Analysis of Color Distortion

Broadly speaking, color distortion refers to the fact that the color of simulated reproduction is inconsistent with the color of the object. In the field of printing, color distortion refers to the phenomenon that the print cannot truly reproduce the color of the original, and the color of printed matter deviates from the original color. By analyzing and correcting the color of the image, it can make up for the color defects of the original and lay a good foundation for printing.

1 Main factors that cause color distortion 1) The original is distorted by color The printed image originals are mostly obtained by photography. For the photographic original, besides causing color distortion due to improper operation during the photographing process, since the color is reproduced by the coloring material such as the color material, the coloring material easily undergoes color decay, and thus may also cause photo color distortion. In addition, with the continuous popularization of digital cameras, more and more digital image manuscripts, and the digital camera's technical requirements for the operator is greatly improved, due to the poor technical level of the operator, the images taken out are prone to dim images, blurred images, etc. The problem caused the original color to be distorted.

2) Color distortion caused by scanning process

The image density of the photo manuscript is continuous and the image information needs to be captured in 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 for each pixel on the original document 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 the operations on the colors are also performed on this basis, and the color information of the images cannot be increased. Therefore, for photo manuscripts, scanning is a very critical part of image processing, and improper operation can cause image color distortion.

3) color separation caused by color distortion

Printing usually uses C, M, Y, and K four-color inks to reproduce colors, and the digital acquisition device collects computer image information that is usually R, G, and B information. Therefore, the image information needs to be converted to C, M before printing. Y, K mode, that is, color separation processing. The so-called "color separation" is the decomposition of color information (usually R, G, B color information) of each pixel of an image into color information suitable for printing C, M, Y, and K modes. Color information can be lost during color separation. In the color separation, only by the printability of ink, paper, etc., the correct setting of color separation parameters (such as setting the dot gain value, gray balance parameters, black version tone, etc.), it is possible to output high-quality color separation, May reduce the loss of color information.

4) Color distortion caused by color reproduction

Modern printing usually uses C, M, Y, and K four-color inks to reproduce colors. Because the ink itself has purity problems, color distortion may also occur during overprinting.

2 How to distinguish the color distortion

It is clear that the main factors that cause color distortion are how to find color distortion in the actual production process is the key.

1) First impression standard method

The human eye has a certain degree of adaptability to color. For images with slightly distorted colors, repeated observation weakens the ability to recognize. Therefore, when judging whether there is a color distortion, using the first impression to exclude the limitation of human eye color vision is an important method of discovering color distortion.

2) neutral color standard method

There are many neutral colors in life, such as black, white, gray, etc. They are the zero point of the colors in the colorful world. We can use it as the basis for identifying color distortion.

3) Skin color standard method

The color of the skin is the color that people are most familiar with. The image of a person, especially a picture based on the portrait of a person, can be used as the basis for identifying the color distortion based on the color of the skin. Whether it is yellow skin, white skin, or dark skin, the skin color has a regular pattern, which is all blood. That is, there is red in the yellow, red in the white, or red in the black. If the human skin color in the image is yellow, it will give people a morbid feeling. Under normal circumstances, even if the color of the human skin in the image is really yellow, it should be adjusted to blood color in color correction, that is, red in yellow.

4) Key color standard method

The key color is the memory color, such as the blue of the sky, the green of the grass, etc. Memory color is the most common color in life. As a prepress staff, we should strengthen the training of memory colors, observe carefully in peacetime, constantly perform visual training and accumulate experience, and use our memories to restore the original colors of the images in school colors.

3 color correction