Municipal budgetary educational institution gymnasium
Test
Presentation on theme: "Color Perception"
Kharitonov Lev
Introduction
What is color
Color perception
Range. Basic types of color
Conclusions and conclusion
Literature
Introduction
Light gives us the opportunity to see and study everything around us on earth, as well as much that is outside the earth in boundless outer space. We perceive light with the help of the organ of vision - the eye. At the same time, we feel not only light, but also color. We not only see illuminated or luminous objects around us, but we can also judge their color. The property of the eye - not only to see the objects and phenomena around us, but also to feel their color - gives us the opportunity to observe the inexhaustible richness of the colors of nature and reproduce the colors we need in different areas of life and activity.
The purpose of our work is to study what color is, how it is formed and where it is applied.
To achieve this goal, we have set the following tasks:
According to literary sources and materials on the Internet, get acquainted with the definition of the concept of color, types of color, features of color perception by the eye and mechanisms for obtaining a color image.
Conduct experiments various methods composition of flowers.
Consider the use of color in various areas of our lives
The following research methods were used in the work:
analysis of literary sources;
experiment;
photography and video recording.
1. What is color
Color - characteristic of visible light, range electromagnetic waves.
Color can be associated with the spectral characteristics of light rays having a certain wavelength. The action of light on the photoreceptors of the eye determines the nature of the sensation of color. Light is one form of energy. Sources of light - various bodies emitting light rays. Other bodies only reflect light. It is thanks to this that we see them (in absolute darkness, bodies do not reflect light, and we do not see anything).
Light is made up of rays of different colors. You can verify this by passing sunlight through a prism. Isaac Newton conducted an experiment on the decomposition of sunlight (Fig. 1). He used to decompose the light small piece glass in the form of a trihedral prism. When the sun's rays pass through the raindrops, each droplet works like a prism and a rainbow appears. The color of objects depends on what color rays they absorb and reflect. Color characteristics and features are related to the physical properties of the object, material, light sources, etc., such as, for example: absorption, reflection, or emission spectra.
color spectral light
Rice. 1. Scheme of the decomposition of a white light beam into a spectrum using a glass prism.
Glass transmits all visible rays. White material reflects all visible rays. The black material absorbs all rays. Green leaf absorbs red rays, reflects green. Red material reflects red rays, others absorb.
Color perception
Color is one of the properties of the objects of the material world, perceived as a conscious visual sensation. This or that color is “assigned” by a person to objects in the process of their visual perception.
In the vast majority of cases, the color sensation occurs as a result of exposure to eye flows. electromagnetic radiation from the wavelength range in which this radiation is perceived by the eye (visible range - wavelengths from 380 to 760 nm). Sometimes a color sensation occurs without exposure to the radiant flux on the eye - with pressure on eyeball, shock, electrical stimulation, etc., as well as by mental association with other sensations - sound, heat, etc., and as a result of the work of the imagination. Various color sensations are caused by differently colored objects, their differently illuminated areas, as well as light sources and the lighting they create. In this case, the perception of colors may differ (even with the same relative spectral composition of the radiation fluxes) depending on whether the radiation enters the eye from light sources or from non-luminous objects. In human language, however, the same terms are used for the color of these two different types objects. The main proportion of objects that cause color sensations are non-luminous bodies that only reflect or transmit light emitted by sources. In the general case, the color of an object is due to the following factors: its color and the properties of its surface; optical properties of light sources and the medium through which light propagates; properties of the visual analyzer and features of the still insufficiently studied psychophysiological process of processing visual impressions in the brain centers.
Currently, color perception is associated with the three-component hypothesis of vision. It is based on the assumption that the retina (organism, eye) should contain three types of photoreceptors (called cone cells) with different absorption spectra, for example, the absorption of "red" light rays, where, for example, cones are more sensitive to red light rays. respond more actively. Similarly, it happens with the interactions of other cones that are more sensitive to other primary colors (for example, blue, green). There are suggestions that the number of such types of photoreceptors may be more than three. However, to date, there is no confirmation of these hypotheses.
Range. Basic types of color
Remember one of the most beautiful natural phenomena - a rainbow. The rain has not completely passed, the rays of the sun break through the clouds, and a huge multi-colored rainbow appears in the sky, the colors of which smoothly turn into one another.
