How to adjust the color of portraits in printed color images

Adjustment of portrait skin defects

Because news pictures are mostly digital pictures taken by digital cameras, they are restricted by conditions such as environment, light, and color temperature when they capture and shoot. Both the reproducibility of colors and the integrity of levels are not ideal, and there are many defects. Therefore, it is necessary to make adjustments. Can the skin color of the manuscript with defects such as color cast be adjusted to the color of the skin that meets people's psychological expectations in a limited period of time. This depends on the level and skill of the colorist. This is currently Improve color newspaper printing

The key part of portrait images is where the key lies.

In theory, this belongs to the recreative category of printing and reproduction, and it is a reflection of the artistic and artistic nature of printing technology. Some advanced newspaper printing houses attach great importance to the color adjustment before printing, and set up a number of excellent full-time coloring personnel, and at the same time strengthen the training of the aesthetics and skills of colorists to a professional level, and print high quality quickly and well. Picture of a secret weapon.

1. Color cast adjustment

Many manuscript portraits are distorted in color, with serious color casts, some yellowish, some reddish, and some grayish. Adjust to match the tone of the character's skin tone. If the original document as a whole color cast to use the level curve or correction tool for overall correction, if the facial skin color cast, then the facial part out, separate corrective.

2. Incomplete adjustment of tone

Many portraits have incomplete tones, some are high-profile, they are bright, they are bright, and they are bright and bright, and they should not be dark. Some pictures are low-key, dark, low color, you need to turn the RGB format into Lab format, use the L-lightness curve to reduce the brightness, and adjust the face of the main character to the optimal visual brightness range. Some of the larger portraits have complex skin tones, and the contrast of light is strong. The high-toned skin tone is pale like white paper, and the dark skin tone is lumpy. Should draw out the dark tone alone, through the channel separation and selection of the L channel to lighten the dark tone color, and the high light skin color Y, M color version given the printing can print out the smallest point to make it with white paper Pull distance to get the desired effect.

According to newsprint printing tone reproduction range, high-quality printing conditions, on the color separation film or CTP plate 3% to 90%, the general printing conditions of 5% to 85% of the dots can be transferred evenly to the substrate, ensuring high light 3% to 5% of the small points do not lose, dark shadow 85% to 90% of the deep points do not stick to death, to ensure complete tone.

3. Adjustment of outline imaginary

Many news photos have defective activities such as emptiness, coarse particles, and excessive magnification. The solution is as follows.

(1) Editors should choose high-resolution digital images or analog photos when designing and selecting images. Try not to download images downloaded from the Internet. If you must use online portrait photos, you should select a photo company with a panoramic view and a medium-size view. Because of its small size, it is not easy to expose shortcomings.

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

(3) Some imaginary manuscripts are moderately enhanced through Photoshop's sharpening feature layout. At the same time, in order to compensate for the sharpness of the printing process, the sharpness should be adjusted to look slightly over the screen. If the size of the portrait is larger, the particles are coarser, and depending on the specific problems, filters (speckle, dust, and scratches) and blur (Gaussian blur) in the filter can be selected to make moderate adjustments. Effect.

Pink ink configuration skin color essentials

At present, pink ink is used for color newspaper printing, which makes it harder to configure skin color.

Due to the cold color of the pink ink, such as cold solid pink ink produced by the Shanxi Ink Factory, 67.6% of the book color printing books, with gray 19.3%, efficiency 53.4%. Explained that the pink ink contains more blue components, it is arranged with yellow tone of the skin tone, and the composition of the light and dark levels of cyan, printing color changes, control is difficult. E.g:

(1) Due to the coolness of pink ink, the yellow ratio is difficult to grasp. If the yellow color is light, the skin color will be purple and gray. If the yellow color is dark, it will cause the skin color yellow and orange, which is the most taboo. The two most unsightly skin colors.

Even if you don't put blue, it will give people a gray feeling. Therefore, according to the theory of color science, "coloring material is added together, the more darker" theory, the principle of dealing with the complementary color of the skin color version is, rather than less, but the general rule is that in the red version 20% or less can not put the blue color, The cyan version of the middle tone is one-third or less of the red version.

Facial skin color processing method

1. Determine the control point of facial skin color

For the forehead, cheeks, and jaws of the face area, the forehead area should be used as a control point for skin color treatment. Because the forehead is a prominent part of the face, but also a larger area, less muscle, stable hue, because it is prominent, brighter light, so the law of its color is slightly yellow, pale yellow flesh.

2. Adjust the matching parameters of facial skin color

The red version is the main one, because the red version is an important color version of the skin color, but also a strong color, and yellow is the basic color version of the skin color, is a weak color. After determining the dot area ratio of the red version, the ratio of the yellow version is determined based on the characteristics of the character's skin color. The general rules of the proportion of flesh color on the forehead are: female skin color is yellow> red 3% to 5%, male skin color is yellow> red about 10%, the principle is that in addition to the color of infants and Caucasians, the red color of the forehead can not be greater than Yellow, if the red is greater than yellow, the face will be boring, the brightness is not enough, giving the feeling of discomfort.

3. Several skin color dot value matching parameters recorded in practice

The dot area ratio matching parameter of facial skin tone. Because the color density of each photo is different from the light and dark shades, the specific data is different, but the matching rules can be followed.

Using FM Network to Improve Picture Quality

In order to further improve the quality of color newspaper images, the newspaper industry should make new breakthroughs in ideological concepts and actively explore, experiment, and apply FM screening techniques.

When the author worked for Chengdu Business Daily Borui Printing Company, he first adopted the newly introduced high-end CTP system and gave full play to its advanced nature; the second was the use of 35-micron FM network technology, first applied to Leshan and Meishan Broadcasting and TV Newsprint. Out of the portrait photos, the skin color is real and natural, with delicate layers, which not only eliminates moiré patterns in the amplitude modulation screening, but also eliminates moire patterns on clothes and other objects, giving people a particularly comfortable visual effect and being well received by customers and readers. .

Small newspaper printing, summed up the rules of FM network printing and adjust the ideal CTP printing compensation curve, and then gradually promote the application.

The author believes that under the conditions of the equipment, technology, materials, and personnel of most printing companies in China, the use of a CTP system and the application of a 35-micron FM network are entirely feasible, so that the quality of the printing of pictures will be a new one. Steps.

It is not an easy task, but it is an important task that has to be done well and has to be improved. As long as the newspaper and printing factory leaders attach importance to using modern prepress and printing technologies, establish a color management system, strengthen the improvement of employees’ aesthetic standards and skills training, and master the laws of newsprint printing skin color, they will surely be able to print quickly and well. Produce a high-quality portrait of skin and raise the quality of portrait skin to a new level.