What is a color model? Classification and characteristics of color models

The RGB model describes the colors emitted. It is based on three primary (basic) colors: red (Red), green (Green) and blue (Blue). The RGB model can be called “native” for the display. The remaining colors are obtained by combining the basic ones. This type of color is called additive.

From the figure it can be seen that the combination of green and red produces yellow, the combination of green and blue produces blue, and the combination of all three colors- white. From this we can conclude that colors in RGB are added subtractively.

Primary colors are taken from human biology. That is, these colors are based on the physiological reaction of the human eye to light. The human eye has photoreceptor cells that respond to most green (M), yellow-green (L) and blue-violet (S) light ( maximum length waves from 534 nm, 564 nm and 420 nm respectively). The human brain can easily distinguish a wide range of different colors based on differences in the signals received from the three waves.

Most widely RGB color the model is used in LCD or plasma displays such as a TV or computer monitor. Each pixel on a display can be represented by a hardware interface (e.g. graphic cards) as red, green and blue values. RGB values ​​vary in intensity, which are used for clarity. Cameras and scanners also work in the same way, they capture color with sensors that record different RGB intensities at each pixel.

In 16 bits per pixel mode, also known as Highcolor, there are either 5 bits per color (often referred to as 555 mode) or with an extra bit for green (known as 565 mode). The color green is added due to the fact that the human eye has the ability to detect more shades of green than any other color.

RGB values, represented in 24 bits per pixel (bpp) mode, also known as Truecolor, typically have three integer values ​​between 0 and 255. Each of these three numbers represents the intensity of red, green, and blue, respectively.

RGB has three channels: red, blue and green, i.e. RGB is a three-channel color model. Each channel can take values ​​from 0 to 255 in decimal or, more realistically, from 0 to FF in hexadecimal. This is explained by the fact that the byte with which the channel is encoded, and indeed any byte, consists of eight bits, and a bit can take 2 values ​​0 or 1, for a total of 28=256. In RGB, for example, red can have 256 gradations: from pure red (FF) to black (00). Thus, it is easy to calculate that the RGB model contains only 2563 or 16777216 colors.

RGB has three channels, and each is encoded with 8 bits. The maximum value, FF (or 255), gives a pure color. White color is obtained by combining all colors, or rather, their extreme gradations. Code white= FF(red) + FF(green) + FF(blue). Accordingly, black code = 000000. Yellow code = FFFF00, magenta = FF00FF, cyan = 00FFFF.

There are also 32 and 48 bit color display modes.

RGB is not used for printing on paper; instead, there is a CMYK color space.

CMYK is a color model used in color printing. A color model is a mathematical model for describing colors using integers. The CMYK model is based on cyan, magenta, yellow and black.

The color model (space) is understood as mathematical description diverse color range(spectrum), in other words, each specific color is assigned a digital digit. Almost all models are implemented using three colors (red, green, blue), it follows that each primary color has its own numerical description, all other colors are the result of digital generation of the primary ones.

All color models are different in type, where each has its own scope of application: RGB; HSB; Lab; CMY; CMYK; YIQ; YCC. Further, all the above models are divided into groups according to their operating structure, so RGB is the result of the addition of colors (additive class), CMY and CMYK are the opposite of the first and are embodied through the subtraction of colors (subtractive class), based on the perception of Lab, HSB, YIQ, YCC ( perceptual class).

The RGB base consists of red, green and blue, where when mixing each pair of primary colors, additional ones are obtained: yellow, cyan and magenta; by combining the primary and secondary colors, you can achieve almost any color shade.

The direct purpose of this model is to display the visible color range on your monitor. By default, the screen works in this mode, which beginners generally shouldn’t change.

Each color model has its own color gamut, i.e. the quantitative volume of colors that the human eye can discern and display on a device, such as a printer.

A serious problem with RGB is the lack of a large color gamut and hardware dependence (not quite the same display of colors on different mostly CRT monitors).

There are three subtypes of the model we are describing: sRGB has the smallest color gamut and is therefore suitable for those who work with web graphics. It is also suitable for printing, although on inkjet printers, it is not suitable for professional quality printing. Adobe RGB 1998 - derived from television standards, the most optimal look when working with graphics packages.

The latest Wide-Gamut RGB has the largest coverage and can be applied to 48-bit works. A computer monitor has a different principle for displaying colors, and therefore the RGB model (with its 3 types), to be honest, is almost unsuitable for printing.

