About color spaces. Color models and their types

The science of color is a rather complex and large-scale science, in this regard, various color models are created in it from time to time, which are used in a particular area. One of these models is color circle.

Many people know that there are 3 primary colors͵ which cannot be obtained and which form all the others. Primary colors- ϶ᴛᴏ yellow, red and blue. At

mixing yellow with red turns out orange, blue and yellow are green, and red and blue are purple. Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, you can make a circle that contains all the colors. It is shown in Fig. and it is customary to call Oswald's great circle.

Along with Oswald's circle, there is also goethe circle, in which the primary colors are located at the corners of an equilateral triangle, and the complementary colors are located at the corners of an inverted triangle.

Contrasting colors are located opposite each other.

Different mathematical models are used to describe the emitted and reflected color - color models ( color space), ᴛ.ᴇ. - ϶ᴛᴏ a way of describing color using quantitative characteristics. Color models are hardware-dependent(they are still the majority, RGB and CMYK among them) and hardware independent(Lab model). In most "modern" rendering packages (for example, in Photoshop), you can convert an image from one color model to another.

In the color model (space), each color can be assigned a strictly defined point. In this case, the color model is simply a simplified geometric representation based on a coordinate system and an assumed scale.

Basic color models:

- CMY (Cyan Magenta Yellow);

- CMYK (Cyan Magenta Yellow Key, where Key means black);

- HSV (Hue, Saturation, Value);

- HLS (Hue, Lightness, Saturation);

- and others.

In digital technologies, at least four basic models are used: RGB, CMYK, HSB in various versions and Lab. Numerous spot color libraries are also used in the printing industry.

The colors of one model are complementary to the colors of the other model. Complementary color- a color complementary to the given one to white. Additional for red - cyan (green + blue), additional for green - magenta (red + blue), additional for blue - yellow (red + green-green), etc.

According to the principle of operation, the listed color models can be conditionally divided into three classes:

- additive (RGB), based on the addition of colors;

- subtractive (CMY, CMYK), which are based on the operation of subtractive colors (subtractive synthesis);

- perceptual (HSB, HLS, LAB, YCC) based on perception.

Additive color is obtained on the basis of Grassmann's laws by combining rays of light of different colors. At the root of this phenomenon lies the fact that most of the colors in the visible spectrum are obtained by mixing in various proportions of the three basic color components. These components, which in color theory are sometimes called primary colors are red ( R ed), green-green ( G reen) and blue ( V lue) colors. When mixed in pairs, the primary colors are formed secondary colors: blue ( WITH yan), magenta ( M agenta) and yellow ( Y ellow). It should be noted that primary and secondary colors refer to basic flowers.

Basic colors are called colors͵ with which you can get almost the entire spectrum of visible colors.

To obtain new colors using additive synthesis, you can use various combinations of two basic colors, varying the composition of which leads to a change in the resulting color.

Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, color models (color space) represent a means for conceptually and quantitatively describing color. Color mode - ϶ᴛᴏ a way to implement a specific color model within a specific graphics program.

Grassmann's law (color mixing laws)

Most color models use a three-dimensional coordinate system to describe color. It forms a color space in which a color can be represented as a point with three coordinates. To operate with color in three-dimensional space, T. Grassman derived three laws (1853):

1. Color is three-dimensional - three components are needed to describe it. Any four colors are linearly dependent, although there is an unlimited number of linearly independent collections of three colors.

In other words, for any given color, you can write down such a color equation that expresses the linear dependence of colors.

The first law can be interpreted in a broader sense, namely, in the sense of three-dimensionality of color. It is not necessary to use a mixture of other colors to describe a color, you can use other values ​​- but there must be three of them.

2. If in a mixture of three color components one changes continuously, while the other two remain constant, the color of the mixture also changes continuously.

3. The color of the mixture depends only on the colors of the components being mixed and does not depend on their spectral compositions.

