"Gravure image color" processing techniques, methods and essentials (2)

Treatment of facial skin color

The facial skin color of the character is the most difficult technique in the reproduction process, because the skin color is the most sensitive, the most familiar, the most eye-catching, even if the skin color is slightly color cast, a little dark, it will produce an unpleasant feeling. Therefore, dealing with the facial skin color is the crown of plate-making and printing technology pursued by the plate-making company and the electric color-dividing personnel.

At present, there are two types of portraiture manuscripts for gravure packaging products: one is for portraits with small format portraits and advertising portraits in packaging products; the other is for half size photos with large format posters, wall calendars and other close-range shots. The processing method is as follows:

(1) How to deal with cartoons and advertisements like photos:
1 The guiding ideology. A. First of all, emphasize the overall effect of skin color, so that the tone of the skin tone is accurate, so that it meets the characteristics of the skin color of the character, only requires the customer to provide as much as possible color skin color effect, do not have to emphasize the facial skin color changes in various parts; B. Emphasizes that the skin color is saturated and bright, that is, on the one hand, Y, M main color version in the region of 10% -35% saturation should be sufficient, on the other hand, the reverse C version of the content to be accurate, generally 20% below the M color version does not put C Color, thereby highlighting the overall bright and bright skin tone, refreshing visual effects. If you want to put a little dot of C version that can be transferred, then the Y, M color quantity should reach the ratio of the dot value that can suppress the C color version.

2 processing essentials. A. High-gloss skin color should be separated from extremely high light and white paper. The minimum dot value of the main color version of Y and M should be adjusted to the minimum dot value that can be printed out by printing. Generally, the minimum dot value is 8% to 10%. This is to make the glossy skin color full, and the second is to create a small outlet for printing. condition. B. Dark skin color, if the Y, M main color version more than 80%, it must be adjusted to control below 80%, to pull away from the field red. Because the first is that more than 80% of the gravure printing points are linearly expanding; secondly, most of the CD's dark shadows, neck shadows, nostrils, and dark shadows are all heavily reddish. The Y and M colors are all above 85%, and some even reach About 90%, but C color is very small, only 5% -10%, can not hold back the Y, M color, resulting in these parts of the printed product skin color is heavily reddish. Therefore, the Y, M main colors, especially the M color version, should be used to separate the reddish parts with a lasso tool, adjust the lightness to 75%-78%, and deepen the C color version to about 25%. This will not only make the dark part of the skin calm and stable, but also to create a favorable condition for printing the printed red feet. C. Adjust skin tone to optimal visual brightness. In most CDs, the tone of the skin changes greatly, and some of the transitions are light and thin. Some underexposure, dark skin color, should be used to reduce light and bright adjustments, should be closer to the best visual brightness, giving people a pleasant visual effect.

(2) How to deal with portraitures, wall calendars, and other portraiture works:
This type of portrait photography is a high-end product in the gravure printing plate. It should make full use of the combination of gravure high-tech plate making technology and photography art for fine processing and art processing.

1 The guiding ideology. "It should be based on the hope that the skin color is the main theme, and the perfect harmony between the realistic skin color, the original skin color and the desired skin color." Emphasizing that image-reproducing copying should not only reproduce the vivid character features of the human skin color, but also demonstrate the skin color effect people want. It must highlight the characteristics of the photographic art and reproduce the relationship between light, material, and shadow, as well as the facial structure. The law of color and light changes shows the three-dimensional sense of the face and the relationship between cold and warm.

Practice has proved that the color processing of high-end product people's skin color is very scientific, strict and artistic, and requires electric color-grading personnel to have high aesthetic standards and artistic accomplishments, as well as a set of methods and essentials to master skin color processing.

2 Master the rules of color expression of facial sense. Facial skin color can not be understood as a purely different shade of flesh color performance, but there are subtle differences between the various parts, generally with five tones of light and shade changes.

A. High light color: should be close to the light source color, generally a neutral white bright color;
B. Intrinsic color: the most normal color of the skin itself;
C. Middle color: At the border of the shadow, the light gradually moves to the middle of the dark part, showing the natural color that the hue is generally improved, and the light color that is lightened is also the normal color of the skin itself.
D. Shadow color: Located on the entire dark side, affected by the ambient diffuse reflection light, the hue is cooler.
E. Reflective color: located in the shadow, the color is affected by the reflection of light from nearby objects. The above-mentioned five kinds of tone changes in light and dark colors, is the basic law of color expression facial three-dimensional, this law tells us the following four points:

(A) The highlight color is the skin color plus the light source color:
(B) The shadow color is skin color plus ambient color;
(C) The reflective color is the skin color plus the adjacent reflected color;
(D) True skin color manifests itself in neutral colors.
In summary, all the visible colors and layers of the face are caused by the light in different facial shapes, and the color change is very scientific.

