Physics of perception. Physiology of color perception The general influence of color on the physical and mental state of a person

Color perception(color sensitivity, color perception) - the ability of vision to perceive and transform light radiation of a certain spectral composition into the sensation of various color shades and tones, forming a holistic subjective sensation (“chromaticity”, “chromaticity”, coloring).

Color is characterized by three qualities:

• color tone, which is the main characteristic of color and depends on the wavelength of light;
• saturation, determined by the proportion of the main tone among impurities of a different color;
• brightness, or lightness, which is manifested by the degree of proximity to white (the degree of dilution with white).

The human eye only notices color changes when the so-called color threshold (the minimum color change noticeable to the eye) is exceeded.

The physical essence of light and color

Visible electromagnetic vibrations are called light or light radiation.

Light emissions are divided into complex And simple.

White sunlight is complex radiation, which consists of simple color components - monochromatic (one-color) radiation. The colors of monochromatic radiation are called spectral.

If a white beam is decomposed into a spectrum using a prism, you can see a series of continuously changing colors: dark blue, blue, cyan, blue-green, yellow-green, yellow, orange, red.

The color of the radiation is determined by the wavelength. The entire visible spectrum of radiation is located in the wavelength range from 380 to 720 nm (1 nm = 10 -9 m, i.e. one billionth of a meter).

The entire visible part of the spectrum can be divided into three zones

• Radiation with a wavelength from 380 to 490 nm is called the blue zone of the spectrum;
• from 490 to 570 nm - green;
• from 580 to 720 nm - red.

A person sees different objects painted in different colors because monochromatic radiation is reflected from them in different ways, in different proportions.

All colors are divided into achromatic And chromatic

• Achromatic (colorless) are gray colors of varying lightness, white and black. Achromatic colors are characterized by lightness.
• All other colors are chromatic (colored): blue, green, red, yellow, etc. Chromatic colors are characterized by hue, lightness and saturation.

Color tone- this is a subjective characteristic of color, which depends not only on the spectral composition of the radiation entering the observer’s eye, but also on the psychological characteristics of individual perception.

Lightness subjectively characterizes the brightness of a color.

Brightness determines the intensity of light emitted or reflected from a unit surface in a direction perpendicular to it (unit of brightness - candela per meter, cd/m).

Saturation subjectively characterizes the intensity of the sensation of color tone.
Since not only the radiation source and the colored object, but also the eye and brain of the observer are involved in the occurrence of the visual sensation of color, some basic information about the physical essence of the process of color vision should be considered.

Perception of color by the eye

It is known that the eye is similar in structure to a camera, in which the retina plays the role of a photosensitive layer. Radiations of various spectral compositions are recorded by retinal nerve cells (receptors).

Receptors that provide color vision are divided into three types. Each type of receptor absorbs radiation differently from the three main zones of the spectrum - blue, green and red, i.e. has different spectral sensitivity. If blue zone radiation hits the retina, it will be perceived by only one type of receptor, which will transmit information about the power of this radiation to the observer’s brain. The result will be a blue sensation. The process will proceed similarly if the retina of the eye is exposed to radiation from the green and red zones of the spectrum. When two or three types of receptors are simultaneously excited, a color sensation will arise, depending on the ratio of the radiation powers of different zones of the spectrum.

With the simultaneous stimulation of receptors that detect radiation, for example, the blue and green zones of the spectrum, a light sensation may arise, from dark blue to yellow-green. The sensation of more blue shades of color will occur in the case of greater radiation power in the blue zone, and green shades - in the case of greater radiation power in the green zone of the spectrum. Equal radiation power from the blue and green zones will cause a sensation of blue color, green and red zones - a sensation of yellow color, red and blue zones - a sensation of purple color. Cyan, magenta and yellow are therefore called dual-zonal colors. Equal radiation power from all three zones of the spectrum causes the sensation of gray color of varying lightness, which turns into white with sufficient radiation power.

Additive light synthesis

This is the process of obtaining different colors by mixing (adding) radiation from the three main zones of the spectrum - blue, green and red.

These colors are called the main or primary radiations of adaptive synthesis.

