"The woman is created for a man, not a man for a woman" - such a postulate ...
Visible light is the energy of that part of the electromagnetic radiation spectrum, which we are able to perceive our eyes, that is, to see. That's so simple.
Wavelength of visible light
And now harder. Light wavelengths in the visible region of the spectrum lie in the range from 380 to 780 nm. What does it mean? This means that the waves are very short and high-frequency, and NM is a nanometer. One such nanometer is 10 -9 meters. And if the human language is one billion part of the meter. That is, the meter is ten decimeters, a hundred centimeters, a thousand millimeters or ... Attention! One billion nanometers.
As we see colors within the visible spectrum of light
Our eyes not only can perceive these tiny waves, but also distinguish their lengths within the spectrum. That's how we see the color - as part of the visible spectrum of light. Red light, one of the three main colors of light, has a wavelength of approximately 650 nm. Green (second main) - approximately 510 nm. And finally, the third is blue - 475 nm (or so). The visible light from the Sun is a kind of cocktail in which these three colors are mixed.
Why the sky is blue, and the grass is green?
Actually, these are two questions, and not one. And so we will give two different, but interconnected answers. We see clear sky At noon blue, because short waves of light are more effectively dissipated when a collision with gas molecules in the atmosphere than long ones. So the blueness, which we see in the sky is blue light, scattered and repeatedly reflected by the atmosphere molecules.
But at sunrise and sunset the sky can acquire a reddish color. Yes, and it happens, believe me. This is because when the sun is close to the horizon, the light to achieve us, you have to do a longer path through a much more dense layer of the atmosphere (moreover, also rather dusty) than when the sun is in the zenith. All short waves are absorbed, and we can be content with long, responsible for the red part of the spectrum.
But with the grass everything is slightly different. It looks green, because it absorbs all wavelengths, except green. Green she, you see, do not like it, so she reflects them back to our eyes. For the same reason, any object has its own color - we see that part of the spectrum of the light that he could not absorb. Black items look black, because they absorb all the wavelengths, almost without reflecting, but white - on the contrary, reflect the entire visible spectrum of light. It also explains why black heats up the sun is much stronger than white.
Blue sky, grass green, dog - friend of man
And what about the visible area of \u200b\u200bthe spectrum?
As the waves become shorter, the color changes from red to blue, reaches purple and, finally, the visible light disappears. But the light itself did not disappear - and moved to the region of the spectrum, which is called ultraviolet. At least we no longer perceive this part of the spectrum of the world, but it is she who makes luminescent lamps, some types of LEDs, as well as all sorts of cool luminous things in the dark. Then the X-ray and gamma radiation are already coming, with which it is better not to have at all.
From the other end of the region of the visible light spectrum, where the red color ends, the infrared radiation begins, which is more heat than the light. It may well fry. Then there is microwave radiation (very dangerous for eggs), and even further - what we used to call radio waves. They are already measured by centimeters, meters and even kilometers.
And how does all this relate to the lighting?
Very related! Since we learned a lot about the spectrum of visible light and about how we perceive it, the manufacturers of lighting equipment are constantly working on improving the quality to meet our every second growing needs. So the lamps of the "full spectrum" appeared, the light of which is almost indistinguishable from natural. The color of light steel to have real numbers for comparison and marketing tricks. Special lamps have become available for various needs: for example, lamps for growing indoor plants, giving more ultraviolet and light from the red region of the spectrum for better growth and flowering, or "thermal lamps" different specieswho settled in domestic heaters, toasteries, and grilled in "Shaurme from Ashot".
In 1676, Sir Isaac Newton with a three-headed prism laid white sunlight On the color spectrum.Various colors are created by light waves, which are a certain genus of electromagnetic energy.
The human eye can only take the light with a wavelength of from 400 to 700 millycron: 1 Millimicron or 1 mt \u003d 1/1 000 000 mm.
The wavelength corresponding to the individual colors of the spectrum, and the corresponding frequencies (the number of oscillations per second) for each prismatic color have its own characteristics.
Each color of the spectrum is characterized by its wavelength, that is, it can be perfectly defined the wavelength or frequency of oscillations. Light waves themselves do not have colors. The color occurs only when the perception of these waves with the human eye and the brain. How it recognizes these waves to date is still not fully known. We only know that different colors arise as a result of quantitative differences in photosensitivity.
It remains to explore the important question about the case color of objects. If we, for example, we put a filter that transmits a red color, and a filter that transmits the green, in front of the arc lamp, then both filters together will give black color or darkness together. The red color absorbs all the rays of the spectrum, except for the rays at that interval that corresponds to the red color, and the green filter delays all the colors other than green. Thus, not a single beam is missing, and we get dark. Absorbed in the physical experiment color are also called deductible.
The color of items occurs mainly in the process of absorbing the waves. Red vessel looks red because it absorbs all other colors of the light beam and reflects only red. When we say: "This cup is red", then we actually mean that the molecular composition of the surface of the cup is such that it absorbs all light rays except red. The cup itself does not have any color, the color is created when it is lighting. If the red paper (the surface absorbing all the rays besides red) is illuminated by green light, the paper will seem black to us, because the green color does not contain rays that respond red, which could be reflected by our paper. All picturesque paints are pigmented or real. This absorbing (absorbing) paints, and when mixed it, should be guided by the deduction rules. When additional paints or combinations containing three main colors are yellow, red and blue are mixed in a certain proportion, the result will be black, while a similar mixture of lovely colors obtained in the Newtonian experiment with prisms gives as a result white colorbecause here the collaboration is based on the principle of addition, and not subtraction.