The meaning of the third law becomes clearer if we take into account that the same color (including the color of the mixed components) must be obtained in different ways. For example, a miscible component must in turn be obtained by mixing other components.

RGB color model

This is one of the most common and frequently used models. It is used in devices that emit light, such as monitors, spotlights, filters and other similar devices.

This color model is based on three basic colors: Red - red, Green - green and Blue - blue. Each of the above components can vary from 0 to 255, producing different colors and thus providing access to all 16 million (the total number of colors represented by this model is 256 * 256 * 256 = 16 777 216.).

This model additive. The word additive (addition) emphasizes that the color is obtained by adding the points of three basic colors, each with its own brightness. The brightness of each base color can take values ​​from 0 to 255 (256 values), so the model can encode 256 3 or about 16.7 million colors. These triplets of base points (luminous points) are located very close to each other, so that each triplet merges for us into a large point of a certain color. The brighter the color point (red, green, blue), the more of this color will be added to the resulting (triple) point.

When working with the graphics editor Adobe PhotoShop, you can choose a color, relying not only on what we see, but if it is extremely important to indicate a digital value, thereby sometimes, especially in color correction, controlling the work process.

Good day to you, dear readers of my blog. I am very glad to see you on the pages of my blog. Today I would like to go over the theory a little, namely to talk about color models in computer graphics. Do not be afraid, there is nothing terrible here, but you need to know this, as soon it will be useful to us. I will not tell you the scientific definition of a color model, as it is too clever.

The choice of color model depends mainly on what we need this or that image for, for what purposes. Okay, I won't torture you. Let's take a look at several color models that you will come across in various graphic editors.

In this mode, only 2 colors are available to us, namely black and white. So what have we forgotten here? Right! Nothing. Therefore, I say right away - we will not use this mode.

Grayscale

As the name suggests, this mode uses only shades of gray. There are 256 such shades of gray in total. there is a constant increase in brightness, starting with black, and until it becomes completely white. Of course, if you want to work with a black and white image, then please, because this image will take up much less space. But, I'll tell you a secret, we will not use this mode either. You are happy?

RGB (Red Green Blue)

Well, now we have moved on to the basic color model. It is she who we will mainly use in Photoshop. This model is used to display colors on the screen. All colors and shades are obtained by mixing the three primary colors, i.e. red ( R ed), green ( G reen) and blue ( B lue). You ask: “Where is yellow? After all, it cannot be obtained by mixing these colors. " Just the same it turns out, but not on paper, but on the monitor screen. We can get yellow by mixing red and green. Here's a trick.

There are a lot of colors in this model! There are 16 million of them in 8-bit representation! Can you imagine how many there will be in 16 and 32 bits? Therefore, I immediately conjure you - choose only the 8-bit RGB representation, since there is no point in the rest, at least in ordinary life. We will assume that we have agreed.

CMYK (Cyan Magenta Yellow Black)

This color model is derived from the letters of the four colors. C yan M agenta Y ellow K ey color - Cyan, Magenta, Yellow, Key-black. Although I read in some sources that the letter K formed not from the Key color, but from the black color black, only they decided not to assign a letter to it B, since it was already used in the RGB color model as blue, so they gave it the last letter from the word blac K... But this does not change the essence.

This model is usually used in printing and preparation for printing, that is, for display on paper. Again, I'll say right away that in our lessons we will practically not use it. But we'll look at it. Just want to tell you why this model uses 4 colors along with black? Because if you mix all the colors in the RGB model, you get black, and if you mix all the colors in the CMY model, then black will not work, the maximum is dark brown. In addition, complete mixing of all colors can deform the paper. Therefore, we added the key black color K.

LAB

Well, since we're talking about color models, I can't help but tell you about such a thing as LAB. This model consists of three parameters:

1. L uminance - illumination. The gradation goes from light to dark.
2. Colour A- gamut of colors from green to purple
3. Colour B- a range of colors from blue to yellow.