Looking at the rainbow, it is impossible to indicate the boundaries of individual colors; only a few characteristic areas are named, located in the following order from top to bottom: red, orange, yellow, yellow-green, green, blue, indigo and purple. In reality, each of the specified color areas of the rainbow, in turn, consists of many color shades, smoothly turning one into another. The properties of our eye are such that within each color area we distinguish only a limited number of colors from each other. Newton gave an explanation for the appearance of the rainbow. The rays of the sun are refracted in raindrops, as in prisms, and white light is decomposed into its component parts. As a result, we see a rainbow, consisting of many spectral colors, passing one into another.
The rainbow is the spectrum of sunlight. If we passed the light of an ordinary electric incandescent lamp through a trihedral prism, we would be convinced that the spectrum of the incandescent lamp is similar to the spectrum sun rays. All incandescent bodies give a spectrum of the same kind. The transition from one color to another occurs continuously, therefore such a spectrum is called continuous. The entire spectrum can be divided into two parts according to color shades. One part includes red, orange, yellow and yellow-green colors, and the other part includes purple, blue, blue and green colors. The colors of the first part of the spectrum are associated with the idea of the color of incandescent bodies - fire, therefore they are called warm colors. And the colors of the second part of the spectrum are associated with the color of water, ice, metal and are called cold colors.
Primary and secondary colors.
The concept of "additional color" was introduced by analogy with the "primary color". It has been found that optical mixing of certain pairs of colors can give the impression of white. So, to the triad of primary colors Red - Green - Blue, additional colors are Cyan - Purple - Yellow - colors. On the color wheel, these colors are placed in opposition, so that the colors of both triads alternate. In printing practice, different sets of "primary colors" are used as primary colors.
Primary and secondary colors.
This division is based on a synthesis of the ideas of many scientists (Lomonosov, Jung, Helmholtz, Goering). The primary colors include the “primary colors”, the secondary ones refer to all the others that can be obtained by mixing the primary ones.
Chromatic and achromatic colors.
All colors found in nature are divided into achromatic and chromatic. Achromatic colors include white and black, as well as gray, which is intermediate between white and black. All gray colors can be obtained by mixing black and white flowers taken in different proportions. For example, if you mix soot with chalk in different proportions, you get black gray colors of different lightness. Achromatic colors are absent in the spectrum - they are colorless. There are countless colors in nature. However, the human eye is able to distinguish only a limited number of them - about 300 achromatic colors from white to black.
Chromatic colors are all colors that have a particular color shade. These include, for example, all spectral colors (green, yellow, red, etc.)
What determines the color of objects
What determines the color of objects around us? Which physical meaning corresponds to our idea that the grass is green, the sky is blue, the paint is red, etc.?
Let a luminous flux of a light source with a continuous or line spectrum fall on some translucent body. Part of this light flux will be reflected from the surface of the body, part of it will pass through the body, and part will be absorbed by it. The ratio of the light fluxes reflected and transmitted by the body to the incident light flux is called the total, or total, reflection and transmission coefficients and is expressed as a percentage. So, for example, freshly fallen snow has a reflection coefficient of 85, white paper, 75, black leather - 1 - 2%. This means that snow reflects 85, white paper 75, and black leather reflects 1 - 2% of the light flux falling on them.
Surfaces that do not change the spectral composition of the light falling on them and have a reflection coefficient of at least 85% are called white (snow). The bodies or media through which the light flux passes without changing its spectral composition are called colorless. For example, transparent window glass.
Surface covered with red paint illuminated with white sunlight, appears red to us. If we look through a blue light filter (blue glass) at the luminous filament of an incandescent lamp, the latter appears to us of blue color. This means that the surface covered with paint, we therefore see red, because it reflects the red, orange and yellow rays well and badly all the rest. Looking through a blue light filter at the luminous filament of an incandescent lamp, we see the latter as blue because the blue light filter from the totality of the rays of an incandescent lamp transmits only blue, violet and blue rays, which as a result give us the sensation of blue.
Bodies and media that unequally reflect or transmit light of different wavelengths, when illuminated with white light, have one or another color corresponding to their physical properties, and are called colored.
Thus, the color of the objects surrounding us depends, firstly, on their ability to reflect or transmit the light flux falling on them and, secondly, on the distribution of the light flux in the spectrum of the light source illuminating them.
When we say that a surface has a green color (when illuminated with white light), this means that of the entire set of rays that make up white light, this surface reflects predominantly green rays. The rays reflected by the surface act on our eye, and we get the sensation of green. The medium (glass, liquid), which appears to us colored green (when illuminated with white light), transmits predominantly green rays from the entire set of rays that make up white light.
The color of objects that we see also depends on the brightness of the color.