Two colors whose combination gives white, is called additional colors. If we delete one color from the spectrum, for example, green, and through the lenses we collect the remaining colors - red, orange, yellow, blue and purple, then the mixed color we got red, that is, the color is optional with respect to the green removed. If we remove the yellow color, then the remaining colors are red, orange, green, blue and purple - will give us purple color, that is, the color, extra to yellow. Each color is optional with respect to the mixture of all other spectrum colors. In mixed color, we cannot see the individual components.
Physics color
In 1676, Sir Isaac Newton with the help of a triangled prism laid out white sunlight on the color spectrum. A similar spectrum contained all the colors with the exception of purple.
Newton put his experience as follows (Fig. 1) Sunlight was skipped through a narrow slit and fell on the prism. In the prism, white beam raised on separate spectral colors. It was dismisted in this way, then he was sent to the screen, where the image of the spectrum arose. The continuous color tape began with red and through orange, yellow, green, blue ended with purple. If this image was then skipped through the collecting lens, then the connection of all colors again gave a white color.
These colors are obtained from the solar beam with the help of refraction. There are other physical ways of formation of colors, for example, related to interference, diffraction, polarization and fluorescence processes.
If we divide the spectrum into two parts, for example - on red-orange yellow and green-blue-purple, and we will collect each of these groups with a special lense, then as a result we will get two mixed colors, the mixture of which in turn will also give us white .
Two colors whose combination gives white, is called additional colors.
If we delete one color from the spectrum, for example, green, and by lenses, we collect the remaining colors - red, orange, yellow, blue and purple, then the mixed color we got red, that is, the color is optional with respect to the green removed. If we delete yellow, then the remaining colors - red, orange, green, blue and purple - give us purple color, that is, the color, extra to the yellow.
Each color is optional with respect to the mixture of all other spectrum colors.
In mixed color, we cannot see the individual components. In this regard, the eyes differ from the musical ear, which can allocate any of the sounds of the chord.
Various colors are created by light waves, which are a certain genus of electromagnetic energy.
The human eye can perceive the light only with a wavelength of 400 to 700 millIcron:
- 1 microns or 1μ \u003d 1/1000 mm \u003d 1/1000000 m.
- 1 Millimicron or 1mμ \u003d 1/1000000 mm.
The wavelength corresponding to the individual colors of the spectrum, and the corresponding frequencies (the number of oscillations per second) for each spectral color have the following characteristics:
The ratio of the frequency of red and purple color is approximately 1: 2, that is, the same as in the musical octave.
Each color of the spectrum is characterized by its wavelength, that is, it can be perfectly defined the wavelength or frequency of oscillations. Light waves themselves do not have colors. The color occurs only when the perception of these waves with the human eye and the brain. How it recognizes these waves to the present is still completely unknown. We only know that different colors arise as a result of quantitative differences in photosensitivity.
It remains to explore the important question about the case color of objects. If we, for example, put a filter, transmitting a red color, and a filter that transmits green, in front of the arc lamp, then both filters will give a black color or darkness together. The red color absorbs all the rays of the spectrum, except for the rays at that interval that corresponds to the red color, and the green filter delays all the colors except green. Thus, not a single beam is missing, and we get dark. Absorbed in the physical experiment color are also called deductible.
The color of items occurs mainly in the process of absorbing the waves. Red vessel looks red because it absorbs all other colors of the light beam and reflects only red.
When we say: "This cup is red", then we actually mean that the molecular composition of the surface of the cup is such that it absorbs all light rays except red. The cup itself does not have any color, the color is created when it is lighting.
If the red paper (the surface absorbing all the rays besides red) is illuminated green lightthen the paper will seem black to us because green color Does not contain rays that respond red, which could be reflected by our paper.
All picturesque paints are pigmented or real. This absorbing (absorbing) paints, and when mixed it, should be guided by the deduction rules. When additional paints or combinations containing three main colors are yellow, red and blue, are mixed in a certain proportion, the result will be black, while a similar mixture of lovely colors obtained in the Newtonian experiment with prisms resulting in a white color, Since here the combination of colors is based on the principle of addition, and not subtraction.
1. Light wavelength and color. Color circle. Schedule MKO.
Spectral composition of light
The optical range of the electromagnetic radiation consists of three sections: invisible ultraviolet radiation (wavelength 10-400 nm), visible light radiation (wavelength of 400-750 nm), perceived by the eye as light and invisible infrared radiation (wavelength 740 nm - 1-2 mm).
Light radiation, acting on the eye and causing the feeling of color, are divided into simple (monochromatic) and complex. Radiation with a certain wavelength called monochromatic.
Simple radiations cannot be laid on any other colors.
The spectrum is a sequence of monochromatic radiation, each of which corresponds to a certain wavelength of the electromagnetic oscillation.
With the decomposition of white light, the prism into a continuous spectrum of the color in it gradually passes one to another. It is considered that in some borders of wavelengths (nm) radiation have the following colors:
390-440 - purple
440-480 - blue
480-510 - Blue
510-550 - Green
550-575 - yellow-green
575-585 - Yellow
585-620 - Orange
630-770 - Red
The human eye has the greatest sensitivity to yellow-green radiation with a wavelength of about 555 nm.
Three radiation zones are distinguished: blue-purple (wavelength is 400-500 nm), green (length 500-600 nm) and red (length 600-680 nm). These spectrum zones are also zones of the predominant spectral sensitivity of eye receivers and three layers of color film. The light emitted by conventional sources, as well as the light reflected from the unheoming bodies, always has a complex spectral composition, i.e. - consists of the amount of various monochromatic radiation. The spectral composition of the light is the most important feature of lighting. It directly affects the light when shooting on color photographic materials.