As you can see, the first letters of the parameters make up this abbreviation. That is, this model involves mixing two colors with a certain degree of illumination. What is remarkable about this model is that it contains both RGB and CMYK colors, and even grayscale, which we talked about above.

And if the RGB model displays colors as we see it on the screen, and CMYK as on paper, then the LAB model corresponds to human vision, i.e. as an ordinary person sees it.

HSB or HSV

And finally, let's catch one more model that you may meet. This model consists of three parameters: Hue, Saturation and Brightness / Value of the color. This model is based on the previously considered RGB, but unlike RGB (16 million colors), HSB can contain only about 2.5 million colors.

Often such a model is depicted as a color wheel and an additional vertical bar of brightness. Maybe you met somewhere? But besides this, different programs may have different representations.

In general, this concludes my review of color models. I'll tell you right away that when we go through Photoshop, we will mainly use the RGB model. And by the way, I did not give you this information in vain, since soon we will really move on to studying the graphics editor Adobe Photoshop. So don't relax.

And this is where our theoretical lesson is over. I hope that everything was more or less clear to you. In which case, you can always ask a question in the comments or in the feedback form. And do not forget to subscribe to the updates of the articles of my blog and then you will always be aware of everything interesting from the very first! Good luck, get ready for new lessons. Bye Bye!

Color and its models

Sofya Skrylina, teacher of the training center "Art", St. Petersburg

In ComputerArt No. 7 "2012, an article was presented about harmonious color combinations and patterns of influence of color on human perception, which, undoubtedly, modern designers take into account in their projects. But when working at a computer and mixing colors on a monitor screen, specific problems arise. A designer should get on a monitor screen or hard copy exactly the color, tone, tint and lightness required.Colors on the monitor do not always match natural colors.It is very difficult to get the same color on the screen, on a printout of a color printer and on a typographic print. The fact is that colors in nature, on a monitor and on a printed sheet, are created in completely different ways.
For the unambiguous definition of colors in different color environments, there are color models, which we will talk about in this article.

RGB model

The RGB color model is the most popular way to represent graphics and is suitable for describing the colors visible on a monitor, TV, video projector, as well as images created by scanning.

The RGB model is used to describe colors produced by mixing three rays: Red, Green, and Blue. The name of the model is made from the first letters of the English names of these colors. The rest of the colors are obtained by combining the base colors. Colors of this type are called additive, because when two rays of primary colors are added (mixed), the result becomes lighter. In fig. 1 shows what colors are obtained when adding the main ones.

In the RGB model, each base color is characterized by a brightness that can take 256 values ​​- from 0 to 255. Therefore, you can mix colors in different proportions, changing the brightness of each component. Thus, you can get 256x256x256 = 16,777,216 colors.

Each color can be associated with a code using decimal and hexadecimal code representations. Decimal notation is a triple of decimal numbers separated by commas. The first number corresponds to the brightness of the red component, the second to the green, and the third to the blue. Hexadecimal representation is three two-digit hexadecimal numbers, each representing the luminance of the base color. The first number (first pair of numbers) corresponds to the brightness of red, the second number (second pair of numbers) to green, and the third (third pair) to blue.

To verify this fact, open the color picker in CorelDRAW or Photoshop. In the R box, enter 255 for the maximum luminance for red, and zero in the G and B boxes. As a result, the sample field will contain red, the hexadecimal code will be: FF0000 (Fig. 2).

Rice. 2. Representation of red in the RGB model: on the left - in the Photoshop palette window, on the right - CorelDRAW

If you add green with maximum brightness to red by entering 255 in the G field, you get yellow, the hexadecimal representation of which is FFFF00.

The maximum brightness of all three basic components corresponds to white, the minimum to black. Therefore, white has the code (255, 255, 255) in decimal notation, and FFFFFF16 in hexadecimal. Black is coded accordingly (0, 0, 0) or 00000016.