Let's do an experiment. Let a sheet of paper, painted in any color, be illuminated by direct sunlight. Cover with some white opaque object half a sheet of paper from direct sunlight. One part of the sheet will be shaded, and its brightness will be less than the second part of it. And although both halves of a sheet of paper, shaded and unshaded, equally reflect light, i.e. qualitatively the same, but their color is different. The difference is that the brightness of both parts of the paper is not the same.
So, pink at low brightness will appear to us as burgundy, yellow - brown, and blue - blue. The brightness of a color is its quantitative parameter.
Mixing colors and color image
Spectral colors are the purest colors that we have to observe, since they do not contain white impurities. However, they do not exhaust the variety of colors that exists in nature. A complete set of naturally occurring colors can be obtained by mixing spectral colors with each other in various proportions, as well as by mixing spectral colors with achromatic ones - white and black.
Mixing colors is understood as the phenomenon of the formation of new colors by composing them from two or more other colors.
Numerous experiments have established that some pairs of chromatic colors, mixed in a certain proportion, form an achromatic color. Two colors that form an achromatic color when mixed are called complementary. In nature, there are countless pairs of complementary colors, including spectral ones. Such colors are, for example, red and cyan, blue and yellow, green and magenta. If one of the two complementary colors is warm, then the other is cold. This is completely understandable, since in the composition of warm colors there are almost no blue and blue radiations, and in cold colors there are almost no red and orange radiations. In white, there are both warm and cold colors.
Additive color addition.
Additive color mixing is a color synthesis method based on the addition of additive colors, that is, the colors of directly emitting objects. The method is based on the structural features of the human visual analyzer, in particular on such a phenomenon as metamerism.
By mixing the three primary colors - red, green and blue - in a certain ratio, most of the colors perceived by humans can be reproduced.
One example of the use of additive synthesis is a computer monitor whose color image is based on the RGB color space and is made up of red, green, and blue dots.
Rice. 2. Additive (a) and subtractive (b) color addition
In contrast to additive color mixing, there are subtractive synthesis schemes. In this case, the color is formed by subtracting certain colors from the light reflected from the paper (or passing through the transparent medium). The most common subtractive synthesis model is CMYK, which is widely used in printing.
The subtractive way of forming colors is widely used in color cinema and color photography. Subtractive color formation occurs when paints are applied to the surface of paper, canvas or other materials. Paint is grains of one or more different pigments mixed together and held together by some kind of binder. The binder may be colorless and transparent, or have selective transmission and some scattering.
Experience in additive mixing of colors when reflecting light is as follows. Two disks of different colors, cut along the radius, are inserted one into the other so that a disk consisting of two sectors is obtained. different colors(Fig. 3). By pushing one disk onto another, you can change the ratio of the areas of the sectors of the taken colors.
Rice. 3. Sliding discs for color mixing during rotation
When the disks are rapidly rotated around their centers with the help of a small electric motor, we do not distinguish the colored sectors that make up this circle separately. Color sectors quickly follow one after another, and create in the eye the sensation of one mixed color. By changing the ratio of multi-colored sectors, you can get all kinds of mixtures, intermediate between the colors taken.
Thus, by mixing the primary colors with a small electric motor, many different intermediate shades can be obtained.
Similarly, by additively adding the primary colors (red, green and blue), an image is also obtained on the computer monitor screen, mobile phone etc. We made sure of this by examining the image on the screen of a mobile phone under a microscope (Fig. 4). As you can see in the figure, it is built from the smallest rectangles - pixels that glow in red, blue and green.
Rice. 4. A fragment of the image on the screen of a mobile phone under a microscope
When paint is applied to a sheet of white paper, the colors are different, since in this case there is a subtractive mixing of colors.
Conclusions and conclusion
Based on the results of the work, we can draw the following conclusions:
Color is one of the properties of the objects of the material world, perceived as a conscious visual sensation. This or that color is “assigned” by a person to objects in the process of their visual perception. Color perception depends on many factors.
The color of objects is due to the impact on our eye of rays of a certain spectrum (green, red, etc.) reflected by the object.
As a result of our experiments, we found out how additive and subtractive color addition occurs and how a color image is obtained on a luminous screen.
In the presented work, not all aspects of such an interesting and multifaceted phenomenon in our life as color are considered. A detailed study of all the characteristics of color, its meaning in nature and practical application in human life is engaged in a special area of science - color science. The significance of this work lies in understanding the general essence of color and performing some experiments on the formation, mixing and decomposition of colors. The prospect of work may be the study of the influence of color on the psychological and functional state of the human body and the development on this basis of the school's own project, the details of which have not yet been disclosed.
