I am a programmer by education, but at work I had to deal with image processing. And then an amazing and unexplored world of color spaces opened up for me. I don’t think that designers and photographers will learn something new for themselves, but perhaps this knowledge will turn out to someone, at least useful, and at best interesting.
The main purpose of color models is to make it possible to specify colors in a uniform manner. Essentially, color models define specific coordinate systems that allow you to uniquely define a color.
The most popular today are the following color models: RGB (used mainly in monitors and cameras), CMY (K) (used in printing), HSI (widely used in machine vision and design). There are many other models available. For example, CIE XYZ (standard models), YCbCr, etc. The following is a brief overview of these color models.
RGB color cube
The idea of an additive (i.e. based on mixing colors from directly emitting objects) color reproduction model arises from Grassmann's law. For the first time such a model was proposed by James Maxwell in 1861, but it became most widespread much later.In the RGB model (from the English red - red, green - green, blue - cyan) all colors are obtained by mixing three basic (red, green and blue) colors in different proportions. The share of each base color in the final color can be perceived as a coordinate in the corresponding three-dimensional space, therefore this model is often called a color cube. In Fig. 1 shows a model of a color cube.
Most often, the model is built so that the cube is single. The points corresponding to the base colors are located at the vertices of the cube lying on the axes: red - (1; 0; 0), green - (0; 1; 0), blue - (0; 0; 1). In this case, the secondary colors (obtained by mixing the two basic ones) are located in other vertices of the cube: cyan - (0; 1; 1), magenta - (1; 0; 1) and yellow - (1; 1; 0). Black and white colors are located at the origin (0; 0; 0) and the point farthest from the origin (1; 1; 1). Rice. only shows the tops of the cube.
Color images in the RGB model are built from three separate image channels. Table. the decomposition of the original image into color channels is shown.
In the RGB model, a certain number of bits are allocated for each color component, for example, if 1 byte is allocated for encoding each component, then using this model you can encode 2 ^ (3 * 8) ≈16 million colors. In practice, such coding is redundant, since most people cannot distinguish that many colors. Often limited to the so-called. mode "High Color" in which 5 bits are allocated for encoding each component. In some applications, a 16-bit mode is used in which 5 bits are allocated for encoding R and B components, and 6 bits for encoding G components. This mode, firstly, takes into account the higher human sensitivity to green color, and secondly, allows more efficient use of the features of the computer architecture. The number of bits allocated for encoding one pixel is called the color depth. Table. examples of encoding the same image with different color depths are given.
Subtractive CMY and CMYK models
The subtractive CMY model (from the English cyan - cyan, magenta - magenta, yellow - yellow) is used to obtain hard copies (printing) of images, and in some way is the antipode of the RGB color cube. If in the RGB model the base colors are the colors of the light sources, then the CMY model is the color absorption model.For example, paper coated with yellow dye does not reflect blue light; we can say that the yellow dye subtracts blue from the reflected white light. Similarly, cyan dye subtracts red from reflected light, and magenta dye subtracts green. That is why this model is usually called subtractive. The algorithm for converting from RGB to CMY is very simple:
This assumes that RGB colors are in the range. It is easy to see that to get black in the CMY model, you need to mix cyan, magenta and yellow in equal proportions. This method has two serious drawbacks: firstly, the black color obtained as a result of mixing will look lighter than "real" black, and secondly, this leads to significant dye costs. Therefore, in practice, the CMY model is expanded to the CMYK model, adding black to the three colors.
Color space hue, saturation, intensity (HSI)
The previously considered RGB and CMY (K) color models are very simple in terms of hardware implementation, but they have one significant drawback. It is very difficult for a person to operate with the colors specified in these models, because a person, describing colors, uses not the content in the described color of the basic components, but somewhat different categories.Most often, people operate with the following concepts: hue, saturation and lightness. In this case, when talking about a color tone, they usually mean exactly the color. Saturation shows how much the described color is diluted with white (pink, for example, is a mixture of red and white). The concept of lightness is the most difficult to describe, and with some assumptions, lightness can be understood as the intensity of light.