All shades of gray are formed by mixing three components of the same brightness. For example, R = 200, G = 200, B = 200, or C8C8C816 produces a light gray, while R = 100, G = 100, B = 100, or 64646416 produces dark gray. The darker the shade of gray you want, the lower the number you need to enter in each text box.

What happens when an image is printed, how are colors rendered? After all, paper does not emit, but absorbs or reflects color waves! When transferring a color image to paper, a completely different color model is used.

CMYK Model

When printing, ink is applied to paper - a material that absorbs and reflects color waves of various lengths. Thus, the paint acts as a filter that allows certain rays of the reflected color to pass through, subtracting all the others.

The CMYK color model is used for mixing inks by printing devices - printers and printing presses. The colors of this model are obtained by subtracting the base colors of the RGB model from white. Therefore, they are called subtractive.

The following colors are basic for CMYK:

• blue (Cyan) - white minus red (Red);
• magenta - white minus green (Green);
• yellow - white minus blue (Blue).

In addition to these, black is also used, which is the key (Key) in the process of color printing. The fact is that real paints have impurities, so their color does not correspond exactly to the theoretically calculated cyan, magenta and yellow. Mixing the three base paints, which should be black, produces a vague mud brown instead. Therefore, black is included in the number of basic printing inks.

In fig. 3 is a diagram showing what colors are obtained by mixing the base in CMYK.

It should be noted that CMYK colors are not as pure as RGB colors. This explains the slight discrepancy between the base colors. According to the diagram shown in Fig. 3, at maximum brightness, the following color combinations should be obtained:

• mixing magenta (M) and yellow (Y) should give red (R) (255, 0, 0);
• mixing yellow (Y) and blue (C) should give green (G) (0, 255, 0);
• mixing magenta (M) and cyan (C) should produce blue (B) (0, 0, 255).

In practice, it turns out a little differently, which we will check later. Open the color picker dialog box in Photoshop. Enter 100% in the M and Y text boxes. Instead of the base red color (255, 0, 0), we have a red-orange mixture (Fig. 4).

Now enter 100% in the Y and C text boxes. Instead of the base green (0, 255, 0), the result is green with a slight tint of blue. When setting the brightness to 100% in the M and C fields, instead of blue (0, 0, 255), we have a blue color with a purple tint. Moreover, not all RGB colors can be represented in CMYK. RGB color gamut is wider than CMYK.

The primary colors of the RGB and CMYK models are in the dependence shown on the color wheel scheme (Fig. 5). This scheme is used for color correction of images; examples of its use were considered in ComputerArt No. 12 "2011.

RGB and CMYK models are hardware dependent. For RGB, the base color values ​​are determined by the quality of the phosphor on a CRT or by the characteristics of the backlight and panel color filters on LCD monitors. If we turn to the CMYK model, then the values ​​of the base colors are determined by the actual printing inks, the peculiarities of the printing process and the media. Thus, the same image may look different on different equipment.

As noted earlier, RGB is the most popular and commonly used model for representing color images. In most cases, images are prepared for display via a monitor or projector and for printing on color desktop printers. In all these cases, the RGB model must be used.

Comment

Although color printers use CMYK ink, most often images that are prepared for printing need to be converted to RGB. However, the printed image will appear slightly darker than on the monitor, so it must be lightened before printing. The amount of lightness for each printer is determined empirically.

The CMYK model must be used in one case - if the image is being prepared for printing on a printing press. Moreover, it should be borne in mind that the CMYK model does not contain as many colors as the RGB model, therefore, as a result of converting from RGB to CMYK, the image may lose a number of shades that are unlikely to be restored by reverse conversion. Therefore, try to carry out the conversion of the image to CMYK model at the end of the work with it.

HSB model

The HSB model simplifies the work with colors, as it is based on the principle of color perception by the human eye. Any color is determined by its Hue - the color itself, Saturation - the percentage of adding white paint to the color and Brightness - the percentage of adding black paint. In fig. 6 shows a graphical representation of the HSB model.