Literature
1. Ashkenazi G.I. Color in nature and technology - 4th ed., Revised. and additional - M.: Energoatomizdat, 1985. - 96 p., ill.
2. Bukvareva E.N., Chudinova E.V. Natural science. 3rd grade, 2000.
Tutoring
Need help learning a topic?
Our experts will advise or provide tutoring services on topics of interest to you.
Submit an application indicating the topic right now to find out about the possibility of obtaining a consultation.
Of absolutely exceptional importance in human life is the organ of vision, which allows you to clearly and fully know about all the objects surrounding the body. Through we receive 90% of all information entering the brain. It is no coincidence that the role of vision in our work is so huge.
The eye is often likened to a camera. Indeed, there is a considerable resemblance here. The eye also consists, firstly, of a lens, that is, a series of refractive lenses that collect light rays at one point and make it possible to place an image of huge objects on small areas of the retina. Secondly, the eye is equipped with the actual photosensitive - special substances that can chemically change under the influence of light and thereby send signals to the brain. These substances are placed in specially arranged retinas, called rods and cones after their shape. Cones are located only in the center of the retina and cause color vision. Light fluctuations different frequency, i.e., different wavelengths, affect the substances of cones in different ways, which is why perception occurs different colors. Rods are scattered throughout the retina and are sensitive only to white light, but to a much greater extent than cones to individual colors of the spectrum. Therefore, at dusk, when the perception of colors is no longer there, we still distinguish the outlines of objects, but only, so to speak, in black and white. They all appear to be the same gray. The substance that breaks down in rods under the influence of light and that sends signals to the brain is the so-called visual purple,. Nature made vitamin A an integral part of it. Therefore, night vision suffers without this vitamin. Decaying in the light, rhodopsin is restored in the dark. The more it is in the reduced state, the more sensitive the eye is to light. Therefore, having been in the dark for some time, thanks to the restoration of a significant part of rhodopsin, we begin to distinguish objects that were previously absolutely indistinguishable. Such an adaptation of the eye to the conditions of illumination also refers to the phenomena of adaptation. After an hour of being in the dark, adaptation increases the light sensitivity of the eye by 200,000 times. And how often do we think about this wonderful property of our eyes! We also add that the electrical signal that occurs during the decay of rhodopsin in the rods, the nerve cells of the retina connected to them, is amplified a million times, only then is energy obtained that is capable of giving a nerve impulse that rushes to the brain.
If you take a rabbit and, after keeping it for 3-4 hours in the dark (to restore all the visual purple), show it an illuminated object for a moment, and then, again in the dark, remove the eye and act on it with alum that stops the further decay of rhodopsin, you can such a retina to see the image of the shown object. Where the light has acted and the purple has disintegrated, the retina will be pale, in other places it will be pink. It is clear that if the rabbit manages to look at several objects, the experiment will fail.
Let us now return to the first part of the eye - the lenses that collect light rays into a narrow beam with a focus on the retina. The main lens is the lens. When we look at a distant object, from which rays are almost parallel, the lens becomes flatter. Divergent rays come from a nearby object, which must be refracted to a greater extent in order to give focus at the same point. Therefore, when viewing a close object, the lens becomes more convex. These changes in the lens are called accommodation. They are controlled by the higher parts of the brain. In some people, the lens refracts too much and the focus is not on the retina, but in front of it. When it comes to close objects, which require a strong refraction of the rays coming from them, this does not interfere with vision. Distant objects appear blurry because their image on the retina is out of focus. Such people are called nearsighted. They reduce the excessive bulge of their lens due to biconcave lenses - glasses.
There is also an opposite situation. The fact is that with age the lens loses its ability to accommodate, that is, it becomes more convex if necessary. For the myopic, in whom it is already too convex, it does not matter: they remain myopic all their lives. With normal vision, the ability to see small objects close up decreases with age. In such cases, they speak of farsightedness and correct it with glasses with biconvex lenses. It is clear that in the distance these people see no better than. in youth, but at least not much worse. Only in this sense can they be called far-sighted.
color perception(color sensitivity, color perception) - the ability of vision to perceive and convert light radiation of a certain spectral composition into a sensation of various color shades and tones, forming a holistic subjective sensation (“chroma”, “color”, color).
Color is characterized by three qualities:
- color tone, which is the main feature 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 notices color changes only when the so-called color threshold (the minimum color change visible 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 a complex radiation that consists of simple color components - monochromatic (single-color) radiation. The colors of monochromatic radiation are called spectral.
