color models

Description of the known color systems or models used in design, computing and electronics: RGB, CMYK, HSV, Pantone.

The colors obtained directly naturally by decomposition of sunlight or artificially by emitting light bulbs of a given wavelength are called additive colors.

The union of all the lengths of the visible spectrum is not necessary to obtain white, since if we mix only red, green and blue we will obtain the same result. This is why these colors are called primary colors, because the sum of the three produces white. In addition, all the colors of the spectrum can be obtained from them.

Additive colors are those used in graphic work with computer monitors, since, as we saw when we talked about the graphic components of a computer, the monitor produces points of light from three cathode ray tubes, one red, one green, and one red. another blue. For this reason, the color definition model used in digital works is the RGB model (Red, Green, Blue).

All colors displayed on the monitor are based on the amounts of red, green and blue used. Therefore, to represent a color in the RGB system, it is assigned a value between 0 and 255 (decimal notation) or between 00 and FF (hexadecimal notation) for each of the red, green and blue components that make it up. Higher RGB values ​​correspond to a greater amount of white light. Therefore, the higher the RGB values, the lighter the colors.

In this way, any color will be represented in the RGB system by means of the decimal syntax (R,G,B) or by means of the hexadecimal syntax #RRGGBB. The pure red color, for example, will be specified as (255,0,0) in decimal RGB notation and #FF0000 in hexadecimal RGB notation, while the light pink color given in decimal notation by (252,165,253) corresponds to the hexadecimal color #FCA5FD.

This additive way of perceiving color is not unique. When sunlight strikes the surface of an object, it absorbs different wavelengths of its full spectrum, while reflecting others. These reflected wavelengths are precisely the cause of the colors of the objects, colors that, because they are produced by filtering wavelengths, are called subtractive colors.

This phenomenon is what occurs in painting, where the final color of an area will depend on the wavelengths of the incident light reflected by the color pigments in it.

A car is blue because it absorbs all the wavelengths that make up sunlight, except for the one corresponding to the color blue, which it reflects, while an object is white because it reflects the entire spectrum of waves that make up light, that is, it reflects all colors, and the result of mixing all of them results in white. For its part, an object is black because it absorbs all the wavelengths of the spectrum: black is the absence of light and color.

In this subtractive conception, the primary colors are others, specifically cyan, magenta and yellow. From these three colors we can obtain almost all the others, except white and black.

Indeed, the mixture of cyan, magenta and yellow pigments does not produce the color white, but a dirty, neutral gray color. As for black, it is not possible to obtain it from the primaries either, being necessary to include it in the set of subtractive basic colors, obtaining the CMYK model (Cyan, Magenta, Yellow, Black).

The CMYK system defines colors in a similar way to how an inkjet printer or a commercial four-color printer works. Color results from superimposing or placing drops of semi-transparent ink together, in the colors cyan (a bright blue), magenta (a deep pink), yellow, and black, and its notation corresponds to the value in percent of each of these colors.

In this way, any color will be expressed in the CMYK system by means of the expression (C,M,Y,K), which contains the percentages that the color has of the basic components of the system. For example, (0,0,0,0) is pure white (the white of the paper), while (100,0,100,0) corresponds to the color green.

Subtractive colors are used in painting, printing and, in general, in all those compositions in which the colors are obtained by the reflection of sunlight in mixtures of pigments (inks, oils, watercolors, etc.). In these compositions, the white color is obtained by using pigments of that color (paint) or by using a white support and leaving the areas of the composition that should be white unpainted (printing).

The RGB, CMYK systems are related, since the primary colors of one are the secondary colors of the other (secondary colors are those obtained by direct mixing of the primaries).

Another color definition model is the HSV model, which defines colors based on the values ​​of three important color attributes, hue, saturation, and brightness.

The hue (Hue) refers to the color as such, for example the hue of blood is red. Saturation or intensity indicates the concentration of color in the object. The red saturation of a strawberry is greater than that of the red of lips. On the other hand, the brightness (Value) denotes the amount of clarity that the color has (more or less dark hue). When we talk about brightness, we refer to the process by which white is added or subtracted from a color. We will study these concepts in detail later.

Finally, there are different commercial color definition systems, the best known of which is the Pantone system.

Created in 1963 and looking for a standard for the communication and reproduction of colors in the graphic arts, its full name is Pantone Matching System, and it is based on the publication of a series of catalogs on various substrates (surfaces to be printed), which provide a standardized coding through a reference number and a specific color.

In the following article we will expand this information by doing a study on the etc.