But the CMY and CMYK color models are precisely designed to prepare an image and print it. The use of CMY (cyan, magenta, yellow) is justified only theoretically for black and white printers, where the cartridge can be replaced with a color one.

Adding black paint made it possible to make CMYK model(cyan, magenta, yellow, black) is fully functional (but not perfect) in color printing. The output quality of the range of gray shades has also improved. Like RGB, CMYK remains a hardware-dependent model with an insufficiently high color gamut.

With all its shortcomings, it quite adequately displays the spectrum necessary for printing, but at the same time it may have inadequate color rendition in the output, so it is better to initially edit some images in it. And yet, the quality obtained during printing directly depends on the quality of the paper!

In professional printing, CMYK is almost never used; they use its various modifications, which we will not mention; suffice it to say that these systems (Pantone, Trumatch, etc.) are integrated into serious graphics programs. That's it, incidentally, now let's move on.

The latest HSB color model and its ilk are simple, based on the rudimentary perception of brightness, hue and saturation, and are therefore hardware independent, using basic RGB color input, great for creating subtle spectral effects.

Each model reviewed has its own color gamut, which means that with some types of printing, color information cannot be completely accurately displayed on the monitor. Also, an uncalibrated or old display does not detect colors fully enough.

As a result, it is not always the right decision to select the desired color on the monitor. For correct selection There are special matching systems for colors. Such systems include reference color sets (atlases), necessary programs and devices for output calibration, as well as the so-called. palettes.

Custom (electronic) color tables are integrated into each professional graphic editor. All of them are focused on different ways presentation of your work, by the way, in Adobe they are called a catalog, in Corel they are called palettes. I think there is no great need to focus your attention on getting to know each of them, especially since they are intended mainly for designers and layout designers collaborating with the printing industry.

Moreover, some advanced users in this area use them when creating their own works and web design. In printing, multilayer, spot and combined (Spot colors) printing methods are used. It is the multilayer method that is based on the use of process dyes, which means that all color models in graphics packages work with process colors.

If the color model is program description, then the color mode is, so to speak, embodiment, implementation. The first mode is one-bit black and white graphics (Black and White (1-bit)) or bitmap, the simplest of all existing ones. To display it, you need only one bit of memory for each white and black pixel. It only applies to black and white images, and also in some cases, outputting a full-color image in black and white printing. Black and White has seven more varieties, all of them differ from each other in different software representations of the same one-bit graphics. The next Grayscale (8-bit) mode is an upgraded version previous regime by increasing the color resolution for each pixel to 8-bit and supporting up to 256 shades gray. New versions of programs also support 16-bit bit depth, for those who like to create in this interesting mode in its own way. An image in Duotone (8-bit) color mode is black and white image, enhanced with additional colors (from one to four). Duplex color mode consists of 256 shades of one (tone), two (two-tone), three (tri-tone) or four (quad) inks.

This mode is best used to add color to black and white images, as well as create all sorts of effects using various toning curve parameters. 24-bit natural mode RGB colors Color (24-bit) is designed to process full-color (color) images using 16.7 million colors, and can even use 48-bit resolution. RGB - the model works with color and alpha channels, and can also support layers (objects). Palette (Paletted) or Indexed Color (Indexed Color) is a simplified analogue of RGB Color, and therefore do not expect much realism in your “works” when practicing in this model. It is simply not capable of conveying all the color and tone nuances, but it also has its own niche in graphics. This model has subtypes.

There is not much to say about the CMYK Color mode; it is completely focused only on printing. Lab color mode is a 24-bit color mode in which all colors consist of three channels: brightness (L*- Luminosity), green/magenta (a*- green/magenta), blue/yellow (b*- blue/yellow ). Only halftone, RGB and CMYK images can be converted to Lab mode.

The internal model is useful for printing on Postscript Level 2 printers, processing PhotoCD, as well as for working with brightness, sharpness without distorting other color tones, and a number of other things that already established designers need. And the last color mode Multichannel is needed to display several color channels, where each channel carries 256 shades of gray. Suitable for converting drawings on a black and white printer; you can only work with an image that has more than one channel. NTSC RGB and PAL RGB modes are needed to convert pictures into video format.

When printing color computer maps in one way or another, the problem inevitably arises of ensuring accuracy in transmitting the original colors. This problem occurs for a variety of reasons.

Firstly, scanners And monitors work in an additive color model RGB, based on the rules of color addition, and printing is carried out in a subtractive model CMYK, in which the rules for subtracting colors apply.

Secondly, the methods of transmitting images on a computer monitor and on paper are different.