If a white beam is decomposed into a spectrum using a prism, then a series of continuously changing colors can be seen: 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.
Various objects a person sees colored in different colors because monochromatic radiations are reflected from them in different ways, in different proportions.
All colors are divided into achromatic and chromatic
- Achromatic (colorless) are gray colors of various lightness, white and black colors. 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 that enters the eye of the observer, but also on psychological features 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 (the unit of brightness is candela per meter, cd / m).
Saturation subjectively characterizes the intensity of sensation of a color tone.
Since not only the source of radiation and the colored object, but also the eye and brain of the observer are involved in the appearance of the visual sensation of color, some basic information about the physical nature of the process should be considered. color vision.
Eye color perception
It is known that the eye is similar to a camera in which the retina plays the role of a light-sensitive layer. Emissions of different spectral composition are recorded by retinal nerve cells (receptors).
The receptors that provide color vision are divided into three types. Each type of receptor absorbs the radiation of the three main zones of the spectrum - blue, green and red in a different way, i.e. has different spectral sensitivity. If blue zone radiation enters the retina of the eye, then it will be perceived by only one type of receptors, which will transmit information about the power of this radiation to the brain of the observer. The result is a sensation of blue. The process will proceed similarly in the case of exposure to the retina of the radiation of the green and red zones of the spectrum. With simultaneous excitation of receptors of two or three types, a color sensation will occur, depending on the ratio of the radiation powers of different zones of the spectrum.
With simultaneous excitation of receptors that detect radiation, for example, the blue and green zones of the spectrum, a light sensation can occur, from dark blue to yellow-green. The sensation of more blue shades of color will occur in the case of a higher power of the blue zone radiation, and green shades - in the case of a higher power of the green zone of the spectrum. The equal power of the radiation of the blue and green zones will cause a sensation blue color, green and red zones - the sensation of yellow, red and blue zones - the sensation of magenta. Cyan, magenta, and yellow are therefore called dual-zone colors. Equal in power radiation of all three zones of the spectrum cause a feeling of gray color of different lightness, which turns into white color with sufficient radiation power.
Additive Light Synthesis
This is the process of obtaining different colors by mixing (adding) the radiation of the three main zones of the spectrum - blue, green and red.
These colors are called the primary or primary radiations of adaptive synthesis.
Various colors can be obtained in this way, for example, on a white screen using three projectors with blue (Blue), green (Green) and red (Red) color filters. On screen areas illuminated simultaneously from different projectors, any colors can be obtained. The change in color is achieved in this case by changing the ratio of the power of the main radiations. The addition of radiation occurs outside the eye of the observer. This is one of the varieties 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 elements of the image. Such, for example, as raster dots. But at the same time, small elements of the image move along the retina of the eye, so the same receptors are consistently 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 the mixture.
Subtractive color synthesis
This is the process of obtaining colors by absorbing (subtracting) radiation from white.
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 paint absorbs (subtracts from white) red radiation, magenta - green, and yellow - blue.
In order to obtain, for example, red color in a subtractive way, you need to place yellow and magenta filters in the path of white radiation. They will absorb (subtract) respectively blue and green radiation. The same result will be obtained if white paper apply yellow and purple paint. Then only red radiation will reach the white paper, which is reflected from it and enters the eye of the observer.
- The primary 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.
Additional colors are the colors of two radiations or two colors, which in the mixture make an achromatic color: W + C, P + W, G + K.
In additive synthesis, complementary colors give gray and white colors, since in total they represent the radiation of the entire visible part of the spectrum, and with subtractive synthesis, a mixture of these colors gives gray and black colors, in the form of the fact that 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 printing color images, the so-called process printing inks are used: cyan, magenta and yellow. These colors are transparent and each of them, as already mentioned, subtracts the radiation of one of the spectral bands.
However, due to the imperfection of the components of subactive 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 you can get all the primary (primary) colors for both additive and subtractive synthesis. This circumstance proves the possibility of obtaining colors of the required characteristics in the manufacture of color printing products with process inks.
The color reproduction characteristics change differently depending on the printing method. In gravure printing, the transition from light areas of the image to dark areas is carried out by changing the thickness of the ink layer, which allows you to adjust the main 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 areas. Here, the characteristics of the reproduced color are regulated by the sizes of raster elements of different colors. It was already noted earlier that colors in this case are formed by additive synthesis - spatial mixing of colors of small elements. However, where raster dots of different colors coincide with each other and paints are superimposed on one another, a new color of the dots is formed by subtractive synthesis.