Newton took the first step to the color measurement - systematized color in color tone, building color circle
In addition, Newton conducted experiments by adding different color emissions by introducing concepts basic and additional flowers. He experimentally found that any color can be obtained as the amount of radiation three colors - blue, green and red - named it main colors. This statement was based on the basis of the color equation, where the color is represented by the sum of the emission of three main colors (k, s, c) taken in a certain proportion:
C \u003d kk + zz + ss,
Where s, s, k -the coefficients corresponding to the mixed radiation intensities of blue, green and red. IN foreign literature These intensity values \u200b\u200bare indicated respectively R., G., B..
Color circle - Scheme systematizing color in color tone. In the color spectrum smoothly move one to another, but there are no purple, purple, raspberry tones in the spectrum. In this case, in purple, we obviously feel the presence of red. Therefore, Isaac Newton placed all color Tones As you similar with each other in a circle. Newton has placed color so that each opposite colors lay against each other. In the future, the color circle has somewhat modified
(Color Circle Goethe, color circle of Mansell, etc.), where the condition of the completion of the opposite tones is not respected.
FROM 
the recent stage in the development of colorimetry Polte body of the color coverage of ostelalda was the schedule of MCO (International Commission for Lighting). The need for its creation was caused by the fact that not all saturated colors can be obtained from three main colors. Some colors obtained by the addition of primary colors have less saturation than pure spectral colors. And in order to really any color can be obtained an additive way, the original basic colors must have a saturation of more than 100%, that is, saturated spectral colors. Really such colors can not be, but as mathematical abstractions such colors were introduced. They were calledX, Y, Z - red, green and blue, respectively.
In fact, the MCO graph is a modified color circle on which the colors of 100% saturation are placed. To the center saturation drops to 0. The MCO graph is often used to indicate the color of the radiation various sources Sveta.
In addition to the schedule of MCOs, other colorimetric systems are currently applied, for example Lab. Value L. Determines the brightness of the color, but - the proximity of the color to a red or green color tone, b. - The proximity of the color to blue or yellow.
It should be noted that none of the existing colorimetric systems reflect fully all the phenomena of color vision. Therefore, colorimetric systems continue to develop and improve.
What is color. First of all, it is necessary to determine what color is. For those years that there is a science about the color, there were numerous estimates of the phenomenon of color and color vision, but all of them can be reduced to one simple definition: the color is a set of psycho-physiological human reactions to light radiation, emanating from various self-losing items (light sources) or reflected from the surface of non-simulating items, as well as (in the case of transparent media), passed through them. Thus, a person has the opportunity to see those surrounding it and perceive them with color due to light - concepts physical worldBut the color itself is no longer a concept of physics, as it is a subjective feeling that is born in our consciousness under the action of light.
A very accurate and capacious definition of color was given by Judd and above: ". . . By itself, the color is not reduced to purely physical or purely psychological phenomena. It is the characteristic of light energy (physics) through the vicinity of visual perception (psychology).
From the point of view of physics, the light is one of the types of electromagnetic radiation emitted by glowing bodies, as well as resulting from a row chemical reactions. This electromagnetic radiation has a wave nature, i.e. spreads in space in the form periodic oscillations (waves) performed by him with a certain amplitude and frequency. If you present such a wave in the form of a graph, then it turns out a sinusoid. The distance between two adjacent vertices of this sinusoid is called a wavelength and is measured in nanometers (nm) and is a distance that the light is distributed over a period of one oscillation.
Human eye is able to perceive (see) electromagnetic radiation Only in a narrow range of wavelengths bounded by a section from 380 to 760 nm, which is called a section of visible wavelengths, actually components of the light. We do not see radiation up to 380 and above 760 nm, but they can be perceived by other conname mechanisms (such as infrared radiation) or register with special devices (Fig. 1.1).
Fig. 1.1. Spectrum of electromagnetic radiation and visible light spectrum
Depending on the wavelength, the light radiation is perceived by the human eye painted in a particular color (it is more correct to say, causes a person a feeling of one or another color) from purple to red (Table 1.1). This ability determines the possibility of human color vision.
Spectrum as color characteristic. In nature, radiation from various light sources or items are rarely monochromatic, i.e. represented by the radiation of only one certain wavelength, and has quite complicated spectral composition. It has radiation of a wide variety of wavelengths. If you submit this picture in the form of a graph where the wavelength will be postponed along the ordinate axis, and in the abscissa axis - intensity, then we will obtain addiction called color spectrum of radiation or just a color spectrum. For painted surfaces, the color spectrum is defined as the dependence of the reflection coefficient ρ on the wavelength λ, for transparent materials - the transmission coefficient τ on the wavelength, and for light sources - the radiation intensity from the wavelength. Examples of color spectra of various light sources and materials are shown in Fig. 1.2 and fig. 1.3.
Fig. 1.2. Curves Spectrum of Reflections of various colors: Emerald Green, Red Cynanar, Ultramarine
Fig. 1.3. Examples of spectral distributions of radiation intensities of various light sources: light from a clear blue sky, the average daily sunlight, light incandescent bulbs
On the form of a spectral curve, it is possible to judge the color of radiation reflected from the surface of the subject or emitted by the self-driving light source. The more this curve to a straight line will strive, the more the color of the radiation will seem gray. The smaller or more the amplitude of the spectrum, the color of the emission of the subject will be less or brighter. If the radiation spectrum is zero on the entire range, with the exception of a certain narrow part, we will observe the so-called pure spectral colorcorresponding to monochromatic radiation emitted in a very narrow wavelength range.