Thirdly, the reproduction process occurs in stages and is carried out on several devices, such as scanner, monitor, phototypesetting machine, which requires their adjustment in order to minimize color distortion throughout the entire technological cycle - process calibration.

RGB model.

RGB color model(Fig. 1) ( R-Red- red, G-Green- green, B - Blue- blue) is used to describe colors visible in transmitted or direct light. It is adequate to the color perception of the human eye. Therefore, the construction of images on monitor screens, in scanners, digital cameras and others optical instruments corresponds to the RGB model. In a computer RGB model, each primary color can have 256 brightness levels, which corresponds to 8-bit mode.

Rice. 1. RGB color model

Model CMY (CMYK)

CMY color model(Fig. 2) C-Cyan- blue, M - Magenta- purple, Y-Yellow- yellow, used to describe colors visible in reflected light (for example, the color of paint applied to paper). In theory, the sum of CMY colors at maximum intensity should produce pure black. In real practice, due to the imperfection of the coloring pigments of the paint and the initial instability to blue color In color separation, the sum of cyan, magenta and yellow colors produces a dirty brown color. Therefore, a fourth dye is also used in printing - black - blacK, which produces a rich, uniform black color. It is used for printing text and designing other important details, as well as for adjusting the overall tonal range of images. Color saturation in CMYK model measured as a percentage, so each color has 100 gradations of brightness.

The main task of the reproduction process is to convert the image from the model RGB into the model CMYK. This transformation is carried out using special software filters, taking into account all future printing settings: process ink system, dot gain coefficient, method of generating black color, ink balance and others. Thus, color separation is a complex process on which the quality of the final image largely depends. But even with optimal conversion from RGB V CMYK inevitably there is a loss of some shades. This is due to the different nature of these color models. It should also be noted that the models RGB And CMYK cannot convey the full spectrum of colors visible to the human eye.

Rice. 2. CMY color model

Model HSB.

Color can be characterized using other visual components. Yes, in the model HSB the basic color space is constructed according to three coordinates: color tone (Hue) ; saturation (Saturation) ; brightness (Brightness) . These parameters can be represented as three coordinates, which can be used to graphically determine the position of a visible color in color space.

Rice. 3. HSB color model

On the central vertical axis postponed brightness(Fig. 3), and on horizontal - saturation. The color tone corresponds to the angle at which saturation axis moves away from luminance axis. In the area of ​​the outer radius there are saturated, bright color tones, which, as they approach the center, mix and become less saturated. As you move along the vertical axis, colors of different hue and saturation become either lighter or darker.

In the center, where all the color tones mix, a neutral gray color is formed.

This color model fits well with human perception: color tone is the equivalent wavelength of light, saturation- wave intensity, and brightness characterizes the amount of light.

CIE system.

Color space can be used to describe the range of colors that are perceived by an observer or reproduced by a device. This range is called scale. This 3D format is also very convenient for comparing two or more colors. Three-dimensional color models and and three-digit color systems, such as RGB, CMY And HSB, are called three-coordinate colorimetric data.

Any measurement system requires a repeatable set of standard scales. For colorimetric measurements, the RGB color model is used as standard cannot be used because it unique- this space depends on specific device. Therefore, there was a need to create universal color system. Such a system is CIE. To obtain a set of standard colorimetric scales, in 1931 International Commission on Illumination- Commission Internationale de l'Eclairage (CIE) - approved several standard color spaces that describe the visible spectrum. With these systems, the color spaces of individual observers and devices can be compared against each other based on repeatable standards.

CIE color systems are similar to others 3D models discussed above, since in order to determine the position of a color in color space, they also use three coordinates. However, unlike those described above, the CIE spaces - that is, CIE XYZ, CIE L*a*b* and CIE L*u*v* - are device independent, meaning the range of colors that can be defined in these spaces is not limited to pictorial the capabilities of a particular device or the visual experience of a particular observer.

CIE XYZ.

The main CIE color space is the CIE XYZ space. It is built on the basis of the visual capabilities of the so-called standard observer, that is, a hypothetical viewer, whose capabilities were carefully studied and recorded during long-term studies of human vision conducted by the CIE commission. This system has three primary colors (red, green and blue) standardized along the wavelength and have fixed coordinates in the xy coordinate plane.

Based on the data obtained as a result of the research, a xyY color diagram was constructed - a chromatic diagram (Fig. 11).

All shades visible to the human eye are located inside a closed curve. The primary colors of the RGB model form the vertices of the triangle. This triangle contains the colors displayed on the monitor. The CMYK colors that can be reproduced in printing are enclosed within a polygon. The third coordinate, Y, is perpendicular to any point on the curve and displays the gradations of brightness of a particular color.