If we consider the projection of the RGB cube in the direction of the diagonal white-black, we get a hexagon:
All gray colors (lying on the diagonal of the cube) are projected to the center point. To use this model to encode all the colors available in the RGB model, you need to add a vertical axis of lightness (or intensity) (I). The result is a hexagonal cone:
In this case, the hue (H) is set by the angle relative to the red axis, the saturation (S) characterizes the purity of the color (1 means completely pure color, and 0 corresponds to a shade of gray). It is important to understand that hue and saturation are not defined at zero intensity.
The RGB to HSI conversion algorithm can be performed using the following formulas:
The HSI color model is very popular among designers and artists because this system provides direct control of hue, saturation, and brightness. These same properties make this model very popular in machine vision systems. Table. shows the change in the image with increasing and decreasing the intensity, tone (rotated by ± 50 °) and saturation.
Model CIE XYZ
With the aim of unification, an international standard color model has been developed. As a result of a series of experiments, the International Commission on Illumination (CIE) determined the addition curves of the primary (red, green and blue) colors. In this system, each visible color corresponds to a certain ratio of primary colors. At the same time, in order for the developed model to reflect all the colors visible to a person, it was necessary to introduce a negative amount of basic colors. To get away from negative values, the CIE introduced the so-called. unreal or imaginary primary colors: X (imaginary red), Y (imaginary green), Z (imaginary blue).When describing color, the X, Y, Z values are called standard basic excitations, and the coordinates obtained from them are called standard color coordinates. Standard addition curves X (λ), Y (λ), Z (λ) (see Fig.) Describe the sensitivity of the average observer to standard excitations:
In addition to standard color coordinates, the concept of relative color coordinates is often used, which can be calculated using the following formulas:
It is easy to see that x + y + z = 1, which means that any pair of values is sufficient for the unambiguous assignment of relative coordinates, and the corresponding color space can be represented as a two-dimensional graph:
The set of colors defined in this way is called the CIE triangle.
It is easy to see that the CIE triangle describes only hue, but does not describe brightness in any way. To describe the brightness, an additional axis is introduced, passing through a point with coordinates (1/3; 1/3) (the so-called white point). The result is a CIE color body (see Fig.):
This body contains all the colors visible to the average observer. The main disadvantage of this system is that using it, we can only state the coincidence or difference of two colors, but the distance between two points of this color space does not correspond to the visual perception of the difference in colors.
Model CIELAB
The main goal in the development of CIELAB was to eliminate the non-linearity of the CIE XYZ system from the point of view of human perception. The abbreviation LAB usually refers to the CIE L * a * b * color space, which is currently an international standard.In the CIE L * a * b system, the L coordinate means lightness (in the range from 0 to 100), and the a, b coordinates mean the position between green-magenta and blue-yellow colors. Formulas for converting coordinates from CIE XYZ to CIE L * a * b * are given below:
where (Xn, Yn, Zn) are the coordinates of the white point in the CIE XYZ space, and
In Fig. cuts of the CIE L * a * b * color body are presented for two lightness values:
Compared to CIE XYZ system Euclidean distance (√ ((L1-L2) ^ 2 + (a1 ^ * - a2 ^ *) ^ 2+ (b1 ^ * - b2 ^ *) ^ 2)) in CIE L * a * b * significantly better matches human perceived color difference, however, the standard formula for color difference is the extremely complex CIEDE2000.
TV color difference color systems
In the YIQ and YUV color systems, color information is represented as a luminance signal (Y) and two color-difference signals (IQ and UV, respectively).The popularity of these color systems is primarily due to the advent of color television. Because the Y component essentially contains the original image in grayscale, the signal in the YIQ system could be received and correctly displayed both on old black-and-white TVs and on new color ones.