Different colors can be produced in this way, for example, on a white screen using three projectors with filters of blue (Blue), green (Green) and red (Red). In areas of the screen illuminated simultaneously from different projectors, any colors can be obtained. The color change is achieved by changing the ratio of the power of the main radiations. The addition of radiation occurs outside the observer's eye. This is one of the types of additive synthesis.

Another type of additive synthesis is spatial displacement. Spatial displacement is based on the fact that the eye does not distinguish separately located small multi-colored image elements. Such, for example, as raster dots. But at the same time, small image elements move across the retina of the eye, so the same receptors are successively affected by different radiation from neighboring differently colored raster dots. Due to the fact that the eye does not distinguish between rapid changes in radiation, it perceives them as the color of a mixture.

Subtractive color synthesis

This is the process of obtaining colors by absorbing (subtracting) radiation from white color.

In subtractive synthesis, a new color is obtained using paint layers: cyan (Cyan), magenta (Magenta) and yellow (Yellow). These are the primary or primary colors of subtractive synthesis. Cyan ink absorbs (subtracts from white) red radiation, magenta absorbs green, and yellow absorbs blue.

In order to obtain, for example, red color using a subtractive method, you need to place yellow and magenta light filters in the path of white radiation. They will absorb (subtract) blue and green radiation, respectively. The same result will be obtained if yellow and purple paints are applied to white paper. Then only red radiation will reach the white paper, which is reflected from it and enters the eye of the observer.

• The main colors of additive synthesis are blue, green and red and
• The primary colors of subtractive synthesis - yellow, magenta and cyan - form pairs of complementary colors.

Complementary colors are the colors of two radiations or two colors that, when mixed, make an achromatic color: F + S, P + Z, G + K.

With additive synthesis, additional colors give gray and white colors, since in total they represent radiation from the entire visible part of the spectrum, and with subtractive synthesis, a mixture of these colors gives gray and black colors, since the layers of these colors absorb radiation from all zones of the spectrum.

The considered principles of color formation also underlie the production of color images in printing. To obtain printed color images, so-called process printing inks are used: cyan, magenta and yellow. These paints are transparent and each of them, as already indicated, subtracts the radiation of one of the spectrum zones.

However, due to the imperfection of the components of subtactive synthesis, a fourth additional black ink is used in the manufacture of printed products.

It can be seen from the diagram that if process paints are applied to white paper in various combinations, then all the basic (primary) colors can be obtained for both additive and subtractive synthesis. This circumstance proves the possibility of obtaining colors with the required characteristics when producing color printed products using process inks.

Changes in the characteristics of the reproduced color occur differently depending on the printing method. In gravure printing, the transition from light areas of the image to dark ones is carried out by changing the thickness of the ink layer, which allows you to adjust the basic characteristics of the reproduced color. In gravure printing, color formation occurs subtractively.

In letterpress and offset printing, the colors of different areas of the image are transmitted by raster elements of various sizes. Here, the characteristics of the reproduced color are regulated by the sizes of the raster elements of different colors. It was already noted earlier that colors in this case are formed by additive synthesis - spatial mixing of the colors of small elements. However, where halftone dots of different colors coincide with each other and colors are superimposed on one another, a new dot color is formed by subtractive synthesis.

Color rating

A standard measurement system is required to measure, transmit and store color information. Human vision may be considered one of the most accurate measuring instruments, but it is not able to assign specific numerical values ​​to colors, nor remember them exactly. Most people don't realize how significant the impact of color is on their daily lives. When it comes to repetition, a color that appears "red" to one person is perceived as "reddish-orange" to another.

Methods by which objective quantitative characterization of color and color differences are carried out are called colorimetric methods.

The three-color theory of vision allows us to explain the occurrence of sensations of different color hue, lightness and saturation.

Color spaces

Color coordinates
L (Lightness) - color brightness is measured from 0 to 100%,
a - color range on the color wheel from green -120 to red value +120,
b - color range from blue -120 to yellow +120

In 1931, the International Commission on Illumination - CIE (Commission Internationale de L'Eclairage) proposed a mathematically calculated XYZ color space, in which the entire spectrum visible to the human eye lay within. The system of real colors (red, green and blue) was chosen as the base, and the free conversion of some coordinates to others made it possible to carry out various types of measurements.