As a result of complex processes of interaction of the light flux with the atmosphere surrounding objects and other light fluxes, the energy spectrum of radiation of real objects, as a rule, becomes much more complicated form. In nature, in fact it is impossible to meet clean colors. For example, even if we take the radiation of the Sun at noon for the standard of white, it will actually be not white, but having one or another color that occurs as a consequence of changing the spectral composition solar radiation In the process of its passage through the thickness of the earth's atmosphere: air molecules, as well as in the atmosphere, dust and water particles interact with the stream of solar radiation, and, depending on the wavelength, this process occurs less or more intensively. Therefore, in the evening and morning hours, when the sun is low above the horizon and sun rays Must undergo a greater distance in the atmosphere than at noon, the sunlight seems not white to us, but yellowish, but those who illuminated objects - painted in various shades Yellow, orange, pink and red. This is due to the fact that the atmosphere absorbs short-wave (conditionally blue) and freely passes the long-wave (conditional red) component of the radiation of the Sun. Thus, it turns out that the color of the objects directly depends on the source of the light illuminating the surface of this item. More precisely, the light radiation reflected from the surface of the subject or the sensation of this object in the visual apparatus in the visual apparatus is defined as the properties of the item itself reflect either absorb light depending on the wavelength and the properties of the light source used to illuminate this item, Change the radiation intensity depending on the wavelength (Fig. 1.4). Therefore, when conducting color dimensions, it is necessary to always take into account the lighting used at the same time and, if possible, use only standard light sources, and not use several different type sources at once. The same applies to any work with color images when it is necessary to ensure the high accuracy of color reproduction.The phenomenon of color vision. When carrying out his famous experience on the decomposition of sunlight in the Newton's spectrum made a very important observation: despite the fact that the spectral colors smoothly moved into each other, running the whole mass of all sorts of color shades, in fact, all this variety of colors was possible to reduce seven colors that They were named primary: red, yellow, orange, yellow, green, blue, blue, and purple. Subsequently, various researchers showed that the number of these colors can be reduced to three, namely to red, green and blue. Indeed, yellow and orange there is a combination of green and red, blue - green and blue. The same applies to all other color tones that can be obtained by a combination of red, green and blue colors, so main colors.
Jung and Hemgolts, engaged in color vision studies, suggested that such phenomena are explained by the presence of three color sensitive analyzers in the apparatus of human vision, each of which is responsible for the perception of red, green and blue light emissions entering the eye. Later, this assumption received sufficiently good scientific confirmations and formed the basis of a three-component theory of color vision, which explains the phenomenon of the color vision by the existence of three types of color-carrying cells, sensitive to the light of various spectral composition.
These cells really managed to see in the retina of the eye and since under the microscope they appeared in the form of rounded oblongable bodies several incorrect formThey were called Kolzkov. Columns are divided into three types depending on whether they are sensitive to the radiation of which spectral composition, and are designated by the Greek letters β (beta), γ (gamma) and ρ (RO). The first type (β) has a maximum sensitivity to light waves with a length of 400 to 500 nm (the conditionally "blue" component of the spectrum), the second (γ) - to light waves from 500 to 600 nm (the conditionally "green" component of the spectrum) and the third (ρ) - to light waves from 600 to 700 nm (conventionally "red" component of the spectrum) (Fig. 1.5 b). Depending on light waves What length and intensity are present in the spectrum of light, those or other groups of colums are stronger or weaker.
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but) |
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b) |
Fig. 1.5. The curve of the relative light efficiency of the sticks (dotted line) and colums (A) and the curves of the spectral sensitivity of the colums normalized to one (b)
The presence of other cells was established that do not have sensitivity to strictly defined spectral radiations and react to the entire flow of light radiation. Since these cells are visible under the microscope as elongated bodies, they were called them with chopsticks.
In an adult, there are about 110-125 million sticks and about 6-7 million columns (1:18 ratio). Conditionally speaking, we see the image, as well as the image is digital, discretely. But since the number of image elements is very large, we just do not feel it.
It is interesting to note another feature. The light sensitivity of the sticks is much higher than the sensitivity of the colodes and therefore at twilight or at night, when the intensity of the radiation falling into the eye becomes very low, the columns cease to work and the person sees only by sticking. Therefore, at this time of the day, as well as in low light conditions, a person ceases to distinguish between colors and the world appears in front of it in black and white (dusk) tones. Moreover, the light sensitivity of the human eye is so high that much exceeds the possibilities of most existing image registration systems. The human eye is able to react to the flow of light radiation about 10 -16 W / cm. If we wanted to use this energy to heat the water, in order to heat one cubic centimeter of water for 1 °, it would be required to 1 million years old. If you express the sensitivity of the human eye in the units of the sensitivity of the film, it will be equivalent to a photofill with a sensitivity of 15 million ASA units.
The sensitivity of sticks and colodes to the light stream depending on the wavelength is described by the curves of the spectral sensitivity of the human eye (Fig. 1.5 b). To characterize the total spectral sensitivity of the human eye to the flow of light radiation, the relative curve of light efficiency is used, or, as it is also called, the curve of visidity, the eyes, which defines the overall sensitivity of the human eye to the light, taking into account the color (columin) or the light (wand) of view ( Fig. 1.5 a). These addicts are of great interest to specialists, since they allow us to explain a number of well-known phenomena of human vision.
So, according to these curves, you can see that a person is very well able to perceive green and green-yellow colors, while its sensitivity to blue colors is noticeably lower.
The situation varies somewhat in twilight, when the wizards sensitive to the bright light radiation begin to lose their effectiveness and the ratio between sticks and kolloches changes - the maximum spectral light efficiency is shifted towards blue emissions (sticky vision).
Other interesting feature It is that the eye lens is harder to focus on objects if they are painted in blue-purple tones. This is due to the drop in the spectral sensitivity of the eye in these spectrum areas. Therefore, the glasses are sometimes done not neutral-transparent, but from painted in yellow or brown glass, which filter the blue-purple component of the spectrum.