The second, perhaps more important, advantage of these spaces is the separation of information about the color and brightness of the image. The fact is that the human eye is very sensitive to changes in brightness, and much less sensitive to changes in chromaticity. This allows the transmission and storage of color information with reduced depth. It is on this feature of the human eye that the most popular image compression algorithms (including jpeg) are built today. To convert from RGB to YIQ space, you can use the following formulas:
Brightness of color is a characteristic of perception. It is determined by our speed of distinguishing one tone from the background of others.
This is a relative characteristic, it can only be known by comparison. Complex shades, with an admixture of gray or brown, create the necessary contrast for our eyes to highlight the tones that are most suitable for this definition.
Bright tones are shades close to the pure spectrum. If the surface of the material reflects one or another wave (c) with the least distortion, then we consider that this tone is bright.
Admixture of white or black does not significantly affect the brightness of the color. So burgundy can be quite bright as well as light yellow. Yellow-green is also a catchy tone, like an intermediate wavelength between green and yellow.
Each spectrum has its own lightness: bright yellow is the lightest; the darkest are blue and purple.
Intermediate are: blue, green, pink, red.
This statement is true if we consider a line of shades of the same color.
If you single out the brightest shade among other tones, then the brighter will be the color that differs as much as possible in lightness from the rest.
Bright shades set a contrast with dimmer, darker or lighter ones, due to which we consider the combination to be saturated, expressive.
USEFUL ARTICLES ON THIS TOPIC (click on the picture)
Color plays a huge role not only in art, but also in everyday life. Few people think about how strongly different combinations of shades affect human perception, mood and even thinking. This is a kind of phenomenon that operates according to its seemingly ghostly, but clear laws. Therefore, it is not so difficult to subordinate him to his will so that he works for the good: you just have to figure out how he works.
Concept
Color is a subjective characteristic of electromagnetic radiation in the optical range, which is determined based on the resulting visual impression. The latter depends on many physiological and psychological reasons. His understanding can be equally influenced by his spectral composition and the personality of the perceiving person.
To put it more simply, color is the impression that a person receives when a beam of light rays penetrates the retina. A ray of light with the same spectral composition can cause different sensations in different people due to the distinctive features of the sensitivity of the eye, therefore, the shade can be perceived differently for each person.
Physics
Color vision that appears in the mind of a person includes semantic content. The tone appears during the absorption of light waves: for example, a blue ball looks like this only because the material from which it is created absorbs all shades of the light beam, except for the blue, which it reflects. Therefore, when we talk about a blue ball, we only mean that the molecular composition of its surface is capable of absorbing all colors of the spectrum, except for blue. The ball itself has no tone, like any object on the planet. Color is born only in the process of illumination, in the process of perception of waves by the eye and processing of this information by the brain.
A clear distinction of hue and its basic characteristics between the eyes and the brain can be achieved through comparison. Therefore, the values can only be determined by comparing the color with another achromatic shade, including black, white and gray. The brain is also able to compare hue to other chromatic tones in the spectrum by analyzing the hue. Perception refers to a psychophysiological factor.
Psychophysiological reality is, in fact, a color effect. The hue and its effect can coincide when using harmonic midtones - in other situations, the color can be modified.
It is important to know the basic characteristics of flowers. This concept includes not only its actual perception, but also the influence of various factors on it.
Basic and additional
Mixing certain pairs of colors can give the impression of white. Complementary tones are opposite tones that, when mixed, give gray. The RGB triad is named after the main colors of the spectrum - red, green and blue. Additional in this case will be cyan, purple and yellow. On the color wheel, these shades are located in opposition, opposite each other so that the values of the two color triplets alternate.
Let's talk in more detail
The main physical characteristics of color include the following points:
- brightness;
- contrast (saturation).
Each characteristic can be quantified. The fundamental differences in the basic characteristics of color are that brightness means lightness or darkness. This is the content in it of a light or dark component, black or white, while contrast informs information about the content of a gray tone: the less it is, the higher the contrast.
