox, where, for example, blue mixed with yellow produces green, and depending on the amount of water and coloring components, different shades of green are obtained.
Important difference from RGB: The absence of all three colors (RGB = 0, 0, 0) produces black in the RGB color space. If red, green and blue have a maximum value of 255, white is produced. Thus, RGB, as an additive color model, is completely opposite to CMYK.
In practice, it has been found that printing 100% cyan, magenta and yellow produces a very dark brown tone. In the illustration above, this can be seen approximately in the color field CMYK = 90/90/90/0. This required another component to be able to print true black. Therefore, black (K) was included in the color space. At the same time, this allowed for a better appreciation of the other three colors. When using CMYK colors, it is theoretically possible to reproduce up to 4 billion different shades.
CMYK and RGB - which comes into play when?
The CMYK color model is used when physically outputting a pictorial image onto printed media - that is, onto printing machines of various technologies, as well as computer color printers using inkjet or laser technology. In the case of a four-color laser printer, this means that in addition to the black toner cartridge, three more are used containing cyan, magenta and yellow. The same applies to color inkjet printers, although other colors have been used for some time. With increasing demands on printed products, industrial printing machines have also been supplemented with additional color printing devices. In six-color printing, these are green and orange. Other multicolor printing technologies use specific spot colors, also called specialty colors.
When does the RGB color model show its strengths? Read our guide to RGB colors, which reveals the secrets of additive color mixing with RGB and also lists other color spaces.
RGB is always involved when anything is displayed on screens or monitors. Digital cameras also produce RGB image files. With RGB you can achieve 16,8 million different color shades.
What other color spaces exist?
Each print media, including each type of paper, reproduces inks with the same CMYK values slightly differently. Some absorb ink strongly, others have a smooth, glossy surface, and others have a matte surface. To be able to respond to this, standardized color profiles have been created to ensure that certain types of paper and printing inks always achieve the same print result. An example of such a color profile is the standard color profile for the printing industry in Europe "ISO Coated v2".
Color profiles also exist for scanners and monitors to match colors along the way through technical devices in a way that achieves maximum color accuracy on the output media. Data sets for standardizing color management systems are coordinated by the International Color Consortium (ICC).
Color systems go beyond this and define the composition of colors differently, and sometimes more broadly. Some of them are also based on other theoretical models of color perception by the human eye.
CIELAB
This color system is also called CIEL*a*b* or Lab colors. It is based on the human perception of the so-called normal observer - thus covering all perceived colors - and is not based on a mathematical model such as RGB or CMYK. The basic standard is EN ISO 11664-4 "Colorimetry - Part 4: CIE 1976 L*a*b* color space". Technical articles often use the term "tristimulus" for this.
H.K.S.
Currently, the HKS color system consists of 88 primary colors and 3 spot colors that can be printed on natural and fine art papers. Unlike CMYK, these colors are mixed before printing. The goal is to achieve objective comparability and reproducibility of color nuances. HKS colors can be simulated using CMYK, but their vibrancy is rarely achieved.
Pantone
Pantone Matching System is an international color system for graphics and printing developed by the American company Pantone. It contains 1 special colors (as of 867), most of which cannot be reproduced using conventional four-color printing.
RAL
Since 1927, the RAL Classics color system includes 213 color shades. Since 1993, the RAL Design System has been in existence with 1 standardized colors. Some RAL colors are corporate colors or signal colors for certain objects, for example RAL 625 as paint for fire and rescue vehicles, sea rescue cruisers and DGzRS rescue boats. The true representation of RAL colors may not be the same across monitors and printers and only approximates CMYK or RGB color specifications.
