6.8-bit/16-bit channel mode In grayscale RGB or CMYK mode, 16-bit channel can be used instead of the default 8-bit channel. By default, an 8-bit channel contains 256 color levels. If it is increased to 16 bit, the number of color levels of each channel is 65536, so that more color details can be obtained. Photoshop can recognize and input the image of 16-bit channel, but this image has many limitations and cannot use all filters. In addition, the image of the 16 bit channel cannot be printed. Sixth, the conversion of color mode In order to output the image correctly in different occasions, it is sometimes necessary to convert the image from one mode to another. Photoshop converts the required color mode by executing the commands in the Image/Mode submenu. This color mode conversion sometimes permanently changes the color values in the image. For example, when an RGB mode image is converted into a CMYK mode image, the RGB color values outside the CMYK color gamut are adjusted outside the CMYK color gamut, thereby narrowing the color range. Because some colors will lose some color information after conversion, it is best to save a backup file for them before conversion, so as to restore the image when necessary. 1. Convert a color image to grayscale mode When converting a color image to grayscale mode, Photoshop will discard all the color information in the original image, but only keep the gray level of the pixel. Gray mode can be used as an intermediate mode for conversion between bitmap mode and color mode. 2. Converting images of other modes into bitmap mode will reduce the image color to two, thus greatly simplifying the color information in the image and reducing the file size. To convert an image into bitmap mode, it must be converted into grayscale mode first. This will remove the hue and saturation information of pixels and only keep the brightness value. However, since only a few editing options are available for bitmap mode images, it is best to edit the images in grayscale mode and then convert them. Bitmap mode images edited in gray mode may be different after switching back to bitmap mode. For example, pixels that are black in bitmap mode may be grayed out after editing in grayscale mode. If the pixel is bright enough, it will turn white when switching back to bitmap mode. 3. Convert other modes into index mode When converting a color image into index color, many colors in the image will be deleted, leaving only 256 colors, that is, the number of standard colors supported by many multimedia animation applications and web pages. Only images in grayscale mode and RGB mode can be converted to indexed color mode. Because the gray pattern itself is composed of 256 gray levels, there is no obvious difference in color or image size after conversion into index color. However, after the RGB mode image is converted to the index color mode, the size of the image will be significantly reduced and the visual quality of the image will be damaged. 4. Convert an image in RGB mode to CMYK mode If an image in RGB mode is converted to CMYK mode, the colors in the image will be separated and the color gamut will be limited. Therefore, if the image is in RGB mode, it is best to edit it in RGB mode first, and then convert it into a CMYK image. 5. Mode conversion using Lab mode Among the color modes that Photoshop can use, Lab mode has the widest color gamut, including all colors in RGB and CMYK color gamut. Therefore, no color loss will be caused when using the Lab mode for conversion. Photoshop uses Lab mode as the internal conversion mode to complete the conversion between different color modes. For example, when converting an image in RGB mode to CMYK mode, the computer will first convert the RGB mode to Lab mode, and then convert the image in Lab mode to CMYK mode. 6. Converting other modes into multi-channel mode Multi-channel mode can be obtained by converting the color mode and deleting the color channel of the original image. Converting CMYK images into multi-channel mode can create spot colors of cyan, magenta, yellow and black (spot colors are special pre-mixed inks used to replace or supplement the printing of four-color inks; Spot color channel is a special color channel, which can add preview spot color to images. ). Converting RGB images into multichannel mode can create images composed of cyan, magenta and yellow spot colors. Deleting a channel from an RGB, CMYK, or Lab image automatically converts the image to multichannel mode. The original channel is converted into a spot color channel.