Spectral colors, or color tones, are located at the edge of the color wheel and are characterized by a position on it, which is determined by an angle in the range from 0 to 360 °. These colors have maximum (100%) saturation (S) and brightness (B). Saturation changes along the radius of the circle from 0 (in the center) to 100% (at the edges). At 0% saturation, any color becomes white.

Brightness is a parameter that determines lightness or darkness. All colors in the color wheel are at their maximum brightness (100%) regardless of hue. Decreasing the brightness of a color means darkening it. To display this process, a new coordinate directed downward is added to the model, on which the brightness values ​​from 100 to 0% are plotted. The result is a cylinder formed from a series of circles of decreasing brightness, the bottom layer being black.

To verify this statement, open the color picker dialog box in Photoshop. In the S and B fields, enter a maximum value of 100%, and in the H field, enter a minimum value of 0 °. As a result, we get the pure red color of the solar spectrum. The same color corresponds to the red color of the RGB model, its code (255, 0, 0), which indicates the relationship between these models (Fig. 7).

In the H field, change the angle value in 20 ° increments. You will receive the colors in the order in which they are located in the spectrum: red will change to orange, orange to yellow, yellow to green, etc. An angle of 60 ° gives yellow (255, 255, 0), 120 ° - green (0, 255, 0), 180 ° - blue (255, 0, 255), 240 ° - blue (0, 0, 255), etc.

To get a pink color, in the language of the HSB model - a faded red, you must enter a value of 0 ° in the H field, and lower the saturation (S), for example, to 50%, setting the maximum brightness value (B).

Gray for the HSB model is zeroed hue (H) and saturation (S) with luminance (B) less than 100%. Here are examples of light gray: H = 0, S = 0, B = 80% and dark gray: H = 0, S = 0, B = 40%.

White color is set as follows: H = 0, S = 0, B = 100%, and to get black color, it is enough to reduce the brightness value to zero at any values ​​of hue and saturation.

In the HSB model, any color is obtained from the spectral color by adding a certain percentage of white and black dyes. Therefore, HSB is a very easy-to-understand model used by painters and professional artists. They usually have several base colors, and all others are obtained by adding black or white to them. However, when artists mix paints based on base paints, the color goes beyond the HSB model.

Lab model

The Lab model is based on the following three parameters: L- brightness (Lightness) and two chromatic components - a and b... Parameter a changes from dark green through gray to magenta. Parameter b contains colors from blue through gray to yellow (Fig. 8). Both components change from -128 to 127, and the parameter L- from 0 to 100. Zero value of color components at brightness 50 corresponds to gray color. A luminance value of 100 produces white, and 0 produces black.

The concepts of brightness in the Lab and HSB models are not the same. As in RGB, mixing colors from scales a and b produces brighter colors. You can reduce the brightness of the resulting color using the parameter L.

Open the color picker in Photoshop, in the brightness field L enter value 50, for parameter a enter the smallest value -128 and the parameter b reset to zero. As a result, you will get a blue-green color (Fig. 9). Now try increasing the parameter value a per unit. Please note that the numeric values ​​have not changed in any model. Try increasing the value of this parameter to achieve changes in other models. You will most likely be able to do this with a value of 121 (the green component of RGB will decrease by 1). This circumstance confirms the fact that the Lab model has b O Greater color gamut than RGB, HSB and CMYK models.

In the Lab model, the brightness is completely separated from the image, so in some cases this model is convenient to use for recoloring fragments and increasing the saturation of the image, affecting only the color components a and b... It is also possible to adjust the contrast, sharpness and other tonal characteristics of the image by changing the brightness parameter L... Examples of image correction in the Lab model were given in ComputerArt No. 3 "2012.

The Lab model has a wider color gamut than RGB, so every re-conversion from one model to another is practically safe. Moreover, you can put the image in Lab mode, perform corrections in it, and then painlessly convert the result back to RGB.