Due to the fact that the curves of spectral sensitivity partially overlap, the person can face certain difficulties in distinguishing certain clean colors. So, due to the fact that the curve of the spectral sensitivity of the rolling of type R (conditionally sensitive to the red part of the spectrum) retains some sensitivity in the field of blue-violet colors, it seems to us that blue and purple colors have a mixture of red.
Affects the perception of color and the total light sensitivity of the eye. Since the relative light efficiency curve is a Gaussian with a maximum at a point of 550 nm (for day vision), then colors on the edges of the spectrum (blue and red) are perceived by us less bright than colors occupying the central position in the spectrum (green, yellow, blue) .
Since the spectral sensitivity of the human eye is uneven across the entire spectrum area, phenomena may occur when two different colors that have different spectral distributions will seem equal to us the same due to the fact that they cause the same excitement of eye receptors. Such colors are called metaalog, and the described phenomenon - metallic. It is often observed when the one or another painted surface is considered by us with different sources of lighting, the light of which interacting with the surface changes the spectrum of its color. In this case, for example, a white cloth may look white in daylight, and with artificial lighting it is changed its shade. Either two subjects having different reflection spectra, and, accordingly, which must have different color, are actually perceived by us as the same, since they cause unambiguous excitation of three color-carrying eye centers. Moreover, if we try to reproduce the color of these items, let's say, on a film that uses the image that is different from the visual apparatus, the image registration mechanism, these two subjects will most likely have a different color.
Fig. 1.6. Illustration of the phenomenon of metamery
Three color samples having different spectral reflection coefficients seem to illuminate them daylight same. When reproducing these samples on a film, the spectral sensitivity of which is different from the spectral sensitivity of the human visual apparatus, or when the lighting changes, they change their color and become diodranous.
On the use of the metamer's phenomenon, the entire modern technology of color image reproduction is based: without having the ability to repeat the range of one or another color observed in the color reproduction. natural conditionsIt is replaced with color synthesized using a certain set of paints or emitters and having an excellent spectral distribution, but causing the audience the same color sensations.
Knowledge of the characteristics of human vision is very important when designing and image processing systems design. It is in order to maximize the degree of human view features, the manufacturers of photographic materials add additional flower sensitive layers, manufacturers of printers - additional printed paints, etc. However, no improvements modern technologies Nevertheless, do not allow the image of the image reproduction system that could be compared with the Human Vision Apparatus.
Classification of colors. As already mentioned, depending on the length of the radiation wavelength, the light is perceived by the human eye painted in one or another color from purple to red. The colors perceived at the same time call pure spectral colorsAnd the characteristic defining their color is called colorimetry with color tone. The color tone is uniquely connected with the wavelength and therefore is often expressed in nanometers.
It is believed that the human eye is able to distinguish to 150 different color tones of pure spectral colors. To this number, another 30 purple colors should be added, which are not in the spectrum, but can be obtained by mixing the blue and red spectral radiation.
In addition to pure spectral and pure purple flowers, there are also a number of colors called achromatic or neutral flowers, i.e., the colors devoid of color. This includes black, white and lying between them various shades of gray. The feeling of these colors occurs when the flow of light radiation (black) is not valid for the human eye or vice versa, the flow of maximum intensity (white color) is valid. The feeling of gray arises when the light stream acts on the eye excites the flower sensitive analyzers (columns) equally. Moreover, the emission spectrum of this color does not necessarily be uniform (equivalentergic), it is sufficient only so that it causes the same excitation of three color-carrying choppers, and the emission spectrum itself can be very uneven (Fig. 1.6).
If you mix pure spectral color with white or gray, there will be a phenomenon when the color starts to lose its purity and gradually move into white or grey colour. In this regard, a characteristic, called saturation, or purity of color, is also used to characterize the color in addition to color tones. In fact, clean spectral colors in nature can be found not so much, and instead we are much more often observed in one degree or another devoid of saturation. It is believed that for each color tone, the human eye is able to distinguish to 200 steps of saturation.
The characteristics of the color tone and saturation are often combined together and are called chroma, which can serve qualitative characteristic Color perception.
Two identical color tones may differ from each other not only by saturation, but also the brightness (strength) of their radiation, which, when characterizing the properties of non-simulating objects, it is customary to characterize the concept of light color. If color saturation can be interpreted as a ratio of pure and added to it white, the light drive can be interpreted as a ratio of pure color and added to it of black. As the strength (brightness) of the light radiation increases, the color takes various color shades from black to white. SPLOTTERT is directly related to color saturation, since the change in color brightness often leads to a change in its saturation.
If chromaticity can be used as a quality color characteristic, the SFLOT can be used as a quantitative color rating.
Three color characteristics considered by us, namely the color tone, saturation and lightness, often position in the form of a three-dimensional graph on which the value of the light vehicle serves as a reference axle, along which colors are located from black to white, saturation varies through the radial coordinate as color from the color of the graph removes and the color tone is characterized by the angular coordinate, as shown in Fig. 1.7. Theoretically, such a schedule should be a cylinder, but it is often positioned in the form of an inverted cone, the vertex of which corresponds to the point of black, and the base is the maximum value of the lightness. This is well consistent with the fact that with small values \u200b\u200bof the brightness of the radiation, the person begins to distinguish the colors worse, and with the minimum brightness value does not distinguishes them at all.If you use to draw this schedule on the plane to remove the coordinate of the lightweight and leaving only the color tone or color tone and saturation (chromaticity), we will get the construction that is customized to call the color circle (Fig. 1.8), which is a circle along which color tones are located from red to purple. Each color in the color circle has a numerical coordinate, expressed in degrees from 0 ° to 360 °. The red color begins and closes the color circle, corresponding to the point 0 ° (360 °). Orange corresponds to 40 ° coordinate, yellow - 60 °, green - 120 °, blue - 180 °, blue - 240 °, purple - 300 °. All these colors, with the exception of orange, which is a mixture of red and yellow, turns out to be located on a color circle at an equal range from each other 60 °.