3 Grasp the pattern of color change produced by the three major parts of the face.
A forehead portion. The forehead is the part of the face that protrudes. It is a part of a larger area of ​​the face. Because it is prominent, the light received is brighter, and the frontal muscles are also less, so its color is slightly yellowish and pale yellow.
B cheek section. The cheek is the largest part of the facial area, and the structure is complex. Because the muscles are plump here, and the muscles are covered with capillaries, the color is ruddy and plump.
C up and down part. The upper part of the jaw is a flesh-colored system, because it is smaller than the forehead and cheeks. It is in the lower part of the face, and the hue is dark. It is the inherent color of the skin color and the middle color part.
Of course, this refers to the configuration of a particular person in a particular environment. After the appropriate C color change is configured, a more varied skin tone can be obtained.

General beauty photo, children's skin color. (A) Forehead portion Y>M, 2%-3%, skin color of individual pink infants and whites, but also M>Y; (B) cheeks, M>Y, 5% to 15%, and thus sufficient Shows the beauty of two red cheeks: (C) Under the jaw, the ratio of Y and M is almost equal.

In summary, according to the color changes produced by the three major parts of the face, the proportion of Y, M color version of the layout is basically the law, is stable, as to the specific value according to different character characteristics, and the original color density situation And set.

4 Grasp the law of the contrast of the three primary colors of the face with high light intensity. It is one of the key technologies for producing high-quality character skin color by mastering the contrast of the three-primary version of the high-gloss face, and fully displaying the rich color-level changes of the high-light tone. According to the rules of facial light and color change, the contrast of three primary colors is:

A. The Y color has the strongest contrast. Therefore, it is necessary to adjust the contrast of the Y color to be larger, and to express the texture and color change of the high-light tone with the Y color. The Y-color version has a coarser grain size. Since the Y color is weak in color, it is superimposed on the delicate red color, so there is no effect.
B. The C-color contrast is the weakest, and the fine-skinned facial skin color treatment, high-light tone should be put in a printing can transfer the minimum dot value, because in accordance with the principle of color light, the stronger the light, the cooler the hue, bluish purple. Therefore, the use of C color to express high-toned color changes, add beauty to the skin.
C. The brightness of M color and the contrast are all between Y and C. The contrast of the highlight layer is weaker than the Y color, and it is stronger than the C color. The processing of the M color version needs to be rich in levels, yet it must be soft and harmonious, and the particles must be delicate.

Typical gravure prints with high-toned tri-color dot values ​​are YlO%, M12%, C5% or Y13%, M15%, C6%.
Practice has proved that a high light tone processed according to the contrast of the above three primary colors is extremely exciting and enjoyable.

Judging the quality of electrical subdivision and color correction From the screen, digital proofs, gravure ink proofs and proofs of printed products, we can analyze and judge the quality of electrical subdivisions and toning from 10 aspects.
1. First of all, from the perspective of the overall tone of the picture, whether it meets the tone of the customer's sample draft, the hue of various objects is not correct, the saturation is not high, and there is no color cast.
2. The color of the main part of the screen, especially the color of the characters, is in line with the true color of the objective reality and the color desired by the people's psychology and the color requested by the customer, whether it highlights the attributes of the product and emphasizes the saturation of the color.
3. If the object is in tune, is the basic color of the dark tone region rich in levels, whether there is a merging phenomenon, or if the highlight region is bright, and if the basic color of the light tone region is full or not, there is no loss or feeling of peace.
4. Is the color of high-light to bright tone bright and bright? Is it bright, is it saturated, or is it dark and old?
5. Whether the dot contrast of the dot pattern of the electricity subgraph meets the requirements of the gravure printing process and whether there is a phenomenon that the contrast is too large or too flat. That is, whether the level of high-gloss white needs a layered texture, and whether it has a loss or flat gray feel.

Whether the minimum dot value of the OPP film printing reaches 5% to 7% or more, and whether the highlight light and the white paper are separated from each other, whether the dark tone portion has a level, whether there is a leveling phenomenon, and the darkest tone is the deepest part of the C version maximum dot value. Is it controlled at 90% to 93%? Is the dark flesh of the person's face exposed to red? Whether it is controlled below 80% or not, is it a matter of distance from the deep original color in the field?
6. Is the color level of the main part of the screen abundant? Is the color density set within the optimal visual brightness range? Is there an overly bright or too dark defect?
7. Object tones, high light to bright tone, bright tone to the middle tone, middle tone to dark tone convergence natural? Hue whether continuous transition? There is no hard mouth or dislocation and coarse particles and other ills.
8. Whether the white, gray or black in the image is accurate, whether there is color cast or dew.
9. Image outline level, texture is clear, whether the particles are delicate.
10. In the end, the entire picture is observed, and the main subject is clear-cut, colorful, structured, clear in texture, and exquisite in grain, giving people a refreshing and intense color appeal.

Source: Printed in China