The Lab model is hardware independent, serves as the core of the color management system in the graphics editor Photoshop, and is applied in a hidden form at each color model conversion as an intermediate one. Its color range covers both RGB and CMYK ranges.

Indexed colors

To publish an image on the Internet, not the entire color gamut, consisting of 16 million colors, as in RGB mode, is used, but only 256 colors. This mode is called Indexed Color. A number of restrictions are imposed on the work with such images. Filters cannot be applied to them, some commands for tone and color correction, all operations with layers are not available.

With an image downloaded from the Internet (usually in GIF format), the following situation often arises. You can draw something in it only with a color different from the selected one. This is because the selected color is outside the color palette of the indexed image, that is, this color is not in the file. As a result, the color selected in the palette is replaced with the closest similar color from the color table. Therefore, before editing such an image, it is necessary to convert it to the RGB model.

The article was prepared on the basis of the book by Sofya Skrylina “Photoshop CS6. Most Necessary ": http://www.bhv.ru/books/book.php?id=190413.

All graphics programs in the form of color selection have switches for color models. This is usually a dropdown list with options for CMYK, RGB, LAB, HSB, HLS, and Grayscale. It seems to be the same colors, only in different measurement systems. Why offer a choice at all?

If you asked yourself such a question, then this article will be useful to you.

What is a color model?

A color model is a mathematical model for describing colors as a set of numbers called color components or color coordinates. All possible color values ​​given by the model define the color space.

Why do you need to know about color models?

The color that you see on the monitor when developing the layout and the color that is obtained when printing on paper are generated in completely different ways. Each of these color reproduction methods uses a different color model, and each model has a different color gamut.

If you have created an RGB color in a graphics program, it is likely that it cannot be printed on paper. Perhaps the color gamut of printing (CMYK model) simply does not contain such a color, and in the printed product you will get something completely different from what you asked in the layout.

Today we will look at 3 main color separation models: RGB, CMYK and Lab.

RGB is an abbreviation of the first letters of the names of the primary colors that make up the shades in this model: red, green, and blue.

Color is created by combining these three primary colors and the entire spectrum of shades of this model can be observed only with the emitted light (that is, on a TV, computer or telephone screen). Each pixel of the screen burns with its own color due to the addition of these primary colors in certain proportions.

Cyan (cyan), magenta (magenta), yellow (yellow) and black (black. In the abbreviation denoted by the letter K, which stands for Key color).

If rgb describes the colors that are emitted, then cmyk describes the reflected colors. When the light hits the print and you see the color, it's cmyk. The entire spectrum that can be obtained with cmyk colors is much less than rgb, and therefore, when creating a layout for printing, it is strongly recommended to use this particular model in graphic programs.

In offset printing, these four inks are placed in separate sections of the printing press. Each section has its own printing plate, which is responsible for applying the appropriate paint to the sheet of paper where it is needed.

When a white sheet enters the printing machine, it flies through all four sections, in each of which one of the primary colors is printed on the sheet, and a print with a full-color image flies out of the machine.

Unlike the first two models, here the letters do not represent the primary colors. L is lightness, a and b are abstract coordinates.

LAB has no gamut limitations. It even describes colors that neither the printing press, nor the printer, nor the monitor can reproduce.

The cryptic RGB and CMYK are both basic graphic design knowledge. We'll talk about color rendering differences so that it becomes clear why the same color in a layout on a computer screen and on paper will look different. Perhaps you have already encountered something similar when ordering printing.

A color model is a way of describing color in terms of quantitative characteristics. A color model is usually understood as a term that refers to an abstract model for describing the representation of colors in the form of three- or four-digit numbers called color components (sometimes color coordinates). The color model is used to describe the emitted and reflected colors. Together with the method of interpreting this data, the set of colors of the color model determines the color space.

What is RGB

Let's start with the numbers. 16.7 million shades are displayed on a modern computer monitor or a good printing device. Such a large palette is obtained by mixing only three colors in different proportions - red, blue and green. In graphic editors, each of them is represented by 256 shades (256x256x256 = 16.7 million).

