First article
In daily life, when people observe colors, they often associate colors with specific things. What people see is not only the colored light itself, but the unity of light and objects. When color is associated with specific things and perceived by people, it is influenced by psychological factors (such as memory and contrast). ) to a large extent, it forms a psychological color. In order to describe color qualitatively and quantitatively, there are three characteristics that distinguish psychological color, namely hue, lightness and saturation. The three basic characteristics of psychological color, also known as psychological three attributes, can roughly correspond to the three variables of colorimetry-dominant wavelength, brightness and purity. Tone corresponds to the main wavelength, lightness corresponds to brightness and saturation corresponds to purity. This is the corresponding relationship between the psychological feeling of color and the physical stimulation of color light. Each specific color has these three characteristics at the same time.
Hue refers to the basic appearance of color, which is the most important and basic feature to distinguish colors. It represents the difference in color quality. Understanding hue from the perspective of physical stimulation of light refers to the different color representations of light with different wavelengths after mixing. Understanding hue from the perspective of human color perception physiology refers to different color feelings produced by different stimuli of three color perception cones. Therefore, hue represents the psychological reaction of different colors caused by light stimulation of different wavelengths. For example, red, green, yellow and blue are all different shades. However, due to the different experience of observers, there will be different color vision. However, every observer almost always divides the spectrum into red, orange, yellow, green, cyan, blue, purple and many intermediate colors in wavelength order. Red generally refers to more than 6 10nm, yellow is 570-600 nm, green is 500-570 nm, cyan and blue are below 500nm, purple is about 420nm, and the rest are colors in between. So the hue depends on the spectral components that stimulate the human eye. For monochromatic light, the hue depends on the wavelength of monochromatic light; For polychromatic light, the hue is determined by the ratio of each wavelength of polychromatic light. As shown in Figure 5- 1, different wavelengths of light give people different color perception. Therefore, the wavelengths of different colors of light can be used to express the appearance of colors, which is called the main wavelength. Such as red (700 nm) and yellow (580 nm).
The correspondence between hue and dominant wavelength will change with the change of light intensity, as shown in Figure 5-2, in which the dominant wavelength of color shifts with the change of light intensity. Only the three main wavelengths of yellow (572nm), green (503nm) and blue (478nm) are constant, which is called constant color point. Hue is usually the color under normal light.
Under normal circumstances, the human eye can distinguish more than 150 hues in the spectrum, plus more than 30 magenta colors outside the spectrum, * * * is about 180. For the convenience of application, the basic order of hue is red, orange, yellow, green, cyan, blue and purple.
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The second article
Why do human eyes feel color?
Author: Anonymous repost from: unknown
When you walk into the bustling department store, red, green, blue and white clothes, green apples, golden oranges, and bright commodities and trademarks in the window will come into your eyes. Color is too closely related to human beings. In this colorful world, the human eye can distinguish at least thousands of colors.
What does color feel like in the eyes? In the long process of understanding color vision, British physicist Newton made a pioneering contribution. He first proved that color is not the objective property of light, but the subjective feeling after different wavelengths of light stimulate the eyes through the famous prism spectroscopy experiment. Unfortunately, for a long time after Newton's thought was put forward, people's research only stayed on the description of color vision phenomenon. /kloc-in the 0/8th century, it is generally believed that there are three primary colors: red, green and blue, and all other colors are mixed by the three primary colors in different ways.
1802, Thomas Young, a British physicist, kicked off the systematic study of color vision. In an article about the wave theory of light, he proposed for the first time that the three primary colors are not the physical characteristics of light, but are determined by the mechanism that the eyes are sensitive to colors. He assumed that there were three kinds of oscillators in the eyes, which could respond to red light, green light and blue light respectively. In 1867, German physicist Herman Ludwig Helmholtz supplemented this, and made a more accurate description: There may be three mechanisms in the human retina that are sensitive to red, green and blue light respectively, and these three mechanisms emit different signals under the stimulation of rice with different wavelengths, which are transmitted to the brain and produce feelings of various colors. This theory is the first in modern color vision research and has far-reaching influence. This is Yang Yi-Helm Holtz's tricolor theory.
The trichromatic light theory makes some important color vision phenomena scientifically explained. For example, any color can be mixed with red, green and blue. However, in the face of other color vision phenomena, trichromatic light theory can do nothing. For example, why doesn't a color look like red and green? Why does a gray area look red when surrounded by a bright green ring? In this case, other color vision theories came into being. The most important one is the antagonistic color theory put forward by German psychophysicist Ewald Hering in 1878. This theory assumes that there are six independent primary colors: red, yellow, green, blue, white and black. These six primary colors form three pairs: red and green, yellow and blue, black and white. Because they are not compatible with each other in perception, there is no green red or blue yellow, which Hering calls antagonistic color. Hailing believes that it is these antagonistic mechanisms that form the basis of color vision. Antagonistic color theory explains some color perception phenomena that trichromatic theory can't explain.
For more than a century, both of these theories have adopted a stricter narrative method in the fierce debate, and at the same time, they have continuously promoted the study of color width.
Before 1950s, the main method of color vision research was psychophysical method. Its basic procedure is: under various visual stimuli, the subjects are asked to answer what they see, and then analyze the law and draw inferences. However, this method can only tell us what the visual system can do, but it can't answer how it works, and it can't analyze the receiving, coding and transmission process of color information in the visual system in detail, so it is difficult to make a correct evaluation of trichromatic theory and antagonistic color theory. In recent 20 years, with the accumulation of data and the development of new technology, the research of color vision has entered a new stage.
The research begins with the photoreceptor cells in the retina, and then advances in the order of visual information transmission. Japanese scientist Tomita is a pioneer in this field. Physiological knowledge tells us that in the retina, cone cells have the ability to distinguish colors. Professor Fukuda experimented with carp and found that there are three kinds of cones, which are most sensitive to red light, green light and blue light respectively. 1983, American scientists obtained similar results on the retina of monkeys. This confirms Thomas Young's foresight more than 50 years ago.
However, are the red, green and blue signals generated by cone cells transmitted to the brain through special lines, as assumed by trichromatic theory? Yang, a researcher at Shanghai Institute of Physiology, and hartland, a famous American neurophysiologist, denied this point through the experiments of crucian carp and frog respectively. They believe that color information is encoded by three different signals, red, green and blue, and then transmitted in the form of opposing pairs. As hartland concluded: "The century-long argument between Helmholtz and Herring seems to have been settled now: both are correct."
The long-standing debate about color vision theory seems to have subsided, but a new question has emerged: how do the trichromatic signals of cone cells encode color antagonistic pairs? Obviously, to solve this mystery, we need the help of neurochemistry, cell biology and genetic engineering technology. In order to make the mystery of color vision known to the world, we still need to explore it unremittingly.
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