The color mode of Photoshop

1, RGB mode

　　
RGB is the color mode of the shade. R for Red, G for Green, b for blue, three colors for other colors. Because three colors have 256 levels of brightness level, so three color overlay on the formation of 16.7 million colors. That is true color, through them enough in the now gorgeous world.
　　

In RGB mode, the overlay of red, green, and blue can produce other colors, so the pattern is also called the color-adding mode. Many devices, such as monitors, projection devices, and televisions, depend on this color-adding mode.

　　
In the case of editing images, RGB color mode is also the best color mode, because it can provide a full screen of 24bit color range, that is true color display. However, if you use RGB mode for printing is not the best, because RGB mode provides some colors are beyond the scope of printing, so in the printing of a true color image, it will inevitably lose a part of the brightness, and the more vivid colors will certainly be distorted. This is mainly because the printing is CMYK mode, and CMYK mode defined color than RGB mode definition of a lot of color, so when printing, the system will automatically convert RGB mode to CMYK mode, which will inevitably lose part of the color, the phenomenon of printing distortion.

2, CMYK mode

　　
When the sun shines on an object, the object absorbs part of the light and reflects the rest of the light, which is the color of the object we see. This is a subtractive color mode, but also with the RGB mode is fundamentally different. Not only do we use this subtractive pattern when we look at the color of an object, but it is also used when printing on paper.

　　
According to this kind of subtractive mode, the CMYK color mode which is suitable for printing is developed.

　　
CMYK represents four colors for printing, C for cyan, m for magenta, Y for yellow, and K for Black. Because in actual quotes, cyan, magenta, and yellow are hard to overlay to form real black, most of which is brown. Hence the introduction of k--black. The role of black is to strengthen the dark tone, deepen the dark color.

　　
CMYK mode is the best printing mode, RGB mode, although many colors, but not fully printed out. Then is not in the editing of the use of CMYK mode it? No, for the following reasons:

　　
Using CMYK mode editing can avoid the loss of color, but the operation speed is very slow. Because: 1, even in the CMYK mode of work, Photoshop must also convert the CMYK mode to the display of the RGB mode used. 2, for the same image, RGB mode only need to handle three channels, and CMYK mode will need to deal with four >

　　
Because the user uses the scanner and the monitor is the RGB device, therefore whenever uses the CMYK mode to work has to convert the RGB mode to the CMYK mode such a process.
　　

Therefore, whether to apply CMYK mode for editing is a problem in RGB mode and CMYK mode conversion.

　　
Here is a suggestion, it is a bit of my experience. First use RGB mode for editing work, and then use CMYK mode for printing, before printing before the conversion, and then add the necessary color correction, sharpening and trimming. This allows Photoshop to be slower in CMYK mode, but saves most of the editing time.

　　
In order to quickly preview the display of images in CMYK mode, the CMYK Preview (CMYK preview) commands under the View menu are available without conversion mode.

　　
This mode conversion before printing is not the best way to avoid the loss of image, the best way is to combine lab mode and CMYK mode, which can reduce image distortion to the greatest extent. Lab mode is described below.

3, Lab Mode

　　
Lab mode is an international Lighting Commission (CIE) in 1976 (Wow, it's so far away.) ) published in a color pattern.

　　
You already understand: RGB mode is a light-emitting screen of the color mode, CMYK mode is a color reflective printing subtractive mode. So what does lab have to do with the model?

　　
Lab mode relies neither on light nor on pigments, which is a color pattern that the CIE organization has theoretically included in all colors visible to the human eye. Lab mode compensates for the lack of RGB and CMYK two color modes.

　　
Lab mode consists of three channels, but not the R, G, B channels. One of its channels is brightness, that is, L. The other two are color channels, represented by A and B. A channel includes a color from dark green (bottom brightness value) to gray (medium brightness value) to bright pink (high brightness value), B channel from bright blue (bottom brightness value) to gray (medium brightness value) to yellow (high brightness value). Therefore, this color mixture will produce bright colors.
　　

Lab mode defines the most colors and is independent of light and equipment and processing speed is as fast as RGB mode, much faster than CMYK mode. Therefore, you can be assured of the bold use of lab mode in image editing. Also, the color is not lost or replaced in the lab mode when it is converted to CMYK mode. Therefore, the best way to avoid color loss is to apply Lab mode to edit the image and then convert it to CMYK mode for printing output.
　　