The disadvantage of the new space was its uneven contrast. Realizing this, scientists carried out further research, and in 1960, McAdam made some additions and changes to the existing color space, calling it UVW (or CIE-60).

Then in 1964, at the suggestion of G. Vyshetsky, the space U*V*W* (CIE-64) was introduced.
Contrary to the expectations of specialists, the proposed system turned out to be insufficiently perfect. In some cases, the formulas used to calculate color coordinates gave satisfactory results (mainly in additive synthesis), while in others (in subtractive synthesis) the errors turned out to be excessive.

This forced the CIE to adopt a new equal-contrast system. In 1976, all differences were resolved and the Luv and Lab spaces were born, based on the same XYZ.

These color spaces are used as the basis for the independent colorimetric systems CIELuv and CIELab. It is believed that the first system is more consistent with the conditions of additive synthesis, and the second - subtractive.

Currently, the CIELab color space (CIE-76) serves as an international standard for working with color. The main advantage of space is independence from both color reproduction devices on monitors and information input and output devices. Using CIE standards, all colors that the human eye perceives can be described.

The amount of color being measured is characterized by three numbers showing the relative amounts of mixed radiation. These numbers are called color coordinates. All colorimetric methods are based on three dimensions i.e. on a kind of volumetricity of color.

These methods provide the same reliable quantitative characteristics of color as, for example, temperature or humidity measurements. The difference is only in the number of characterizing values ​​and their relationship. This relationship of the three basic color coordinates is expressed in a coordinated change when the color of the illumination changes. Therefore, “three-color” measurements are carried out under strictly defined conditions under standardized white lighting.

Thus, color in the colorimetric sense is uniquely determined by the spectral composition of the measured radiation, but the color sensation is not uniquely determined by the spectral composition of the radiation, but depends on the observation conditions and, in particular, on the color of the illumination.

Physiology of retinal receptors

Color perception is related to the function of cone cells in the retina. The pigments contained in cones absorb part of the light falling on them and reflect the rest. If some spectral components of visible light are absorbed better than others, then we perceive this object as colored.

The primary discrimination of colors occurs in the retina; in the rods and cones, light causes a primary irritation, which is converted into electrical impulses for the final formation of the perceived shade in the cerebral cortex.

Unlike rods, which contain rhodopsin, cones contain the protein iodopsin. Iodopsin is the general name for cone visual pigments. There are three types of iodopsin:

• chlorolab (“green”, GCP),
• erythrolab (“red”, RCP) and
• cyanolab (“blue”, BCP).

It is now known that the light-sensitive pigment iodopsin, found in all cones of the eye, includes pigments such as chlorolab and erythrolab. Both of these pigments are sensitive to the entire region of the visible spectrum, however, the first of them has an absorption maximum corresponding to the yellow-green (absorption maximum about 540 nm), and the second yellow-red (orange) (absorption maximum about 570 nm) parts of the spectrum. Noteworthy is the fact that their absorption maxima are located nearby. These do not correspond to the accepted "primary" colors and are not consistent with the basic principles of the three-part model.

The third, hypothetical pigment, sensitive to the violet-blue region of the spectrum, previously called cyanolab, has not been found to date.

In addition, it was not possible to find any difference between the cones in the retina, nor was it possible to prove the presence of only one type of pigment in each cone. Moreover, it was recognized that the cones simultaneously contain the pigments chlorolab and erythrolab.

The non-allelic genes chlorolalab (encoded by the OPN1MW and OPN1MW2 genes) and erythrolab (encoded by the OPN1LW gene) are located on the X chromosomes. These genes have long been well isolated and studied. Therefore, the most common forms of color blindness are deuteronopia (impaired formation of chlorolab) (6% of men suffer from this disease) and protanopia (impaired formation of eritolab) (2% of men). At the same time, some people who have impaired perception of shades of red and green perceive shades of other colors, for example, khaki, better than people with normal color perception.

The cyanolabe gene OPN1SW is located on the seventh chromosome, so tritanopia (an autosomal form of color blindness in which the formation of cyanolabe is impaired) is a rare disease. A person with tritanopia sees everything in green and red colors and cannot distinguish objects in the twilight.