Color Rating
To measure, transmit and store color information, you need standard system measurements. human vision may be considered one of the most accurate measuring instruments, but it is not able to assign certain numerical values to colors, nor to remember them exactly. Most people don't realize how significant the impact of color is in their daily lives. When it comes to repeated reproduction, a color that appears "red" to one person is perceived as "reddish-orange" by others.
The methods by which an objective quantitative characterization of color and color differences is carried out are called colorimetric methods.
The three-color theory of vision allows us to explain the appearance of sensations of different color tone, 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 +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 color space XYZ, in which the entire spectrum visible to the human eye lay inside. The system of real colors (red, green and blue) was chosen as the base, and the free conversion of some coordinates into others made it possible to carry out various kinds of measurements.
The disadvantage of the new space was its uneven contrast. Realizing this, scientists conducted 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 experts, the proposed system was not perfect enough. In some cases, the formulas used in the calculation of color coordinates gave satisfactory results (mainly with additive synthesis), in others (with subtractive synthesis), the errors turned out to be excessive.
This forced the CIE to adopt a new equal contrast system. In 1976, all disagreements were eliminated and the spaces Luv and Lab were born, based on the same XYZ.
These color spaces are taken as the basis for independent colorimetric systems CIELuv and CIELab. It is believed that the first system meets the conditions of additive synthesis to a greater extent, and the second - subtractive.
Currently, the CIELab color space (CIE-76) serves as the international standard for working with color. The main advantage of space is independence both from color reproduction devices on monitors and from information input and output devices. With CIE standards, all colors that the human eye perceives can be described.
The amount of measured color 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 volumetric color.
These methods provide equally reliable quantitative characteristic colors, such as measuring temperature or humidity. The difference is only in the number of characterizing values and their relationship. This interrelationship of the three primary color coordinates results in a consistent change as the color of the illumination changes. Therefore, "tricolor" measurements are carried out under strictly defined conditions under standardized white illumination.
Thus, the color in the colorimetric sense is uniquely determined by the spectral composition of the measured radiation, while 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.
Primary color discrimination occurs in the retina; in rods and cones, light causes primary irritation, which turns into electrical impulses for the final formation of the perceived hue in the cerebral cortex.
Unlike rods, which contain rhodopsin, cones contain the protein iodopsin. Iodopsin - common name 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 of about 540 nm.), And the second yellow-red (orange) (absorption maximum of about 570 nm.) parts of the spectrum. Attention is drawn to the fact that their absorption maxima are located nearby. This does not correspond to the accepted "primary" colors and is not consistent with the basic principles of the three-component 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, and it was not possible to prove the presence of only one type of pigment in each cone. Moreover, it was recognized that the pigments chlorolab and erythrolab are simultaneously present in the cone.
The non-allelic genes for chlorolab (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 (a violation of the formation of chlorolab) (6% of men suffer from this disease) and protanopia (a violation of the formation of erytolab) (2% of men). At the same time, some people who have impaired perception of shades of red and green, better people with normal color perception perceive shades of other colors, such as khaki.
The cyanolalab OPN1SW gene is located on the seventh chromosome, so tritanopia (an autosomal form of color blindness in which the formation of cyanolalab is impaired) - rare disease. A person with tritanopia sees everything in green and red colors and does not distinguish objects at dusk.
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 illumination 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 blue. According to this theory, the cone should contain only two pigments with adjacent sensitivity maxima: chlorolab (sensitive to the yellow-green region of the spectrum) and erythrolab (sensitive to the yellow-red part of the spectrum). These two pigments have long been found and carefully studied. At the same time, the cone is a non-linear ratio sensor that provides not only information about the ratio of red and Green colour, but also separating the level yellow color in this mixture.
Proof that the receiver of the blue part of the spectrum in the eye is a rod can also be the fact that with a 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 at dusk (night blindness), and this points to the absence normal operation sticks. Proponents of three-component theories explain why always, at the same time as the blue receiver stops working, the sticks still cannot work.
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 whites appear bluish. Richard Phillips Feynman notes that: "This is because the rods see the blue end of the spectrum better than the cones, but the cones see, for example, dark red, while the rods cannot see it at all."
At night, when the photon flux 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.
"Color is what you see, not what you might see"
Ralph M. Ivens
“Color is never alone, it is always perceived in the environment of other colors”
Johannes Itten
The division of the problem of color into physical, psychophysical and psychological aspects is not an artificial technique. The emission of visible light, the evaluation of color by a standard observer under standard conditions, and the perception of color that occurs individually and in real conditions, these are three separate phenomena, each of which obeys its own laws and has its own specific differences. Under no circumstances should they be mixed.