CIE Lab model

This model is created as an improved CIE model and is also hardware independent. The idea behind the Lab model is that each step in increasing the numerical value of one channel corresponds to the same visual perception as the other steps.

In the model Lab:

Magnitude L characterizes lightness (Lightness) (from 0 to 100%);

Index A defines color range on the color wheel from green to red (- 120 (green) to +120 (red));

Index b defines range from blue (-120) to yellow (+120).

At the center of the wheel, the color saturation is 0.

Lab's color gamut completely includes the color gamuts of all other color models and the human eye. Publishing programs use the Lab model as an intermediate when converting RGB to CMYK.

This article describes the color models used by the program Adobe Photoshop.

The world around us is full of all kinds of colors and shades of color. From a physical point of view, color is a set of specific wavelengths reflected from an object or transmitted through a transparent object. However, now we are interested not in the question of what color is, what its physical nature is, but in how one can obtain this or that color in practice. With the development of many industries, including printing and computer technology, the need for objective methods for describing and processing color has arisen.

Colors in nature are rarely simple. Most colors are made by mixing some other colors. For example, a combination of red and blue produces purple, and blue and green produces cyan. Thus, by mixing from a small amount simple flowers, you can get a lot (and quite a large one at that) of complex (composite) ones. Therefore, to describe color, the concept of a color model is introduced - as a way of representing a large number of colors by decomposing it into simple components.

Color wheel

One of these models is color wheel, which has already been mentioned several times before. It is shown in the figure and is called Oswald's big 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 secondary colors are located at the corners of an inverted triangle. A diagram of such a circle is presented below. Contrasting colors are located opposite each other.

Color gamut

Before we look at color models individually, let's first consider the concept of color gamut, which gives us an idea of ​​how well a particular color model represents colors. Color gamut is the maximum range of colors that a device or the human eye can reproduce or detect.

The cathode ray tube of a monitor or TV, color models, printing inks and, of course, the human eye have a certain color gamut. Figure 3 schematically shows a comparison of the color gamuts of the human eye, monitor and printing machine. The color gamut of the monitor approximately corresponds to the RGB model in various variations; the color gamut of the printing machine corresponds to CMYK.

So the color is computer technologies, in printing, in many other industries related to image processing, it is presented as a combination of a small number of three components. This representation is called a color model. Various types models have different color schemes. This is their main advantages or disadvantages. Reflected and absorbed color are described differently. There is quite large number color models, but we will focus only on those that are most often used in graphics packages.

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, projectors, and televisions. This color model is based on three primary colors: Red - red, Green - green and Blue - blue. Each of the above components can vary from 0 to 255, forming different colors and thus providing access to all 16 million. When working with the Adobe Photoshop graphic editor, we can choose a color, relying not only on what we see, but, if necessary, specify a digital value, thereby sometimes, especially when color correction, controlling the work process.

This color model is additive, that is, as the brightness of individual components increases, the brightness of the resulting color will also increase: if you mix all three colors with maximum intensity, the result will be white; on the contrary, in the absence of all colors the result is black.

Important to know: the numerical values ​​of the channels in Photoshop indicate the brightness of a given color. That is, than larger number, the lighter the channel looks. To better understand this fundamental principle, experiment with the color selection dialog box by typing different meanings one channel with zero others.

Advantages this mode is that it allows you to work with 16 million colors at 8 bits per channel (224 colors), but the disadvantage is that when the image is printed, some of these colors are lost, mainly the brightest and most saturated ones, and there is also a problem with blue flowers.

The RGB color model is considered the easiest to master. The vast majority of lessons for beginners and intermediate users are written specifically for it. But high level Proficiency in the Photoshop program requires knowledge of the basics and the ability to work in other color models.

CMYK color model

The CMYK color model is much closer to the color gamut of a printed image.

Unlike the previous RGB color model, this model uses the so-called subtractive color synthesis. It uses reflected light parameters. That is, if the color of an object, for example, is blue (Cyan), this means that it absorbs red from white, in other words, it is subtracted from white. If the object's color is purple (Magenta), it means it absorbs green. And finally, if the color of an object is yellow, then it absorbs blue light. If an object absorbs all colors, we see it as black. In the CMYK model, black is called the skeletal or key color. The abbreviation CMYK is formed by the first letters of subtractive colors.