Nonlinear two-component theory of vision

According to another model (nonlinear two-component theory of vision by S. Remenko), the third “hypothetical” pigment cyanolab is not needed, the rod serves as a receiver for the blue part of the spectrum. This is explained by the fact that when the lighting brightness is sufficient to distinguish colors, the maximum spectral sensitivity of the rod (due to the fading of the rhodopsin contained in it) shifts from the green region of the spectrum to the blue. According to this theory, the cone should contain only two pigments with adjacent maximum sensitivity: chlorolab (sensitive to the yellow-green part of the spectrum) and erythrolab (sensitive to the yellow-red part of the spectrum). These two pigments have long been found and carefully studied. In this case, the cone is a nonlinear ratio sensor, providing not only information about the ratio of red and green colors, but also highlighting the level of yellow color in this mixture.

Proof that the receiver of the blue part of the spectrum in the eye is the rod can also be the fact that with color anomaly of the third type (tritanopia), the human eye not only does not perceive the blue part of the spectrum, but also does not distinguish objects in the twilight (night blindness), and this indicates precisely the lack of normal operation of the sticks. Supporters of three-component theories explain why the sticks always stop working at the same time the blue receiver stops working, and the sticks still cannot.

In addition, this mechanism is confirmed by the long-known Purkinje Effect, the essence of which is that at dusk, when the light falls, red colors turn black and white colors appear bluish. Richard Phillips Feynman notes that: “This is explained by the fact that rods see the blue end of the spectrum better than cones, but cones see, for example, dark red, while rods cannot see it at all.”

At night, when the flow of photons is insufficient for the normal functioning of the eye, vision is provided mainly by rods, so at night a person cannot distinguish colors.

To date, it has not yet been possible to come to a consensus on the principle of color perception by the eye.

The light-sensitive apparatus of the eye. A ray of light, passing through the optical media of the eye, penetrates the retina and hits its outer layer (Fig. 51). Here are the receptors of the visual analyzer. These are special light-sensitive cells - sticks And cones(see color table). The sensitivity of the rods is unusually great. They make it possible to see at dusk and even at night, but without distinguishing color, since they are excited by rays of almost the entire visible spectrum. The sensitivity of cones is at least 1000 times less. They become excited only when there is sufficiently strong lighting, but they allow them to distinguish colors.

Due to the low sensitivity of the cones, color discrimination becomes increasingly difficult in the evening and eventually disappears.

In the retina of the human eye, an area of ​​approximately 6-7 sq. cm There are about 7 million cones and about 130 million rods. They are distributed unevenly in the retina. In the center of the retina, just opposite the pupil, there is the so-called yellow spot with a recess in the middle - central fossa. When a person examines a detail of an object, its image falls on the center of the yellow spot. The fovea contains only cones (Fig. 52). Here their diameter is at least half as large as in other parts of the retina, and by 1 sq. mm their number reaches 120-140 thousand, which contributes to a clearer and more distinct vision. As you move away from the central fossa to -. Rods also begin to appear, first in small groups, and then in ever greater numbers, and there are fewer cones. So, already at a distance of 4 mm from the central fossa by 1 sq. mm there are about 6 thousand cones and 120 thousand rods.

Rice. 51< Схема строения сетчатки.

I-.the edge of the choroid adjacent to the retina;

II - layer of pigment cells; III - layer of rods and cones; IV and V are two consecutive rows of nerve cells to which excitation from rods and cones passes;

1 - sticks; 2 - cones; 3 - rod and cone nuclei;

4 - nerve fibers.

Rice. 52. The structure of the retina in the area of ​​the macula (diagram):

/ - central fossa; 2 - cones; 3 - sticks; 4 - layers of nerve cells; 5 - nerve fibers heading to the blind spot,

In semi-darkness, when the cones do not function, a person better distinguishes those objects whose image does not fall on the yellow spot. He will not notice a white object if he directs his gaze at it, since the image will fall on the center of the yellow spot, where there are no rods. However, the object will become visible if you move your gaze to the side by 10-15°. Now the image falls on a region of the retina rich in rods. Hence, with great imagination, one may get the impression of the “ghostliness” of an object, its inexplicable appearance and disappearance. This is the basis for superstitious beliefs about ghosts wandering at night.