Fig. 1.8. Color circle
Colors in color circle each opposite each other are called additional colors. For example, red and blue, green and purple, blue and yellow, etc. These color pairs have a number of interesting properties that are used in the image playback technology and which will be described in detail below.
The characteristics of the color tone, saturation and lightness are most used visual either, as they are also called psychophysical Color characteristics and are used when the color must be determined without resorting to a complex mathematical apparatus.
Other color definition means can serve as colors atlas in which samples of flowers are given on different surfaces and materials grouped by a specific feature. Such atlases are widely used in printing, textile industry and architecture. For example, Pantone printed colors, samples of building koles, etc. Each color in the colors of the atlas has its own index by which its position in the atlas can be determined, as well as the formulation of the paints necessary for its receipt.
Colorimetry is widely used by the Color Atlas of Mansell, compiled in the early 20th century by the American artist Albert Mansell. Mansell grouped colors in three coordinates color Tone (Hue.), saturation (Chroma.) I. lights (Value.).
Mansell divided the color tones (HUES) on 10 main tones, which he identified by the corresponding letter indexes: R. (red), Yr. (yellow-red), Y. (yellow), GY. (yellow-green), G. (green), BG. (blue-green), B. (blue), PB. (Purple blue) and RP. (red-purple). In each of them he allocated 10 shades, thus obtaining 100 pure color tones. He placed them in a circle, creating a geometric construction similar to the color circle already known to us. The values \u200b\u200bof the tones were chosen by Mansell so that the samples adjacent to each other had the same color difference to the eye of the ordinary observer when normal conditions Lighting (under such lighting Mansell understood the midwood light of the sky in the northern latitudes). Using the center of the resulting circle as a point of achromatic colors, Mansell has placed color samples from the center of the circumference to its edge in accordance with the increasing saturation (chroma) of colors. Finally, from the center of the circle, he built the axis along which the colors were grouped as their lights increase (Value). According to the degree of increasing the colors, the colors were divided into 10 groups from 0 (black) to 9 (white), and the brightness scale was not chosen not linear, but the logarithmic, which more corresponds to how the change in the brightness is perceived by a person. But according to the degree of increasing saturation of the color did not have a clear and equal separation, since the spectral sensitivity of the human eye in different areas The spectrum is not the same, and therefore saturation differences for different colorsthings man can see less or more accurately. So for 5Y. with Value \u003d. 2 Mansell allocated 3 degrees of saturation, and for 5pb. With the same light - 28 . At the same time different values Lights The possible number of color samples having a different saturation was also unequal, which is consistent with the fact that a person is not able to distinguish between the colors with too low and too high brightness. If grouped the color samples into the spatial body, the geometric construction thus obtained will be somewhat asymmetric, reminding a little apple slightly incorrect shape or a deformed ball. By the way, it is thus in the form of a peculiar color globe of the Color Atlas Mansell often also appeared to the consumer (Fig. 1.10).For an accurate task of this or that color Mansell used a special coordinate system, which is indicated by HUE (color tone), Value (Svetlota) / Chroma (saturation). For example, a red-purple color is indicated in the atlas as 6RP4 / 8.where 6RP - Color coordinate having light weight 4 With satiety 8 .
In addition to Mansell, a number of other researchers were engaged in the development of such color atlases. In Germany, a similar color atlas, and almost at the same time as Mansell, developed an ostel. Similar works were taken in Canada, USA and a number of other countries, and several national color standards were often created at once for different areas Industry. In the Soviet Union, the Color Atlas of Rabkina and Atlas Vniimi was developed and used. D. I. Mendeleev.
In addition to color atlases, numerous color classification systems for their name were also developed. Although these systems can not be called to the end scientifically reliable (under the same name different observers may understand different colors), but as a supplement to the existing classification systems, they can serve a good service.
As the simplest example, the seven names of the colors describing the sections of the visible spectrum and the components in the entire well-known formula about the hunter and the pheasant are: red, orange, yellow, green, blue, blue, purple.
The terms that are accustomed to operate artists are already very more complex and, naturally, numerous. If we take the sets of paints sold in stores for artists, you will find among the names of the paints, such as oche, cobalt, kinovar, etc., which are generally accepted terms, which from any professional artist will be associated with certain colors, although, of course which colors implies under one or another name special person There will be inevitably differences.
Numerous attempts to develop more stringent in the scientific relationship of color naming systems have been taken. So Martz and Paul created a color dictionary containing almost 4,000 titles, of which about 36 are represented by their own names, 300 are complex words consisting of the name of the color and the appropriate adjective. In 1931, the Interdepartmental Committee on the Color (ISCC) of the United States commissioned by the Pharmacological Committee developed a system of named colors to describe the color of painted surfaces. This system covered 319 designations based on the names of the colors proposed by Mansell. This included the names of the main tones - "Red" (R), "Yellow" (Y), "Green" (G), "Blue" (B)"Purple" (P), Olive (OL), "Brown" (BR) and "pink" (PK)- To which adjectives "weak", "strong", "light", "dark", and the terms "pale", "brilliant", "deep", "twilight", "Live" were added to designate additional colors.
All other systems developed by other researchers are built in a similar way and usually numbered up to several hundred names. As an example of such a system widely used in Internet applications, you can bring a system of 216 colors recommended by the W3C Internet Consortium (World Wide Web Consortium) as standard colors that can be used to specify the color within the HTML language.