RGB- the color model, named after the three capital letters of the color names that underlie it: Red, Green, Blue, or red, green, blue. All intermediate colors form the same colors. The scientific name is additive model (from the English word add - "to add"). Serves for displaying images on screens of monitors and other electronic devices. Has a large color gamut.

The RGB color model assumes that the entire palette is made up of points of light. This means that it is impossible to depict color in the RGB color model on paper, since the paper absorbs color, and does not glow. The original color can be obtained by adding a percentage of each of the key colors to the non-luminous - or initially black - surface.

An RGB color is obtained by mixing red, blue and green in different proportions: each hue can be described by three numbers, denoting the brightness of the three primary colors.

What does the RGB color model look like?

Imagine that we sent rays of red, green and blue colors to one point on a white wall. A white spot will appear in the center, the intensity of colors at this point reaches 100%. In places where the rays touch, you will see new shades:

• green + blue - cyan (Cian)
• blue + red - magenta (Magenta)
• red + green - yellow (Yellow)

What is CMY (K)

These three colors underlie the CMYK color model - a subtractive model (from the English word subtraсt - "subtract"), which is based on the subtraction of primary colors from white: cyan subtracts red from white, yellow - blue, and magenta - green. The CMY (K) model is used in the printing industry for standard process printing and, in comparison with the RGB model, has a smaller color gamut. Paper and other printed materials are surfaces that reflect light. Agree, it is much more convenient to calculate how much light is reflected from a particular surface than to calculate how much is absorbed.

If you subtract three primary colors - RGB from white, you get three additional CMY colors.

An extra black has been added to the CMYK model for good reason. In theory, mixing the three primary colors should result in black. In reality, there are impurities in the paints, and instead of pure black, an indefinite dirty brown is obtained. Moreover, when printing, mixing three colors at once for the sake of obtaining black very much moisturizes the paper, the risk of waterlogging increases under not always ideal external conditions and due to the peculiarities of the dyes themselves. That is why black color was introduced into the model to obtain dark shades and directly the blackest. The letter K in the name of the CMYK model is taken from the word Black, and it denotes the key color - Key Color.

What is HSB?

Before we summarize, let's emphasize: RGB and CMYK models do not match the concept of color itself as well as the HSB color model. This is an abbreviation from English words: Hue, Saturation, Brightness - hue, saturation, brightness. HSB is based on the RGB model, but it has a different coordinate system: each color in this model is obtained by adding black or white paint to the main spectrum. In this case, the hue is the color itself, saturation is the percentage of white paint added to the color, and brightness is the percentage of black paint added.

The color description in this model does not match the colors perceived by the human eye. This model is used in graphic editors when customizing the color palette. Artists use it to carefully select shades.

What is the difference between RGB and CMYK?

So, let's summarize:

• RGB is the color model used to construct colors on the screen. Based on the addition of colors.
• CMYK is the color model used to form the image for printing. Based on subtraction of colors.

The difference between CMYK and RGB is that RGB is essentially just an emitted color (or light), while CMYK is a reflective color (ink). The first is formed due to the intensity of the glow, and the second is obtained as a result of overlaying paints in the printing industry. Accordingly, any images in electronic form - pictures on a computer monitor, photographs on a phone screen - are based on the RGB model. The CMYK model is used for full color printing. And so that the colors are not lost, the image is output from the additive model to the subtractive one before printing. Speaking in the language of designers and layout specialists, the CMYK model is a working tool of an offset printing house that prints colors onto paper.

CMYK and RGB: practical application

Typically, four inks are used for printing: cyan, magenta, yellow and black, which makes up the CMYK palette. Layouts for printing must be prepared in the CMYK color model, since in the process of outputting forms, the raster processor unambiguously interprets any color as a component of CMYK. It is important to remember that the CMYK color gamut is less than RGB, so all images, when preparing a layout for printing, require color correction and correct conversion to the CMYK color space.