Also, any shade can be specified by three peculiar coordinates that represent the main characteristics of a color:
- lightness;
- saturation.
These three indicators are able to determine a specific shade, starting from the main tone. The main characteristics of color and their fundamental differences are described by the science of color, which is engaged in a deep study of the properties of this phenomenon and its influence on art and life.
Tone
The color characteristic is responsible for the location of the hue in the spectrum. The chromatic tone is somehow referred to as one or another part of the spectrum. Thus, shades that are in the same part of the spectrum (but differ, for example, in brightness) will belong to the same tone. When changing the position of a shade along the spectrum, its color characteristic changes. For example, shifting blue towards green changes the tone to cyan. Moving in the opposite direction, blue will tend to red, taking on a purple hue.
Coldness
Often, the change in tone is associated with the warmth of the color. Red, red and yellow shades are classified as warm, associating them with fiery, "warming" colors. They are associated with the corresponding psychophysical reactions in human perception. Blue, purple, blue symbolize water and ice, referring to cold shades. The perception of "warmth" is associated with both physical and psychological factors of an individual personality: preferences, mood of the observer, his psycho-emotional state, adaptation to environmental conditions, and much more. Red is considered the warmest, blue is the coldest.
It is also necessary to highlight the physical characteristics of the sources. Color temperature is largely associated with the subjective feeling of warmth of a particular shade. For example, the tone of thermal study as the temperature rises passes over the "warm" tones of the spectrum from scarlet to yellow and finally white. However, cyan has the highest color temperature, which is nevertheless considered a cold shade.
Activity is also among the main characteristics within the hue factor. Red is said to be the most active, while green is the most passive. This characteristic can also change somewhat under the influence of the subjective gaze of different people.
Lightness
Shades of the same hue and saturation can refer to different degrees of lightness. Consider this characteristic in mind of blue. With the maximum value of this characteristic, it will be close to white, having a delicate bluish tint, and with a decrease in the value, blue will become more and more similar to black.
Any tone will turn black when the lightness is lowered, and white when the lightness is increased.
It should be noted that this indicator, like all other basic physical characteristics of color, can largely depend on subjective conditions associated with the psychology of human perception.
By the way, shades of different tones, even with the same actual lightness and saturation, are perceived by a person differently. Yellow is in fact the lightest, while blue is the darkest shade in the chromatic spectrum.
With a high characteristic, yellow differs from white even less than blue is distinguishable from black. It turns out that the yellow tone has even greater lightness of its own than "darkness" is characteristic of blue.
Saturation
Saturation is the level of difference of a chromatic hue from an achromatic equal in lightness. In fact, saturation is a characteristic of depth, color purity. Two shades of the same tone can have different levels of fading. As the saturation decreases, any color will become closer to gray.
Harmony
Another of the common characteristics of color, which describes the human experience of combining several shades. Each person is endowed with their own preferences and tastes. Therefore, people have different ideas about the harmony and disharmony of different types of colors (with color characteristics inherent in them). Harmonious combinations are called similar in tone or shades from different intervals of the spectrum, but with a similar lightness. As a rule, harmonious combinations do not have high contrast.
As for the rationale for this phenomenon, this concept should be considered in isolation from subjective opinions and personal tastes. The impression of harmony arises under the conditions of the fulfillment of the law on complementary colors: the equilibrium state corresponds to a gray tone of medium lightness. It is obtained not only by mixing black and white, but also by a pair of additional shades, if they contain the main colors of the spectrum in a certain proportion. All combinations that do not give gray when mixed are considered disharmonious.
Contrasts
Contrast is the difference between two shades, found out by comparing them. Studying the main characteristics of color and their fundamental differences, seven types of contrast manifestations can be identified:
- Contrast of comparisons. The most pronounced are variegated blue, yellow and red. As you move away from these three tones, the intensity of the shade decreases.
- Contrast of dark and light. There is the lightest and the darkest shades of the same color, and in between there are countless manifestations.
