The main factors causing color distortion
1. Color distortion caused by color reproduction
Modern printing usually uses C, M, Y, K four-color inks to reproduce colors. Due to the purity problem of the ink itself, color distortion will also occur when printing.
2, color distortion caused by color separation
Printing usually uses C, M, Y, K four-color inks to reproduce colors, and the image information collected by the digital acquisition equipment to the computer is usually R, G, B information, so the image information needs to be converted into C, M, Y, K mode, that is, color separation processing.
The so-called "color separation" is to decompose and convert 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 mode. The color information will be lost during the color separation process.
During color separation, only when the separation parameters are correctly set according to the printing suitability of ink, paper, etc. (such as setting the dot expansion value, gray balance parameter, black tone, etc.), it is possible to output high-quality separation films. May reduce loss of color information.
3. Originals have color distortion
Most of the printed image originals are obtained by photographic means. For photo originals, in addition to color distortion caused by improper operation during shooting, because colors are reproduced by coloring materials such as colorants, and coloring materials are prone to color attenuation, which may also cause color distortion of photos.
In addition, with the continuous popularization of digital cameras, there are more and more digital image originals, and the technical requirements of digital cameras on operators have greatly increased. Due to the poor technical level of operators, the images taken are prone to dim screens, blurred images, etc. Problems that cause original colors to be distorted.
4. Color distortion caused by scanning
The image density of photo originals is continuous, and the image information needs to be collected into the computer. When scanning an image with a scanning device, the image needs to be divided into discrete pixels, and the R, G, and B information of each pixel on the original is collected point by point and line by line.
During the scanning process, the color information of the pixels will be lost, and the image processing is based on the collected image information. All operations on 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 important link in image processing. Improper operation will cause image color distortion.
How to distinguish color distortion
After understanding the main factors of color distortion, how to find the color distortion in the actual production process is the key.
1. First impression benchmark method
The stinging eye has some adaptability to color. For images with slightly distorted colors, repeated observations will weaken the ability to recognize.
Therefore, when judging whether or not there is color distortion, using the first impression to exclude the limitations of color vision of the human eye is an important method for discovering color distortion.
2, neutral color reference method
There are many neutral colors in life, such as black, white, gray, etc. They are the zero point of color in the colorful world, and we can use it as the base point to distinguish color distortion.
3. Skin color reference method
The color of the skin is the most familiar color. People's images, especially the portrait-based pictures, can be used as the basis for distinguishing color distortion based on the color of the skin.
Regardless of yellow skin, white skin, or dark skin, there is a regular pattern of skin color, that is, blood color. That is: red in yellow, red in white, or reddish in black. If the skin 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 during color correction, that is, red in yellow.