In daylight, a person can clearly distinguish the color shades of the object he is looking at. If the image falls on the peripheral areas of the retina, where there are few cones, then color discrimination becomes unclear and rough.

In rods and cones, as in photographic film, chemical reactions occur under the influence of light that act as a stimulus. The resulting impulses come from each point of the retina to certain areas of the visual area of ​​the cerebral cortex.

Color vision. The whole variety of color shades can be obtained by mixing three colors of the spectrum - red, green and violet (or blue). If you spin a disk made up of these colors quickly, it will appear white. It has been proven that the color-sensing apparatus consists of three types of cones:

Some are predominantly sensitive to red rays, others to green, and others to blue. Color vision depends on the ratio of the excitation strength of each type of cone.

Observations of the electrical reactions of the cerebral cortex made it possible to establish that the newborn’s brain reacts

not only for light, but also for color. The ability to distinguish colors was discovered in an infant using the method of conditioned reflexes. The discrimination of colors becomes more and more perfect as new conditioned connections are formed, acquired during the game. ^ Colorblindness. At the end of the 18th century. famous English natural-. tester John Dalton described in detail the color vision disorder from which he himself suffered. He didn't recognize the color red. from green, and dark red seemed gray or black to him. This violation, called colorblindness, occurs in approximately 8% of men and very rarely in women. It is inherited through generations through the female line, in other words, from grandfather to grandson through the mother. There are other color vision disorders, but they are very rare. People suffering from color blindness may not notice their defect for many years. Sometimes a person learns about it during an eye test for a job that requires a clear distinction between red and green colors (for example, as a railway driver).

A child suffering from color blindness can remember that this ball is red and the other, larger one is green. But if you give him two identical balls, differing only in color (red and green), then he will not be able to distinguish them. Such a child confuses colors when picking berries, during drawing classes, or when selecting colored cubes from colored pictures. Seeing this, those around him, including teachers, accuse the child of inattention or deliberateness. pranks, make comments to him, punish him, reduce the grade for the work performed. Such undeserved punishment can only affect the child’s nervous system and affect his further development and behavior. Therefore, in cases where a child is confused or cannot learn certain colors for a long time, he should be shown to a specialist doctor to find out whether this is the result of a congenital vision defect.

Visual acuity. Visual acuity is the ability of the eye to distinguish small details. If rays emanating from two adjacent points excite the same or two adjacent cones, then both points are perceived as one larger one. For their separate vision it is necessary that between;

there was another one with excited cones. Therefore, the maximum possible visual acuity: depends on the thickness of the cones in the central fovea of ​​the macula. It has been calculated that the angle at which rays from two points that are as close as possible, but visible separately, fall on the retina is equal to "/in 0, i.e., one arc minute. This angle is considered to be the norm of visual acuity. Visual acuity varies somewhat depending on the intensity of illumination. -However, even with the same illumination it can vary significantly. It increases under the influence of training if, for example, a person has to deal with the fine distinction of small objects. When tired, visual acuity decreases.

Passion for color

Color perception. Physics

We receive about 80% of all incoming information visually
We understand the world around us 78% through vision, 13% through hearing, 3% through tactile sensations, 3% through smell and 3% through taste buds.
We remember 40% of what we see and only 20% of what we hear*
*Source: R. Bleckwenn & B. Schwarze. Design Tutorial (2004)

Physics of color. We see color only because our eyes are capable of detecting electromagnetic radiation in the optical range. And electromagnetic radiation includes radio waves and gamma radiation and x-rays, terahertz, ultraviolet, infrared.

Color is a qualitative subjective characteristic of electromagnetic radiation in the optical range, determined on the basis of the emerging
physiological visual sensation and depending on a number of physical, physiological and psychological factors.
The perception of color is determined by a person’s individuality, as well as the spectral composition, color and brightness contrast with surrounding light sources,
as well as non-luminous objects. Phenomena such as metamerism, individual hereditary characteristics of the human eye are very important.
(degree of expression of polymorphic visual pigments) and psyche.
In simple terms, color is the sensation that a person receives when light rays enter his eye.
The same light exposure can cause different sensations in different people. And for each of them the color will be different.
It follows that the debate “what color really is” is meaningless, since for each observer the true color is the one that he himself sees

Vision gives us more information about the surrounding reality than other senses: we receive the largest flow of information per unit of time through our eyes.