- Contrast of cold and warm. Red and blue are recognized as poles of contrast, and other colors can be warmer or colder in accordance with how they relate to other cold or warm tones. This contrast is only known by comparison.
- Contrast complementary colors - those shades that, when mixed, give a neutral gray. Opposing tones need each other to balance. Couples have their own types of contrasts: yellow and violet are the contrast of light and dark, and red-orange and blue-green are warmth.
- Simultaneous contrast is simultaneous. This is a phenomenon in which the eyes, when perceiving a particular color, need an additional shade, and in its absence, it generates it on its own. Simultaneously generated shades are an illusion that does not exist in reality, but it creates a special impression from the perception of color combinations.
- Saturation contrast characterizes the opposite of saturated colors with faded ones. The phenomenon is relative: a tone, even if not pure, may appear brighter next to a faded shade.
- Color spreading contrast describes the relationship between color planes. It has the ability to enhance the manifestation of all other contrasts.
Spatial impact
Color has properties that can affect the perception of depth through the contrasts of dark and light, and by changes in saturation. For example, all light tones against a dark background will visually protrude forward.
As for warm and cold shades, warm tones will come to the fore, and cold tones will go deeper.
Saturation contrasts bring out vibrant colors against muted hues.
Spread contrast, also called color plane magnitude contrast, plays a huge role in the illusion of depth.
Color is an amazing phenomenon in this world. It is capable of influencing perception, deceiving the eye and the brain. But if you figure out how this phenomenon works, you can not only maintain clarity of perception, but also make it so that color becomes a faithful assistant in life and art.
Each color has three main properties: hue, saturation, and lightness.
In addition, it is important to know about such characteristics of color as light and color contrasts, to get acquainted with the concept of the local color of objects and to feel some spatial properties of color.
Color tone
In our minds, the color tone is associated with the color of well-known objects. Many color names come directly from objects with a characteristic color: sandy, aqua, emerald, chocolate, coral, raspberry, cherry, cream, etc.
It is easy to guess that the hue is determined by the name of the color (yellow, red, blue, etc.) and depends on its place in the spectrum.
It is interesting to know that a trained eye in bright daylight distinguishes up to 180 color tones and up to 10 levels (gradations) of saturation. In general, the developed human eye is able to distinguish about 360 shades of color.
67. Children's holiday of color
Color saturation
Color saturation is the difference between a chromatic color and a gray color equal to it in lightness (Fig. 66).
If you add gray paint to any color, the color will fade, its saturation will change.
68. D. MORANDI. Still life. An example of a muted color scheme
69. Change color saturation
70. Changing the saturation of warm and cold colors
Lightness
The third sign of color is lightness. Any colors and shades, regardless of the color tone, can be compared in terms of lightness, that is, to determine which of them is darker and which is lighter. You can change the lightness of the color by adding white or water to it, then red will turn pink, blue - blue, green - light green, etc.
71. Changing the lightness of color using white
Lightness is a quality inherent in both chromatic and achromatic colors. Lightness should not be confused with whiteness (as the quality of an object's color).
It is customary for artists to call light relations tonal, therefore, one should not confuse light and color tone, cut-off and color structure of the work. When they say that a picture is painted in light colors, then first of all they mean light relationships, and in color it can be gray-white, and pinkish-yellow, light lilac, in a word very different.
Differences of this type are called valers by painters.
Any colors and shades can be compared in terms of lightness: pale green with dark green, pink with blue, red with purple, etc.
It is interesting to note that red, pink, green, brown and other colors can be both light and dark colors.
72. Difference of colors by lightness
Due to the fact that we remember the colors of the objects around us, we imagine their lightness. For example, a yellow lemon is lighter than a blue tablecloth, and we remember that yellow is lighter than blue.
Achromatic colors, that is, gray, white and black, are characterized only by lightness. The differences in lightness are that some colors are darker while others are lighter.
Any chromatic color can be compared in lightness with an achromatic color.
