Color three attributes and color space composition (1)

Color has three attributes: Hue, Saturation, and Lightness.

Hue, also known as hue, is the appearance of a color, or the name of a color or the type of color, and hue has nothing to do with light and darkness. The apple is red, this red is a hue, such as red, orange, yellow, green, blue, black, purple and other basic colors. There are many types of hue, and ordinary color professionals can recognize 300 to 400. Black, gray, and white are achromatic colors.

Chroma refers to the strength of color, which can also be said to be the saturation of color, and the difference between pure and impure colors. The pure color degree exerts its inherent characteristics, in which there is no black and white blending in, the saturated color or the pure color. That is, when the solid color is mixed with black, gray, white, or other colors, the chroma will be reduced. In this case, the color of pink, pink, pink, etc. is the low chroma color, and the yellow color is the highest. , followed by orange, red, blue and purple.

The value of light refers to the degree of lightness or darkness of the color. The degree of lightness depends on the degree of closeness to white or gray. The closer to white the higher the lightness, and the closer to gray or black, the lower the lightness. For example, red has bright red or deep dark red, blue has light blue or dark blue; the highest and lowest colorless lightness is white and black respectively; among colors, yellow has the highest lightness and purple has the lowest lightness.

Additive (Subtractive) and RGB (CMY) (Additive vs Subtractive)

There are only two general methods of color reproduction, namely additive and subtractive methods, both of which are based on the theory of creating all colors in three primary colors. Understanding the principles of these two methods can understand the process of color reproduction.

1. additive process: starting from black, this involves the reflected light after the light is emitted. For the emitted light, there may be three main light waves: red, green, and blue. When combined in different proportions, a complete spectrum including all the colors is produced. Another kind of color produced by mixing any two kinds of additive main color light is called “secondary color light”. For example, a mixture of red and green light produces yellow light, red and blue light produce magenta light, and blue and green light produce blue light. Light. Equal amounts of three main colors of light produce white light. The secondary color in the additive method is indeed the dominant color in the subtractive method.

Taking three slide projectors as an example, each set of red, green, and blue color filters can illustrate how the additive method works. The light beams are adjusted so that they overlap. For example, blue filters are not "filtered out" of blue light. Waves, but blocking the red and green light waves, let the blue light through; green filter only through the green light, blocking the blue and red light; red filter only through the red light, blocking the green and blue light waves.

2. Subtractive process: Light is mainly reflected when the light passes through a pigment or a colored object and is absorbed by or subtracted from some wavelengths. The main colors of the subtractive method are three colors: cyan, magenta, and yellow. , Can be combined into red, green, blue and other secondary colors, the same combination of the three main colors should theoretically become black.

The subtractive method allows us to see the color of the surrounding objects. For example, a green ball appears green in white because the ball absorbs red and blue wavelengths and reflects green. Of course, if the light source emits only red and blue light (or magenta light), the ball will appear black, because there is no green wavelength on the green ball to reflect.

Printing also uses the principle of subtractive color. When the printing machine prints three main color inks such as cyan, magenta, and yellow on paper or other printed matter, it must use reflected light to work and reflect red, green, and The amount of blue light, color printing is the use of different sizes of halftone dots printed at different angles on a layer of paper printed on the full color, the effects of different sizes of dots and the display of different red, green and blue phosphorescence intensity similar.

The paper itself has a very important influence on color reproduction because the paper reflects unabsorbed light to the viewer and the stronger the surface reflection, such as coated paper, the wider the range of colors that can be produced.

(to be continued)