Rays reflected from objects enter through the pupil onto the retina, which is a transparent spherical screen 0.1 - 0.5 mm thick, onto which the surrounding world is projected. The retina contains 2 types of photosensitive cells: rods and cones.

Color comes from light
To see colors, you need a light source. At dusk the world loses its color. Where there is no light, color cannot arise.

Considering the huge, multimillion-dollar number of colors and their shades, a colorist needs to have deep, comprehensive knowledge about color perception and the origin of color.
All colors represent part of a ray of light - electromagnetic waves emanating from the sun.
These waves are part of the electromagnetic radiation spectrum, which includes gamma radiation, x-rays, ultraviolet radiation, optical radiation (light), infrared radiation, electromagnetic terahertz radiation,
electromagnetic micro- and radio waves. Optical radiation is that part of electromagnetic radiation that our eye sensors can perceive. The brain processes signals received from eye sensors and interprets them into color and shape.

Visible radiation (optical)
Visible, infrared and ultraviolet radiation makes up the so-called optical region of the spectrum in the broad sense of the word.
The identification of such a region is due not only to the proximity of the corresponding parts of the spectrum, but also to the similarity of the instruments used for its study and developed historically mainly in the study of visible light (lenses and mirrors for focusing radiation, prisms, diffraction gratings, interference devices for studying the spectral composition of radiation and etc.).
The frequencies of waves in the optical region of the spectrum are already comparable to the natural frequencies of atoms and molecules, and their lengths are comparable to molecular sizes and intermolecular distances. Thanks to this, phenomena caused by the atomic structure of matter become significant in this area.
For the same reason, along with the wave properties, the quantum properties of light also appear.

The most famous source of optical radiation is the Sun. Its surface (photosphere) is heated to a temperature of 6000 degrees Kelvin and shines with bright white light (the maximum of the continuous spectrum of solar radiation is located in the “green” region of 550 nm, where the maximum sensitivity of the eye is located).
It is precisely because we were born near such a star that this part of the spectrum of electromagnetic radiation is directly perceived by our senses.
Radiation in the optical range occurs, in particular, when bodies are heated (infrared radiation is also called thermal radiation) due to the thermal movement of atoms and molecules.
The more a body is heated, the higher the frequency at which the maximum of its radiation spectrum is located (see: Wien's displacement law). When heated to a certain level, the body begins to glow in the visible range (incandescence), first red, then yellow, and so on. And vice versa, radiation from the optical spectrum has a thermal effect on bodies (see: Bolometry).
Optical radiation can be created and detected in chemical and biological reactions.
One of the most famous chemical reactions, which is a receiver of optical radiation, is used in photography.
The source of energy for most living beings on Earth is photosynthesis - a biological reaction that occurs in plants under the influence of optical radiation from the Sun.

Color plays a huge role in the life of an ordinary person. The life of a colorist is dedicated to color.

It is noticeable that the colors of the spectrum, starting with red and passing through shades opposite, contrasting with red (green, cyan), then turn into violet, again approaching red. This closeness of the visible perception of violet and red colors is due to the fact that the frequencies corresponding to the violet spectrum approach frequencies that are exactly twice as high as the frequencies of red.
But these last indicated frequencies themselves are already outside the visible spectrum, so we do not see the transition from violet back to red, as happens in the color wheel, which includes non-spectral colors, and where there is a transition between red and violet through purple shades.

When a light beam passes through a prism, its components of different wavelengths are refracted at different angles. As a result, we can observe the spectrum of light. This phenomenon is very similar to the rainbow phenomenon.

A distinction must be made between sunlight and light emanating from artificial light sources. Only sunlight can be considered pure light.
All other artificial light sources will affect color perception. For example, incandescent light bulbs produce warm (yellow) light.
Fluorescent lamps most often produce cool (blue) light. To correctly diagnose color, you need daylight or a light source as close to it as possible.
Only sunlight can be considered pure light. All other artificial light sources will affect color perception.