The perception and discrimination of colors by each person is determined by the mutual influence physiological processes and cultural traditions in which this person grew up depends on the system of naming colors in his native language and individual characteristics individual. Seeing color in specific conditions is a combination of attention, focus, memory and motives of the individual. The average observer will say that the leaf is green, even if the light reaching his eyes is blue. He may not notice it. An artist who looks through green foliage will say that the distant view is pinkish: he was looking at the color, and his adaptation to the foliage caused the pinkish color of the distant fog. Everyone is right in their own way and everyone is entitled to their opinion.
The perception of colors changes with age, depends on visual acuity, on the nationality of a person, even on the color of his hair and on what he ate (after eating, the sensitivity of the eye to the short-wave (blue part of the spectrum) increases. True, such differences relate mainly to subtle shades colors, so with some assumption we can say that most people perceive primary colors in the same way (except, of course, color blind people).
Dean Judd calculated that under sufficiently large variations in the conditions of observation, the number of perceived colors reaches 10 million. But this is not all. The difference in physical qualities - the properties of a surface or material can be an obstacle to recognizing their identity. The image of the world around us is caused by endless variations in color and shape, created by many types and qualities of objects in different types of lighting. In addition, the perception of color also depends on the conditions of observation: color adaptation, the background against which a given color is viewed, a person's mood, color preferences, etc.
There are concepts of isolated and non-isolated perceived color (Fig. 12).
Fig 12. Isolated color and non-isolated perceived colors
The difference between them is that isolated is the color of a surface or colored light observed in a completely black environment, non-isolated is a color visible against a background that differs from black. In the first case, the observer evaluates the color based entirely on visual information from the eyes (there is no context), in the second, when a white background is introduced around the compared colors, which carries information about the source, it allows the observer to evaluate its brightness and color. In this case, the colors are no longer isolated. They are exposed to neighboring colors and the light source.
Color is a three-dimensional quantity and is used to characterize each of the three dimensions. subjective color characteristics(Fig. 13 ) :
· lightness(refers to non-luminous objects) - color characteristic, according to which the surface is perceived as diffusely reflecting or transmitting a greater or lesser proportion of the incident light;
· Color tone- a color characteristic that serves to establish the similarity of a given color with one or another spectral or purple color, is determined by the name red, blue, green, etc.
· saturation- a color characteristic that serves to assess the difference between a given color and an achromatic color equal to it in lightness.
Rice. 13 An illustration of a change in one of three color characteristics: lightness, hue, and saturation.
The sensation of color depends to some extent on all its characteristics, so everything color parameters should be analyzed in close relationship. Saturation and lightness of non-luminous objects are interrelated, since an increase in selective spectral absorption with an increase in the amount (concentration) of the dye is always accompanied by a decrease in the intensity of reflected light, which causes a feeling of a decrease in lightness. Thus, a rose with a richer purple color is perceived as darker. , than a rose with the same but less pronounced color tone.
It is necessary to dwell in detail on the laws of perception of light and color, as they play great value in color design.
Laws of perception of light and color(Weber-Fechner law, adaptation, constancy, contrast) are due to the fact that all human analyzers (including the eyes), with the help of which the energy of an adequate stimulus is transformed into the process of nervous excitation and, ultimately, leads to the formation of sensation, have a number of psychophysiological or psychophysical properties. These properties are discussed in detail:
1. Extremely high sensitivity to adequate stimuli. The quantitative measure of sensitivity is threshold intensity, that is, the lowest intensity of the stimulus, the impact of which gives a sensation. The lower the threshold intensity, or, simply threshold, the higher the sensitivity.
2. Differential or contrast sensitivity. All analyzers have the ability to establish a difference in intensity between stimuli. The main thing is the presence of a quantitative relationship between the intensity of sensation and the intensity of the stimulus. In a series of experiments (1830–1834), E. Weber showed that it is perceived not an absolute, but a relative increase in the strength of the stimulus (light, sound, load pressing on the skin, etc.), that is, DI/I = const. The visible threshold is a constant part of the stimulus. If the intensity of the stimulus increases, the threshold increases. Based on these observations, G. Fechner in 1860 formulated the “basic psychophysical law”, according to which the intensity of our sensations L proportional to the logarithm of the intensity of the stimulus I : L = k log I/I 0 , where I 0 - boundary value of the intensity of the stimulus. Weber-Fechner law when describing the perception of light brightness, it is observed in a small range of brightness and determines the relationship between lightness and brightness in the most favorable observation conditions. If, for example, the sharpness of the border between the compared sections is reduced, the threshold will increase. It is known that at twilight, when the illumination is low, the brightness of objects differs worse than at medium illumination, and the threshold, consequently, also increases. In conditions of too high brightness, objects have a blinding effect on the eye, and the threshold increases again. For luminances that are at the edges of the perceived luminance range, the threshold is much larger. The contrast sensitivity of the eye has a maximum at the adaptation brightness.
