Basic knowledge of color theory (4)

Fourth, opposition color theory

In the previous article, we made a detailed discussion on the color vision theory of "the three primary colors of visual colors". Next, we will continue to study "the theory of color opposing colors". In 1878, the German physiologist Ewald, according to the observation of psychophysical research, found that red-green, yellow-blue, black-white always showed a color phenomenon of the opposite relationship; also said that red and green, yellow and Blue, black and white cannot exist in any color sense at the same time. So Hering proposed the Opponent Colors Theory or Opponnyt Process Theory, which assumes that photoreceptor cells in the visual mechanism have the above three opposing colors. According to the above assumptions, it can be known that the Hering doctrine asserts: “The color space belongs to the third dimension, which is the three bipolar coordinates of red-green, yellow-blue, and black-white, and the three opposite colors. The combination of reaction effects produces a variety of color perceptions and various color mixing phenomena." Therefore, Hering's "antagonism theory" is also called the "four-primary color theory" because he believes that producing various color sense phenomena is formed by four colors: red, green, yellow and blue.

Hering's theory of "standing color theory" was proposed to explain the following facts and phenomena:

1. Complementary color afterimage: This phenomenon is because when a certain color thorn stops, the opposite color associated with the color starts to act, and thus the opposite color of the color is produced—complementary color.

2. Simultaneous comparison: When the retina is undergoing a stimulating reaction of a pair of opposing colors, its adjacent part will produce the phenomenon of simultaneous contrast.

3. Color blindness phenomenon: Since color blindness is caused by a pair of (red-green or yellow-blue) pairs of human eyes, or two pairs of opposing color reaction processes cannot be performed, color blindness often occurs in pairs, ie, color blindness is usually It is red-green blind or yellow-blue blind, and when two pairs of opposing reaction processes cannot be performed, full-color blindness occurs. This argument explains the inconsistency of the theory of “visual color trichromatics” in previous color vision theory. Color blindness.

Even so, Hering's doctrine has its own shortcomings, that is, the phenomenon that the three primary colors of red, green and blue can produce all spectral colors cannot be satisfactorily explained. However, Hering's antithesis theory is a very important academic theory in colorimetry theory in recent years. The most obvious example is that the color space coordinates of CIE Lab, Luv, etc. are all using the opposition of Hering. , Red-green, yellow-blue, black-white three coordinates, so Hering's color vision theory is also a very important basic theory for modern colorimetry.

Fifth, stage visual color theory

The stage color theory was first proposed by GEMuller (1930) and Judd (1949). They believe that for a long time, the three-primary color theory and the opposing color theory, which have been opposed to each other in the Color Vision Theory, have been After experimental studies, it is proved that the two can be integrated and coordinated with each other, and the phenomenon of human eye color vision is more fully explained and explained. But how does the phase visual color theory integrate the four opposing color metabolic reaction processes of the "Contradictive Color Theory" with the "three-primary theory of visual color"? I will try to discuss it below.

When light enters the retina of the human eye, the photo pigments in the cone cells selectively absorb radiation of different wavelengths, and each type of cone-shaped cells can generate lightness independently according to the amount of light stimulation ( Black or white) reacts with color (red, green, blue). In this stage, Young-Helmholtz's theory of visual color primaries and color mixing experiments can be applied to explain the phenomenon of visual color.

As the cone cells are connected with the optic nerve cells, the nerve impulses caused by the light stimulation of the cone cells will form a visual color signal. The signal content is analyzed as follows:

(1) achromatic signal - responsible for the integration of the brightness signal, receiving a photopic achromatic signal formed by the three cone cells.

(2) The chromatic signal - responsible for the integration of the color signal, received by the three cone cells.

The color signals such as red, green, and blue are formed; at this stage, the color signals are represented by the following three color-difference signals: C1=RG; C2=GB; C3=BR (R, G, and B represent three types, respectively. Cone cell signal). When these three color-difference signals C1, C2, and C3 are transmitted through nerve fibers to the nerve center, they are generated and integrated into two color signals, which are C1 and C3-C2.

Therefore, three pairs of opposing nerve impulse responses are formed during this phase. The signals are as follows:

(1) Lightness signal.........the opposite of black and white

(2) Color signal C1.........Red and green

(3) Color signals C3-C2.........Yellow and blue opposition colors

In response to the transmission of light stimulation from the cone to the nerve center, the three pairs of opposing nerve impulses responded, just in accordance with Hering's theory of the opposing color.

If we use the following figure to illustrate the above text description, we can clearly understand how the stage visual color theory integrates two visual color theories to produce color visual phenomena.

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