Photoshop color mode complete manual (a)

In Photoshop, understanding the concept of a pattern is important because the color mode determines the color model for displaying and printing electronic images (simply the color model is a mathematical algorithm for representing colors), ie what an electronic image is like The way is displayed or printed out on the computer. Common color modes include bitmap mode, grayscale mode, dual tone mode, HSB (Hue, Saturation, Brightness) mode, RGB (red, green, blue) mode, CMYK (representing cyan, magenta, yellow, black) ) Mode, Lab mode, Index color mode, Multi-channel mode, and 8-bit/16-bit mode. The principle of image description and reproduction of colors in each mode and the number of colors that can be displayed are different.

In addition to determining the number of colors that can be displayed in an image, the color mode also affects the number of channels and the file size of the image. The channels mentioned here are also an important concept in Photoshop. Each Photoshop image has one or more channels. Each channel stores information about color elements in the image. The default number of color channels in an image depends on its color mode. For example, CMYK images have at least four channels and the resolutions represent cyan, magenta, yellow, and black information. In addition to these default color channels, an extra channel called an alpha channel can also be added to the image to store and edit the selection as a mask, and a spot color channel can be added. An image sometimes has as many as 24 channels. By default, there is still one channel in the bitmap mode, grayscale duotone, and index color images; there are three channels for RGB and Lab images; and four channels for CMYK images.

One, HSB mode

HSB mode is defined based on the human eye's observation of color. In this mode, all the colors are described by hue or hue, saturation, and brightness.

1. Hue (H)
Hue is the physical and psychological characteristics of the color associated with the dominant wavelength of the color. It is known from experiments that different wavelengths of visible light have different colors. Many wavelengths of light can be mixed in different proportions to form a variety of colors, but as long as the wavelength composition is certain, then the color is determined. Non-color (black, hundred, gray) does not have a hue attribute; all colors (red, orange, yellow, green, cyan, blue, purple, etc.) are attributes that represent the appearance of the color. They are all hue, and sometimes hue is also called hue.

2. Saturation (S)
Saturation refers to the intensity or purity of a color, and represents the proportion of the gray component in the hue, expressed as 0%-100% (pure color).

3. Brightness (B)
Brightness is the relative darkness of the color and is usually measured in 0% (black) - 100% (white).

Second, RGB mode

The RGB mode is based on the principle of the mixture of the three primary colors in the natural world. The primary colors of red (R), green (G), and blue (B) 3 are in each color from 0 (black) to 255 (white). Assigned in the order to specify its color. When the base colors of different brightness are mixed, 256*256*256 colors will be produced, which is about 16.7 million kinds. For example, a bright red may have an R value of 246, a G value of 20, and a B value of 50. When the luminance values ​​of the three primary colors are equal, a gray color is generated; when the three luminance values ​​are both 255, pure white is generated; and when all the luminance values ​​are 0, a pure black color is generated. When the colors produced by the three kinds of color light blends are generally higher than the original color luminance values, the method of generating colors in the RGB mode is also called the color light additive method.

Third, CMYK mode

CMYK color mode is a printing mode. Four of the four letters are Cyan, Magenta, Yellow, and Black, and four colors of ink are represented in printing. The CMYK mode is essentially the same as the RGB mode except that the principle of color generation is different. In the RGB mode, the color light emitted by the light source is mixed to generate colors. In the CMYK mode, the light is irradiated with different ratios C, M, and Y. On K-ink paper, some of the spectrum is absorbed and the light reflected by the human eye produces color. Since C, M, Y, and K are mixed together, as the four components of C, M, Y, and K increase, the light reflected by the human eye becomes less and less, and the brightness of the light becomes lower and lower. The method of generating colors in the CMYK mode is also called subtractive color.

Fourth, Lab mode

The prototype of the Lab model was a standard for color measurement developed by the CIE Institute in 1931. It was redefined in 1976 and named CIELab. This mode solves the difference in color fostering due to different displays and printing devices, that is, it does not depend on the device.

The Lab color represents the color with one luminance component L and two color components a and b. Where L ranges from 0 to 100. The a component represents the spectral change from green to red, while the b component represents the spectral change from blue to yellow. Both a and b range from -120 to 120.

Lab mode contains the widest range of colors and can include all colors in RGB and CMYK modes. The CMYK mode contains the least color, and some of the machete colors on the screen cannot be realized on the print.

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