Characteristics of light sources. Since radiation from the objects around us and the materials falling into our eyes and causing the feeling of color, which is determined among the variety of light radiation, which is able to perceive the human eye, highlight radiation, actually emitted by one or another self-driving source, such as the sun, incandescent lamp , photographic flash lamp, etc. Since light sources play a very important role in determining the color of items and materials, they were studied in detail and a special system of their classification was developed, which is based on the concept color temperature.
As you know, if you heat the metal item to a high temperature, it will begin to emit light radiation. The higher the temperature temperature, the more intense it will be this glow. At the same time, depending on the temperature temperature, its color will also change. At first it will be dark red, then red, then orange, then white. As it turns out, this phenomenon is characteristic not only by the metal, but is observed when he heated many solid tel With high melting point. It is on its use that electric incandescent lamps built: thin tungsten wire is skipped electricityAs a result, the wire heats up and empties light. Moreover, the color of the object of the object can be quite accurately appreciated depending on the temperature of the tungsten of the tungsten: when heated to a temperature of several hundred degrees, it has a reddish tint, when heated to 1000K - orange, 2000K - yellow; The glow of the body heated to several thousand degrees is perceived by us as white. The light of the sun is also due to the radiation arising from the reactions flowing on its surface heated to a temperature of about 6500k. The surface of some stars has a temperature of over 10000K and therefore the color of their radiation is blue (Table 1.5). As the temperature changes, the spectral composition of the radiation is also varied accordingly (Fig. 1.11).
Fig. 1.11. Normal spectral distributions of absolutely black bodies radiation at different color temperatures
Since the nature of radiation for most self-losing sources is subject to the same laws, it was proposed to use the temperature as a characteristic of the color of the radiation. Since for different tel depending on their chemical composition And the physical properties of heating to a given temperature gives a slightly different radiation spectrum, a hypothetical absolutely black body is used as a standard temperature reference temperature, which is a complete emitter, the radiation of which depends only on its temperature and does not depend on any other properties.
The spectrum of the glow of absolutely black body depending on the temperature of its heating can be determined by the law of the plank. Despite the existing differences, all other bodies behave in heating quite similar to the perfect black body and therefore the use of color temperature as the characteristics of the chromaticity of the emissions of the self-driving sources, both natural and artificial, turns out to be justified for a very large number of cases. Since the spectral distribution of radiation, and, accordingly, its chromaticity given by the real body rarely, when exactly coincides with the spectral distribution and the chromaticity of the perfect black body at a given color temperature, the concept of actually existing bodies use the concept correlated color temperature, which means that color temperature of the perfect black body, in which the chromaticity of its radiation coincides with the color of the emission of this body. At the same time, the spectral composition of the radiation and the physical temperature of these bodies are usually different, which is quite logical from the difference physical properties Real and perfect black bodies.
Accordingly, how much there exists in the world of light sources operated when different conditionsSo much exists and the spectral distributions of their radiation. So the phases of sunlight and their correlated color temperatures varies in very wide limits, depending on the geographical position, time of day and state of the atmosphere (Fig. 1.12, Table 1.6). The same applies to artificial light sources, such as incandescent lamps, whose color temperature varies depending on their design, operating voltage and operation mode (Table 1.6).
Fig. 1.12. Normated spectral distributions of various phases of daylight: 1) The light of the sky in the zenith, 2) the light of the sky is completely covered with clouds 3) direct sunlight at noon; 4) direct sunlight in 1 hour before
However, despite the existing diversity of various light sources, most of the light sources used in industry and technology can be standardized. Such standardization was proposed by the International Commission on Illumination (MCO), in accordance with which several so-called standard colorimetric emitters were allocated, which were marked with Latin letters. A., B., C., D., E. and F. (Table 1.7). In contrast to real light sources, standard MFA emitters describe the classes of light sources in general, based on the averaged values \u200b\u200bof their spectral distributions. Such standardization has shown its sufficient efficiency, since, as it turns out, despite the differences, most of the real light sources can be quite accurately compared with the corresponding standard emitters.
Table. 1.7.
Standard Colorimeter Emitters MKO
| Art. gentle Chatel |
Characteristic |
| A. | Under this source, MCO lacked the full light emitter (perfect black body) at 2856k. To play it uses the incandescent lamp with a tungsten thread with a correlated color temperature of 2856k, and for more accurate playback of the entire source spectrum, and it is recommended to use paws with a melted quartz flask |
| B, C. | Reproduce daylight sunlight: B. - direct sunlight with correlated color temperature 4870K, C. - Indirect sunlight with correlated color temperature 6770k. When calculating these emitters, a number of inaccuracies were allowed and therefore, they are practically not used in colorimetric calculations by replacing the standard emitter D.. For this reason, in the Specification of Standard Emitters, MCOs are often not specified at all. |
| D. | It is a standard light source, which is calibrated by most image equipment. Reproduces various phases of the average daily light in the range of correlated color temperatures from 4000K to 7500K. Radiation spectral distribution data D. It was determined by averaging the data of numerous dimensions of the daylight spectrum performed in various areas of Great Britain, Canada and the United States. For various purposes, several spectral source distributions were defined D. For different color temperature values: D50, D55, D60, D65., D70, D75. With correlated color temperatures, respectively, 5000K, 5500K, 6000K, 6500K, 7000K, 7500K, corresponding to certain phases of daylight. A source D65. It should be considered the most versatile, since it most accurate approximates the average daily light. A source D50 Accepted as standard in printing, since it is best for the characteristics of the image printed by standard typographic paints on paper. A source D55 Accepted as standard in the photo: It is the lamps with a color temperature of 5500K are used in viewing equipment for slides and this color temperature has light flashlights. Unlike other standard sources, accurately reproduce standard sources D. It is quite difficult, since artificial light sources with such spectral radiation distribution does not exist. As the most used solutions that satisfy the consumer, both qualitatively and economically, can be called the use of luminescent lamps with an appropriate correlated color temperature, the radiation spectrum is additionally adjusted using special light filters. |
| E. | A hypothetical radiation source having an equivalent energy (non-changeable with a change in wavelength) spectrum with color temperature 5460K. Really does not exist in nature and is used in colorimetry in only calculated purposes |
| F. | Standard emitter describing the spectral distribution of radiation of various fluorescent lamps. F1. - radiation of a warm luminescent lamp with a correlated color temperature 3000K, F2. - a luminescent lamp of cold daylight with a correlated color temperature of 4230K, F7. - fluorescent daylight lamp with correlated color temperatures 6500K |
Along with the color temperature, its reverse value, called mirth, is sometimes used (denotes μRD) or reverse microelvin.