Light-sensitive apparatus of the eye. A beam of light, passing through the optical media of the eye, penetrates the retina and enters its outer layer (Fig. 51). Here are the receptors of the visual analyzer. These are special cells that are sensitive to light. sticks and cones(see color table). The sensitivity of the sticks is unusually great. They make it possible to see at dusk and even at night, but without color discrimination, as they are excited by rays of almost the entire visible spectrum. The sensitivity of cones is at least 1000 times less. They come into a state of excitement only with sufficiently strong light, but they allow you to distinguish colors.
Due to the low sensitivity of the cones, color discrimination becomes more and more difficult in the evening and eventually disappears.
in the retina human eye on 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, is the so-called yellow spot with a hole in the middle central fossa. When a person examines a detail of an object, its image falls on the center yellow spot. There are only cones in the central fossa (Fig. 52). Here their diameter is at least half that in other parts of the retina, and 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 meet, first in small groups, and then in increasing numbers, and the cones become smaller. 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 - two consecutive rows nerve cells, to which excitation passes from rods and cones;
1 - sticks; 2 - cones; 3 - nuclei of rods and cones;
4 - nerve fibres.
Rice. 52. The structure of the retina in the macula (scheme):
/ - central fossa; 2 - cones; 3 - sticks; 4 - layers of nerve cells; 5 - nerve fibers heading to the blind spot,
In the 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 shift your gaze to the side by 10-15 °. The image now hits an area of the retina rich in rods. Hence, with great imagination, the impression of a “ghostly” object, its inexplicable appearance and disappearance, may arise. This is the basis of superstitious ideas about ghosts wandering at night.
In daylight, a person clearly distinguishes 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 indistinct and rough.
In rods and cones, as well as on photographic film, under the influence of light, chemical reactions acting as an irritant. The resulting impulses come from each point of the retina to certain areas of the visual cortex hemispheres.
Color vision. The whole variety of color shades can be obtained by mixing the three colors of the spectrum - red, green and purple (or blue). If you quickly rotate a disk made up of these colors, 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 brain of a newborn reacts
not only for light, but also for color. The ability to distinguish colors was found in baby method conditioned reflexes. Distinguishing colors becomes more and more perfect as new conditional connections are formed, acquired during the game. ^ Daltonism. At the end of the XVIII century. famous English nature-. tester John Dalton described in detail a color vision disorder from which he himself suffered. He did not distinguish red. from green, and dark red seemed to him gray or black. This violation, called colorblindness, occurs in about 8% of men and is very rare in women. It is inherited through the generation 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. Those suffering from color blindness may not notice their defect for many years. Sometimes a person learns about it during an eye test for admission to a job that requires a clear distinction between red and green colors (for example, a machinist on a railway transport).
A child who is colorblind may remember that this balloon is red and the other, larger one, is green. But if you give him two identical balls that differ only in color (red and green), then he will not be able to distinguish them. Such a child confuses colors when picking berries, in drawing classes, when selecting colored cubes from colored pictures. Seeing this, others, including educators, accuse the child of inattention, or deliberate. pranks, make comments to him, punish him, lower the mark for the work done. Such an undeserved punishment can only be reflected in nervous system child, affect him further development and behavior. Therefore, in cases where a child confuses or cannot learn certain colors for a long time, he should be shown to a specialist doctor to find out if this is the result. birth defect vision.
Visual acuity. Visual acuity is the ability of the eye to distinguish the smallest details. If the rays emanating from two nearby points excite one and the same or two neighboring cones, then both points are perceived as one larger one. For their separate vision, it is necessary that between;
excited cones was another. Therefore, the maximum possible visual acuity: depends on the thickness of the cones in the fovea macula. It is calculated that the angle at which the rays fall on the retina from two points as close as possible, but visible separately, is equal to "/ in 0, i.e. one arc minute. This angle is considered to be the norm of visual acuity. Visual acuity changes somewhat depending on the strength of the 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 fine discrimination of small objects.When fatigued, visual acuity decreases.