Consider the color wheel (Fig. 66), consisting of 24 colors.
You can compare the colors: red and gray, pink and light gray, dark green and dark gray, purple and black, etc. Achromatic colors are matched in lightness to equal chromatic ones.
Light and color contrasts
The color of an item constantly changes depending on the conditions in which it is found. Lighting plays a huge role in this. See how the same object changes unrecognizably (Fig. 71). If the light on an object is cold, its shadow appears warm and vice versa.
The contrast of light and color is most clearly and clearly perceived at the "break" of the form, that is, at the place of the turn of the shape of objects, as well as at the boundaries of contact with the contrasting background.
73. Light and color contrasts in still lifes
Light contrast
Artists use contrast in lightness, emphasizing the different tonality of objects in the image. Placing light objects next to dark ones, they enhance the contrast and sonority of colors, and achieve expressive form.
Compare the same gray squares on a black and white background. They will seem different to you.
Gray appears lighter on black, and darker on white. This phenomenon is called light contrast or lightness contrast (Fig. 74).
74. An example of contrast in lightness
Colour contrast
We perceive the color of objects depending on the surrounding background. The white tablecloth will appear blue if you put orange oranges on it, and pink if it contains green apples. This is because the background color takes on a complementary color to the color of the objects. A gray background appears cool next to a red object, and a warm background next to blue and green.
75. An example of color contrast
Consider silt. 75: all three gray squares are the same, on a blue background, gray becomes orange, on yellow - purple, on green - pink, that is, it acquires a shade of a complementary color to the background color. On a light background, the color of the subject appears darker, on a dark background - light.
The phenomenon of color contrast is that a color changes under the influence of other surrounding colors, or under the influence of colors previously observed.
76. An example of color contrast
Complementary colors in the vicinity of each other become brighter and richer. The same happens with the primary colors. For example, a red tomato will look even redder next to parsley, and purple eggplant next to yellow turnips.
The contrast of blue and red is a prototype of the contrast of cold and warm. It underlies the color of many works of European painting and creates a dramatic tension in the paintings of Titian, Poussin, Rubens, A. Ivanov.
Contrast as the opposition of colors in a painting is the main method of artistic thinking in general, asserts N. Volkov, a famous Russian artist and scientist *.
In the reality around us, the effects of one color on another are more complex than in the examples considered, but knowledge of the main contrasts - in lightness and color - helps the painter to better see these relationships of colors in reality and use the knowledge gained in practical work. The use of light and color contrasts increases the possibilities of visual media.
77. Umbrellas. An example of using color nuances
78. Balloons. An example of using color contrasts
Tone and color contrasts are of particular importance for achieving expressiveness in decorative work.
Color contrast in nature and decorative art:
a. M. ZVIRBULE. Tapestry "Together with the Wind"
b. Peacock feather. Photo
v. Autumn leaves. Photo
Poppy field. Photo
D. ALMA THOMAS. The blue light of infancy
Local color
Examine the objects in your room, look out the window. Everything that you see has not only shape, but also color. You can easily identify it: the apple is yellow, the cup is red, the tablecloth is blue, the walls are blue, etc.
The local color of an object is those pure, unmixed, unreflected tones that, in our view, are associated with certain objects, as their objective, unchanging properties.
Local color is the main color of an object, excluding external influences.
The local color of an object can be monochromatic (Fig. 80), but it can also consist of different shades (Fig. 81).
You will see that the main color of roses is white or red, but in each flower you can count several shades of local color.
80. Still life. Photo
81. VAN BEIEREN. Vase with Flowers
When drawing from nature, from memory it is necessary to convey the characteristic features of the local color of objects, its changes in light, in partial shade and in shadow.
Under the influence of light, air, combination with other colors, the same local color acquires a completely different tone in the shade and in the light.
In sunlight, the color of the objects themselves is seen best in places where penumbra is located. The local color of objects is less visible where there is a full shadow on it. It lightens and becomes discolored in bright light.
