Method for adjusting the color of portraits in printed color newspapers

Adjustment of portrait skin defects

Since news pictures are mostly digital pictures taken by digital cameras, they are constrained by the environment, light, color temperature and other conditions when capturing and snapping. Both the reproducibility of color and the integrity of the hierarchy are not ideal, and there are many defects. Therefore, it is necessary to carry out adjustment processing. Whether or not the skin color of the manuscript with defects such as color cast can be adjusted to the skin color that people psychologically hope within a limited time depends on the level and skill of the colorist. This is the current The key link to improve the portrait printing of color newspapers is the key point.

In theory, this belongs to the re-creation category of printing and copying, and is the artistic expression of printing technology. Some advanced newspaper printing plants attach great importance to the pre-press grading process, and set up a number of excellent full-time color grading personnel, and at the same time strengthen the aesthetic and technical training of color grading personnel to reach a professional level, as a fast and good quality Picture of a secret weapon.

1. Adjustment of color cast

Many manuscripts have distorted skin tones, severe color casts, some yellowish, some reddish, and some grayish. By adjusting it to match the character's skin tone. For example, if the overall color of the original document is color-shifted, a gradation curve or color correction tool will be used for the overall correction. If the skin color of the face is color-shifted, the face will be partially hooked out and corrected separately.

2. Incomplete adjustment

Many portrait pictures have incomplete gradation, some are high-profile films, bright, high color lightness, should be adjusted to a bright and bright complexion, and avoid gray. Some pictures are low-key films, darker, and low color brightness, you need to convert the RGB format to Lab format, use the L brightness curve to lighten and brighten, and adjust the main character's face to the best visual brightness range. Some portraits with large areas have skin tones with strong light contrast, high-brightness skin tones are as pale as paper, and medium-dark skin tones are clumped together. The mid-dark tone should be selected separately, and the L channel should be selected through the channel separation to lighten and lighten the mid-dark tone skin tone, and the Y and M color versions of the high-gloss skin tone should be printed to the smallest point that can be printed out with the white paper Open the distance to get the desired effect.

According to the range of newsprint printing tone reproduction range, high-quality printing conditions, 3% to 90% on color separation films or CTP plates, general printing conditions are 5% to 85% of the dots can be transferred to the substrate evenly, to ensure high gloss 3% to 5% of the small dots are not lost, and the dark tone is 85% to 90% of the deep dots are not sullied, ensuring the complete tone.

3. Adjustment of the outline

Many news pictures have defects such as fuzziness, coarse particles, and excessive magnification. The solutions are as follows.

(1) When designing and choosing pictures, editors should try to choose high-resolution digital pictures or analog photos, and try not to choose pictures downloaded online. If you must choose portrait photos on the Internet, you should choose panoramic and mid-range photo companies. Because of its small portrait, it is not easy to expose shortcomings.

(2) The pixel value of the digital camera is fixed, it should be changed to an appropriate size after calculating the pixel value, and try not to magnify it.

(3) Some manuscripts are dullly enhanced by Photoshop's sharpening function layout design. At the same time, in order to compensate for the decrease in the definition of the printing process, it is better to adjust the definition so that it looks a little excessive on the screen. If the skin color of the portrait is larger and the particles are coarser, you can choose tools such as noise (speckle removal, dust and scratches) and blur (Gaussian blur) in the filter to adjust it according to the specific problems. Effect.

How to configure skin color with pink ink

Currently, pink ink is used for color newspaper printing, which makes it difficult to configure the skin color. Due to the cold color of the pink ink, such as the cold solid pink ink produced by Shanxi Ink Factory, the color deviation is 67.6% for book printing, with gray 19.3%, and the efficiency is 53.4%. It shows that the pink ink contains more cyan components. It sets the tone of the skin color with yellow and the light and dark layers with cyan. The color changes greatly during printing and the control is difficult. E.g:

(1) Due to the coldness of the pink ink, the proportion of yellow is difficult to grasp. If the yellow is light, it will cause the skin to be more purple and gray; if the yellow is darker, it will cause the skin to be more yellow and orange, which is the most taboo , The two most ugly skin tones.

Even if you don't put cyan, it will make people feel gray. Therefore, according to the theory of chromatics "addition of colorants, the darker the darker", the processing principle of the complementary color of the cyan version of the skin color is, rather than less, the general rule is not to put cyan under 20% of the red version. The cyan version of the middle tone skin tone is 1/3 or less of the red version. [next]

Facial skin color processing method

1. Determine the control points of facial skin color

The forehead, cheeks, and chin of the portrait area should be used as the control point for skin color treatment. Because the forehead is a protruding part of the face and a larger area, it has fewer muscles and a stable hue. Due to its protruding and brighter light, the coloring rule is slightly yellowish and pale yellow.

2. Adjust the matching parameters of facial skin tone

First, the red version is the main one, because the red version is an important color version of skin tone, and it is a strong color, while yellow is the basic color version of skin tone, which is a weak color. After the area ratio of the red version of the dot is determined, the proportion of the yellow version is determined according to the characteristics of the person's skin color. The general color matching rule of the forehead is: female skin color is yellow> red 3% ~ 5%, male skin color is yellow> red about 10%, the principle is that except for the skin color of young children and Caucasians, the red color of the forehead cannot be greater than Yellow, if the red is greater than yellow, the face will be dull, the brightness is not enough, giving people an uncomfortable feeling.

3. Practical record of matching parameters of several skin tone dot values

The matching parameter of the dot area ratio of facial skin color. Since the color density and the change of light and shade of the skin color of each photo are different, the specific data is different, but the law of matching can be followed.

Adopt FM network to improve the quality of color picture pictures

In order to further improve the quality of color newspaper pictures and unemployment, newspaper professionals should make new breakthroughs in their ideology and concepts, and actively explore, experiment, and apply FM screening technology.

When I was working in the Chengdu Commercial Daily Borui Printing Company, one was to adopt the newly introduced high-end CTP system to give full play to its advanced nature; the other was to use the 35-micron FM network technology, which was first applied to Leshan and Meishan radio and television newspapers. The portrait photos produced have real and natural skin tones and delicate layers, which not only eliminates the moiré in amplitude modulation and screening, but also eliminates the moiré on clothes and other objects. It gives a particularly comfortable visual effect and is praised by customers and readers. .

For small newspaper printing, summarize the law of FM screen printing and adjust the ideal CTP printing compensation curve, and then gradually promote the application.

The author believes that under the current conditions of equipment, technology, materials, personnel, etc. of most newspaper printing companies in China, it is completely feasible to adopt the CTP system and apply a 35-micron FM network, so that the quality of the printed pictures will be on a new Stairs.

It is not an easy task, but it is an important task that has to be done well and improved. As long as newspaper and printing company leaders attach importance to the use of modern prepress and new printing technologies, establish a color management system, strengthen the improvement of employees' aesthetic level and skill training, and master the law of the color of newsprint printing, they will be able to print quickly and well. Produce high-quality portrait skin tones and improve the printing quality of portrait skin to a new level.

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