Variety of colors: Color perception is based on the ability to distinguish changes in hue direction, lightness/brightness, and color saturation in the optical range with wavelengths from 750 nm (red) to 400 nm (violet).
By studying the physiology of color perception, we can better understand how color is formed and use this knowledge in practice.

We perceive all the variety of colors only if all cone sensors are present and functioning normally.
We are able to distinguish thousands of different tone directions. The exact amount depends on the ability of the eye sensors to detect and distinguish light waves. These abilities can be developed through training and exercise.
The numbers below sound incredible, but these are the real abilities of a healthy and well-trained eye:
We can distinguish about 200 pure colors. By changing their saturation, we get approximately 500 variations of each color. By changing their lightness, we get another 200 nuances of each variation.
A well-trained human eye can distinguish up to 20 million color nuances!
Color is subjective because we all perceive it differently. Although, as long as our eyes are healthy, these differences are insignificant.

We can distinguish 200 pure colors
By changing the saturation and lightness of these colors, we can distinguish up to 20 million shades!

“You only see what you know. You only know what you see.”
“You only see the driven. You know only what is visible."
Marcel Proust (French novelist), 1871-1922.

The perception of nuances of one color is not the same for different colors. We perceive changes most subtly in the green spectrum - a change in wavelength of just 1 nm is enough for us to see the difference. In the red and blue spectra, a change in wavelength of 3-6 nm is necessary for the difference to become noticeable to the eye. Perhaps the difference in a more subtle perception of the green spectrum was due to the need to distinguish edible from inedible at the time of the origin of our species (Professor, Doctor of Archeology, Hermann Krastel BVA).

The color pictures that appear in our minds are the cooperation of the eye sensors and the brain. We “feel” colors when cone-shaped sensors in the retina of the eye generate signals when exposed to specific wavelengths of light and transmit these signals to the brain. Since color perception involves not only the eye sensors, but also the brain, as a result we not only see color, but also receive a certain emotional response to it.

Our unique color perception in no way changes our emotional response to certain colors, scientists note. No matter what color blue is to a person, they always become a little more calm and relaxed when looking at the sky. Short waves of blue and blue colors calm a person, while long waves (red, orange, yellow), on the contrary, give activity and liveliness to a person.
This system of reaction to colors is inherent in every living organism on Earth - from mammals to single-celled organisms (for example, single-celled organisms “prefer” to process scattered yellow light during the process of photosynthesis). It is believed that this relationship between color and our well-being and mood is determined by the day/night cycle of existence. For example, at dawn, everything is painted in warm and bright colors - orange, yellow - this is a signal to everyone, even the smallest creature, that a new day has begun and it’s time to get down to business. At night and midday, when the flow of life slows down, blue and purple hues dominate around.
In their research, Jay Neitz and his colleagues from the University of Washington noted that changing the color of diffuse light can change the daily cycle of fish, while changing the intensity of this light does not have a decisive effect. This experiment is the basis of scientists' assumption that it is thanks to the dominance of blue color in the night atmosphere (and not just darkness) that living beings feel tired and want to sleep.
But our reactions do not depend on the color-sensitive cells in the retina. In 1998, scientists discovered an entirely separate set of color receptors—melanopsins—in the human eye. These receptors detect the amount of blue and yellow colors in our environment and send this information to areas of the brain responsible for regulating emotions and circadian rhythm. Scientists believe that melanopsins are a very ancient structure that was responsible for assessing the number of flowers back in time immemorial.
“It is thanks to this system that our mood and activity rise when the colors around us are orange, red or yellow,” says Neitz. “But our individual characteristics of perceiving different colors are completely different structures - blue, green and red cones. Therefore, the fact that we have the same emotional and physical reactions to the same colors cannot confirm that all people see colors the same way."
People who, due to some circumstances, have impaired color perception, often cannot see red, yellow or blue, but, nevertheless, their emotional reactions do not differ from the generally accepted ones. For you, the sky is always blue and it always gives a feeling of peace, even if for someone your “blue” is a “red” color.

Three characteristics of color.