Important to know: channels of the CMYK color model in Photoshop indicate the amount of paint a certain color. That is, the higher the numerical value of the channel, the darker it is. This is a fundamental difference between this model and the previous one. In addition, since CMYK contains 4 channels, it becomes possible for more subtle, even jewelry, color correction. This is why professional users prefer to perform color correction in this color model.

Preparing an image for printing in a printing house or on a printer also requires knowledge and ability to work in CMYK, since printing machines, including printers, create images exactly according to this principle.

The disadvantage of CMYK is that it has a narrower color gamut, so some colors are irretrievably lost when converted from another color model.

Lab color model

If there are usually no difficulties with previous color models, then with the Lab model the situation is completely different. Understanding the interaction of color channels in it is a little more difficult. The fact is that in the Lab space color is separated from contrast. One L (luminance) channel contains information about image detail and luminance contrast. This is almost a black and white version of the image. Channel a covers the palette from magenta (127) to green (-128). Channel b covers the palette from yellow (127) to blue (-128). Zero values ​​for a and b correspond to neutral tones, that is, all shades of gray.

Lab is also called a hardware-independent model. In fact, the entire work of the Photoshop program is based precisely on the algorithms of this color model (although most people are not aware of this). Lab's color gamut matches all the colors we see, so almost half of them are not reproduced in print, and a fifth are not reproduced by the monitor.

Mastering the work in Lab is not easy, but mastering even a few techniques of working in this space allows you to perform corrections that are either impossible to make in other models, or the result obtained in Lab in a few seconds is achieved with a lot of effort and time.

In conclusion, I would like to add that no matter what color space you choose to work with, this in itself does not mean anything. To achieve good result, you need to clearly know the principles of color formation for each model, and, of course, the basics of working with all the tools of the Photoshop program.

I wish you creative success!
Evgeniy Kartashov

Good day, dear readers, acquaintances, visitors, passing individuals and other strange creatures! Today we will talk about a slightly specific, but undoubtedly important thing for any user, namely this thing: the representation of color in a computer.

Whatever one may say, sooner or later everyone will be faced with the practical need to understand what a color model is, and simply this knowledge is useful from the point of view of broadening one’s horizons and awareness of what and how it works in a computer and what it consists of, both software and and from a physical point of view.

What is a color model

IN general view color model- this is some abstract thing in which color is represented as a collection of numbers. And each such model has its own characteristics and disadvantages. Essentially, it's like with language, for example, if the color is the word "house", then different languages it will be written and sounded differently, but the meaning of the word will be the same everywhere. It's the same with color.

We will look at the most basic models. Their 5 . As a rule, several are used simultaneously various models, because some are best used visually, while others are best used numerically.

RGB

This is the most common color representation model. In it, any color is considered as shades of three primary (or basic) colors: red, green (Green) and blue (Blue). There are two types of this model: eight-bit representation where the color is specified by numbers from 0 to 255 (for example color will correspond to blue, and - yellow), and sixteen-bit, which is most often used in graphic editors And html, where the color is specified by numbers from 0 to ff(green - # 00ff00, blue - # 0000ff, yellow - # ffff00).

The difference in ideas is that in eight-bit form, a separate scale is used for each base color, and in sixteen-bit color is immediately introduced. In other words, eight-bit presentation - three scales with each primary color, sixteen-bit- one scale with three colors.

The peculiarity of this model is that here a new color is obtained by adding shades of primary colors, i.e. "mixing".

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In the picture above you can see how the colors mix with each other to form new colors (yellow - [ 255,255,0 ], purple - [ 255,0,255 ], blue - [ 0,255,255 ] and white [ 255,255,255 ]).

Moreover, this model is most often used in numerical form, and not in visual form (when the color is set by entering its value in the corresponding field, and not selected with the mouse). For visual settings colors used other models. Because visually the model RGB is a three-dimensional cube, which, as you can see in the picture above, is not very convenient to use :)

So this is the most common model among web designers (we send our warm regards css) and programmers.

The disadvantage of this model is that it depends on the hardware, in other words, the same picture will look different on different monitors(because monitors use a so-called phosphor - a substance that converts the energy it absorbs into light radiation, and therefore, depending on the quality of this substance, the basic colors will be determined).

CMYK

This is also a very common model, but many may not have heard anything about it at all :)

And all due to the fact that it is used exclusively for printing. It stands for Cyan, Magenta, Yellow, Black(or Key Color), i.e. Cyan, Magenta, Yellow And Black(or key color).