Artists, by showing us the beauty of objects, accurately determine the changes in local color in light and in shadow.
Once you master the theory and practice of using primary, composite and complementary colors, you can easily convey the local color of an object, its shades in the light and in the shade. In the shadow cast by the object or located on it, there will always be a color that is complementary to the color of the object itself. For example, in the shade of a red apple, green will definitely be present, as an additional color to red. In addition, each shadow contains a tone slightly darker than the color of the object itself, and a blue tone.
82. Scheme for obtaining the color of the shadow
It should not be forgotten that the local color of an object is influenced by its environment. When a green drapery appears next to a yellow apple, a colored reflex appears on it, that is, the apple's own shadow necessarily acquires a shade of green.
83. Still life with yellow apple and green drapery
Hue (hue of a color) is indicated by terms such as yellow, green, blue, etc. Saturation is the degree or strength of expression of a hue. This color characteristic indicates the amount of paint or the concentration of the dye.
Lightness is a sign that allows you to compare any chromatic color with one of the gray colors, called achromatic.
Qualitative characteristic of chromatic color:
· Color tone
Lightness
· Saturation. (Figure 8)
Color tone defines the name of a color: green, red, yellow, blue, etc. This is a color quality that allows you to compare it with one of the spectral or magenta colors (except chromotic) and give it a name.
Lightness is also a color property. The light ones include yellow, pink, blue, light green, etc., the dark ones - blue, purple, dark red, and other colors.
Lightness characterizes how much a particular chromatic color is lighter or darker than another color, or how close a given color is to white.
This is the degree to which a given color differs from black. It is measured by the number of thresholds of difference from a given color to black. The lighter the color, the higher its lightness. In practice, it is customary to replace this concept with the concept of "brightness".
Term saturation color is determined by its (color) proximity to the spectral. The closer the color to the spectral, the more saturated it is. For example, lemon yellow, orange - orange, etc. The color loses its saturation from the admixture of white or black paint.
Color saturation characterizes the degree of difference between a chromatic color and an achromatic color equal to it in terms of lightness.
COLOR TONE SATURATION LIGHTNESS
Color tone determines the place of color in the spectrum ("red-green-yellow-blue") This is the main characteristic of color. In a physical sense, COLOR TONE depends on the wavelength of light. Long waves are the red part of the spectrum. Short - shift towards the blue-violet side. Medium wavelengths are yellow and green, which are most optimal for the eye.
There are ACHROMATIC colors. It's black, white, and the whole gray scale in between. They don't have a TONE. Black is the absence of color, white is a mixture of all colors. Grays are usually obtained by mixing two or more colors. All others are CHROMATIC colors.
The degree of chromaticity of the color is determined saturation... This is the degree to which a color is removed from a gray of the same lightness. Imagine dust covering the fresh grass by the road, layer by layer. The more layers of dust, the less visible the original pure green color, the less SATURATION of this green. The colors with the maximum saturation are spectral colors, the minimum saturation gives full achromatic (no hue).
Lightness (brightness) - this is the position of the color on a scale from white to black. It is characterized by the words "dark", "light". Compare the color of coffee and the color of coffee with milk. The maximum LIGHT is white, the minimum is black. Some colors are initially (spectrally) lighter - (yellow). Others are darker (blue).
In photoshep: The next system used in computer graphics is the system HSB... Raster formats do not use the system HSB for storing images, since it contains only 3 million colors.
In system HSB color decomposes into three components:
- HUE(Hue) - The frequency of the wave of light bouncing off the object you see.
- SATURATION(Saturation) is the purity of a color. This is the ratio of the main tone and colorless gray equal in brightness. The most saturated color contains no gray at all. The lower the saturation of the color, the more neutral it is, the more difficult it is to unambiguously characterize it.
· BRIGHTNESS(Brightness) is the overall brightness of a color. The minimum value of this parameter turns any color to black. ... (Figure 9)
(Figure 10)
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