The use of μRD instead of the Kelvin scale has two advantages: firstly one unit μRD approximately corresponds to a single threshold of the color of the color of the light flux and therefore it is more convenient to characterize the color of radiation in these units; Secondly, μRD is convenient to use for the characteristics of color conversion and color-balanceing light filters: a change in the color temperature provided by the filter, expressed in μRD will not change when working with radiation from one color temperature to another
For example, an orange conversion filter of the 85th series lowers the color temperature of the midday color from 5500K to 3400K at 2100K (112 μRD). However, if it is used to reduce the color temperature of the light flux with a color temperature of 4000K, the color temperature change is expressed in K will not be 2100K, but 7246k, but not changed in μRD.
Addition of colors. Getting a new color by mixing several basic colors determines the ability to receive color images in photography, cinema, television, printing and computer technology. It is based on the phenomenon of the mixing of the emission spectra formed by the painted surfaces or light emitters. As a result, a new color is obtained having its own spectrum (Fig. 1.13).
If, for example, take three light emitters equipped with red, green and blue light filters and spread their radiation at one point on the white screen, then we will get white spot. If one of the emitters turn off and mix only the radiation of the red emitter with green, blue with green and green with red, on the screen we get the first yellow, then purple and then blue. If you take all the three emitters and mix their radiation in a different proportion, then we can thus get pretty big number Colors and their shades. The less the difference in the intensity of the three emitters, the less the color is saturated and the more he will strive for neutral. If not changing the proportions of the three radiation to reduce their intensity, then we will get the same color but having a smaller brightness. In the limiting case, when the intensity of all three emitters is reduced to zero, we will get black.
For the case when only two main colors are taken:
In fact, instead of red, green and blue, we could take any color, but simply by mixing red, green and blue, you can get the largest combination of colors. The obvious explanation of this fact is the features of human vision and the presence of three color-carrying receptors in the visual apparatus, each of which is sensitive to red, green and blue rays. Thus, the formation of color with the help of three emitters of blue, green and red flowers can be considered as directed excitation of three color receptors of the eye, as a result of which it turns out the possibility of calling the viewer with a feeling of one or another color.
According to a similar scheme, the formation of a color image on the screen of the video and computer monitor, TV, the LCD projector and in other devices that are used to synthesize the color of three main colors or (for image entry devices) decompose the image on the main colors.
Since to obtain the color of the emission of the three main colors (fold), this method of coloring attachment received the name of the additive (from the verb add. - fold).
Fig. 1.13. Adducive mixing of flowers
The drawing illustrates the preparation of an additive color mixture on the example of the Sony Trinitron color monitor. Radiation from three phosphors of red (R), green (G) and blue flowers (B)The spectral radiation of which is shown in the figure, are summed up for each wavelength, which makes it possible to obtain a color mixture reproducing depending on the intensity of the luminescence of each phosphor a large number of different colors and their shades. Note that the glow of the red phosphor has an almost scheduled spectrum, which is due to the presence in its composition of rare-earth elements
In most cases, however, to fold the light streams of three emitters for formation of color is not technologically possible, for example, in cinema, photographs, printing, textile and paint industry.
In the photo, the luminous flux of white light passes through the three colorful layers of a photo material formed by yellow, purple and blue dye. In printing, the light stream passes through a layer of yellow, purple and blue paint and reflecting from the surface of the paper passes in the opposite direction, forming a color image.
As a result of the passage of the light flux of white light through a layer of dye or pigment, the selective absorption of the energy of the radiation spectrum occurs, as a result of which the light stream acquires one or another color.
Thus, it turns out possible using yellow, purple and blue dyes, illuminated with light white light as a color radiation modulator, obtaining all the same streams of red, green and blue radiation, with which you can control the excitation of three color-carrying eye centers.
Fig. 1.14. Spendtractive mixing of flowers
Figure illustrates the receipt of a subtractive color mixture on the example of the color handling film by successive absorption blue (C)Purple (M) and yellow (Y) dyes with densities C \u003d 100%, m \u003d 60%, y \u003d 20% radiation from the light source of daylight (D65) In each wavelength interval. The color obtained as a result of their mixing is one of the shades of blue. The radiation obtained as a result of partial absorption of the luminous flux by subtractive dyes may in this case are considered as a product of the radiation spectrum of the light source and the dye reflection spectra
In print and printing to three yellow, purple and blue paints, black is still added. It is dictated, firstly, economic considerations, since it allows to reduce the flow rate of more expensive color paints, and secondly, it allows you to solve some fundamental problems arising in the process of tricolor typographical printing as a result of the imperfection of the printed paints used, the spectrum of reflection of which in practice is not limited only to yellow , only purple and only blue.
Since, to obtain color, light fluxes are not folded, and the light flux of white light is partially absorbed as a result of interaction with the dye, such a method of color attachment received the name of the subtractive (from the verb subtract - deduct).