The use of this model in printing is due to the fact that mixing three shades for each new color is too expensive and dirty, because When one color is first applied to paper, then another on top of it, and then a third color on top of them, firstly, the paper gets very wet (if inkjet printing), secondly, it is not at all a fact that you will get exactly the shade that you wanted. Yes, that's how physics works :)

The most attentive may have noticed that there are three colors in the picture, and black is obtained by mixing these three. So, why was he taken out separately? Again, the reason is that, firstly, mixing three colors is costly in terms of using toner (special powder for a printer cartridge, which is used instead of ink in laser printers), secondly, the paper gets very wet, which increases the drying time, thirdly, the colors may not actually mix properly, but may be more faded, for example. The picture below shows this model in reality

Thus, the result will not be black, but dirty gray or dirty brown.

That’s why (and not only) they introduced black color, so as not to stain the paper, not to spend money on toners, and in general to make life easier :)

The following animation very clearly illustrates the whole point (opens by clicking, weight approx. 14 Mb):

The color in this model is specified by numbers from 0 to 100 , where these numbers are often called "parts" or "portions" of the selected color. For example, khaki color is obtained by mixing 30 pieces of blue paint, 45 - purple, 80 - yellow and 5 - black, i.e. khaki color will be .

The difficulties of this model lie in the fact that in harsh realities (or in real harsh conditions) color depends not so much on numerical data as on the characteristics of the paper, the ink in the toner, the method of applying this ink, etc. So the numerical values ​​will clearly indicate the color on the monitor, but they will not show the actual picture on paper.

HSV (HSB) and HSL

I combined these two color models because... they are similar in principle.

3D implementation HSL(left) and HSV(right) models are presented in the form of a cylinder below, but in practice in the software ( software) is not used, because.. because it is three-dimensional :)

HSV (or HSB) means Hue, Saturation, Value(may also be called Brightness), Where:

• Hue- color tone, i.e. shade of color.
• Saturation- saturation. The higher this parameter, the “purer” the color will be, and the lower, the closer it will be to gray.
• Value(Brightness) - value (brightness) of color. The higher the value, the brighter the color will be (but not whiter). And the lower, the darker (0% - black)

HSL - Hue, Saturation, Lightness

• Hue- You already know
• Saturation- similar
• Lightness- this is the lightness of the color (not to be confused with brightness). The higher the parameter, the lighter the color (100% - white), and the lower, the darker (0% - black).

A more common model is HSV, it is often used together with the model RGB, Where HSV is shown visually, and numerical values ​​are specified in RGB. :

Here RGB- the model is circled in red and the shade values ​​are given by numbers from 0 to 255 , or you can immediately specify the color in hexadecimal form. And circled in blue HSV model (visual part in left rectangle, numeric - in right). You can also often specify opacity (called alpha channel).

This model is most often used in simple (or non-professional) image processing, because Using it, it’s convenient to adjust the basic parameters of photos without resorting to a bunch of different filters or individual settings.
For example, in everyone’s favorite (or cursed) Photoshop, both models are present, only one of them is in the color selection editor, and the other is in the settings window Hue/Saturation

Showing in red here RGB- model, blue - HSB, green - CMYK and blue Lab(more on her a little later), as can be seen in the picture :)
A HSL- The model is in a window like this:

Flaw HSB- model is that it also depends on the hardware. It simply does not correspond to the perception of the human eye, because... This model perceives colors with different brightness (for example, blue is perceived by us as darker than red), but in this model all colors have the same brightness. U HSL similar problems :)

They wanted to avoid such shortcomings, so one well-known company CIE(International Illumination Commission - Commission Internationale de l'Eclairage) came up with new model, designed to be independent of hardware. And they named her Lab(no, this is not an abbreviation for Laboratory).

Lab or L,a,b

This model is one of the standard ones, although it is little known to the average user.

It is deciphered as follows:

• L - Luminance- illumination (this is a combination of brightness and intensity)
• a- one of the components of color, changes from green to red
• b- the second of the color components, changes from blue to yellow

The figure shows the component ranges a And b For illumination 25% (left) and 75% (right)

The brightness in this model is separated from the colors, so it is convenient to use it to adjust contrast, sharpness and other light indicators without touching the colors :)

However, this model is not at all obvious to use and is quite difficult to use in practice. Therefore, it is used mainly in image processing and for converting them from one color model to another without loss (yes, this is the only model that does this without loss), but for ordinary mortal suffering users, as a rule, it is enough HSL And HSV plus filters.

Well, as an example of how the model works HSV, HSL And Lab here is a picture from Wikipedia (clickable)