When you convert RGB mode to CMYK mode, Photoshop automatically converts RGB mode to lab mode and then to CMYK mode.

　　
In the expression color range, in the first place is Lab mode, the second is RGB mode, the third is CMYK mode.

4, HSB mode

　　
After introducing the three main color patterns, now introduce another color mode--HSB color mode, which will appear in the Color-absorbing window.

　　
In HSB mode, h denotes hue, S is saturation, and B indicates brightness.

　　
Hue: is a solid color, that is, a monochrome composition of the visible spectrum. Red at 0 degrees, green at 120 degrees, blue at 240 degrees. It is basically RGB mode full chroma pie chart.

　　
Saturation: Indicates the purity of the color, when 0 is the color. White, black and other shades of gray are not saturated. At maximum saturation, each hue has the purest shade.

　　
Brightness: Is the bright color of the reading. is black for 0 o'clock. Maximum brightness is the most vivid color of the state.

5, indexed mode

　　
The indexed mode is the indexed color pattern, also known as the mapping color. In this mode, you can only store a 8bit color depth file, which is up to 256 colors, and the colors are predefined. A picture of all colors are defined in its image file, which is to map all the colors to a color plate, which is called the color comparison table. Therefore, when the image file is opened, the color comparison table is also read into Photoshop, Photoshop from the color comparison to find the final color value.

　　
6, Grauscale mode
　　

After the introduction of the gorgeous color of the world, now into the gray world. In fact, Gray is also a kind of color, there are gorgeous side.
　　

Grayscale files are 8bit images that can be composed of up to 256 levels of gray, and brightness is the only factor controlling grayscale. Brightness is about high, the lighter gray, the closer to the white, the more the brightness of the bottom, the deeper the gray, the closer to the black. Therefore, black and white are included in grayscale, which is a subset of grayscale patterns.

　　
Grauscale mode

　　
and grayscale mode. Only grayscale exists in grayscale mode. When a color file is converted to a grayscale file, all color information is removed from the file. Although Photoshop allows a grayscale file to be converted to a color-mode file, it is not possible to return the original color to the slightest change.

　　
In grayscale files, the color saturation of the image is 0, and brightness is the only option that can affect the gray image. Brightness is a measure of light intensity, 0% represents black, and 100% represents white. The k value in the color palette is used to measure the amount of black ink.

7, Bitmap mode

　　
Black-and-white bitmap mode is only black and white pixels composed of two images, some people think that since Black is a subset of grayscale color mode, so this model is not much use. In fact, this is a false understanding, because of the bitmap mode, can be more complete control of gray-scale image printing output. In fact, such as laser printers such as output devices are small points to render grayscale images, so using the bitmap mode can be better to set the size of the dot shape and the angle of each other.

　
Note that only grayscale images or multichannel images can be converted to bitmap mode, and the conversion will appear with a dialog box where you can set the output resolution and the way the file is converted. The specific settings are as follows:

　　
Output: The resolution of a black-and-white image.

　　
Method (Mode): provides the following 5 kinds of settings.

　　
50%threshold (critical value): When selected, grayscale pixels greater than 50% will become black, and grayscale images less than or equal to 50% will become white.
　　

Pattern dither (Image jitter): Use some random black-and-white pixels to dither the image. Images generated using this method are difficult to see, and there is little space between pixels.

　　
Diffusion dither (diffusion jitter): Use this term to produce a metal version effect. It will use a divergence process to change a pixel into monochrome, and the result is a particle effect.
　　

Halftone screen (half color): This conversion makes the image look like a grayscale image printed on a half color screen.
　　

Custom pattern: This conversion method allows a custom pattern to be added to a bitmap image (with the pattern defined by the custom Patterns command in the Edit menu).

Note that when the image is converted to bitmap mode, no other edits can be made, and even the image in grayscale mode cannot be restored.

　　
8, Duotone double color sleeve mode

　　
Duotone mode with a grayscale ink or color ink in the rendering of a grayscale image, for Two-color overprinter or the same color bias overprinter mode. In this mode, you can add a maximum of 4 colors to a grayscale image, so that you can print a lot better image that is much larger than the pure grayscale pattern.