The main factors of printing color distortion and the identification method

　　The main factors that cause color distortion

　　1, color reproduction processing causes color distortion

　　Modern printing usually uses C, M, Y, and K four-color inks to reproduce colors. Because of the purity problems of the ink itself, color distortion occurs when printing overprints.

　　2, color separation processing causes color distortion

　　Printing usually uses C, M, Y, K four-color ink to copy colors, and the image information collected by the digital acquisition device to the computer is usually R, G, B information, so the image information needs to be converted into C, M, before printing and plate making. Y, K mode, that is, color separation processing.

　　The so-called "separation" is to decompose the color information (generally R, G, B color information) of each pixel of the image into color information suitable for printing C, M, Y, K modes. Color information is lost during the color separation process.

　　In the color separation, only according to the printing suitability of ink, paper, etc., correctly set the color separation parameters (such as setting the dot gain value, gray balance parameter, black tone tone, etc.), it is possible to output high quality color separation chips. May reduce the loss of color information.

　　3, the original has color distortion

　　Printed image manuscripts are mostly obtained by means of photography. For photo originals, in addition to color distortion caused by improper operation during shooting, since the color is reproduced by a coloring material such as a color material, the coloring material is liable to cause color attenuation, and thus may cause distortion of the color of the photo.

　　In addition, with the increasing popularity of digital cameras, digital image manuscripts are more and more, and the technical requirements of digital cameras for operators are greatly improved. Due to the poor technical level of operators, the images taken are likely to appear dim, blurred images, etc. The problem is that the original is distorted in color.

　　4, scanning processing causes color distortion

　　The image density of the photo original is continuous, and image information needs to be collected into the computer. When scanning an image with a scanning device, it is necessary to divide the image into discrete pixels, and collect R, G, and B information of each pixel on the original line by line.

　　During the scanning process, the color information of the pixel is lost, and the image processing is based on the acquired image information. All the operations on the color are also performed on this basis, and the color information of the image cannot be increased.

　　Therefore, for photo originals, scanning is a very critical part of image processing, and improper operation can cause image color distortion.

　　How to distinguish color distortion

　　After understanding the main factors of color distortion, how to find color distortion in the actual production process is the key.

　　1. First impression benchmark method

　　The human eye has a certain adaptability to color. For images with slightly distorted color, repeated observations will reduce the ability to recognize.

Therefore, when judging whether or not there is color distortion, using the impression of the first eye to exclude the limitation of the color vision of the human eye is an important method for finding color distortion.

　　2, neutral color reference method

　　There are many neutral colors in life, such as black, white, gray, etc. They are the zero points of colors in the colorful world, and we can be used as the basis for discerning color distortion.

　　3, skin color reference method

　　The color of the skin is the most familiar color. Any image of a person, especially a portrait based on a portrait, can be used as a basis for discriminating color distortion based on the color of the skin.

　　Regardless of yellow skin, white skin or dark skin, the skin color has a regular pattern, that is, it is all blood. That is: there is red in the yellow, red in the white, or red in the black. If the color of the person in the image is yellowish, it will give people a sick feeling.

　　Under normal circumstances, even if the color of the person's skin in the image is really yellow, it should be adjusted to blood color when the color is corrected, that is, there is red in the yellow.