Brief Analysis on Color Correction of Gravure Printing (Part Two)

10. The treatment of facial skin color of characters is the most difficult technology to deal with in the reproduction process, because the skin color is the most sensitive, familiar and eye-catching, and even if the skin color of printed products is slightly discolored or gray, it will produce unpleasant feelings. Therefore, it is the crown of plate-making and printing technology that the plate-making company and the electronic color-matching personnel pursue to handle the facial skin color of the characters well.

At present, there are two types of portrait photography manuscripts of gravure packaging products: one is cartoon portrait photos with small format and advertising portrait photos in packaging products; The second category is the half-length photos taken in close range, such as posters and calendars with large format. The processing essentials are as follows:
(1) cartoon and advertising portrait photo processing essentials:
(1) guiding ideology. A. First, emphasize the overall effect of skin color, make the tone of skin color accurate, and make it conform to the characteristics of the character’s skin color. Only try to catch up with the skin color effect of the color manuscript provided by the customer and the color change of each part; B. Emphasize saturated and bright skin color, that is, on the one hand, the saturation of Y and M main color plates should be sufficient in 10%-35% area, on the other hand, the content of opposite color C plate should be accurate, and generally C color should not be put below 20% of M color plate, thus highlighting the visual effect of bright, refreshing and pleasing to the eye. If you want to put a little C version of small dots that can be transferred, then what are the Y and M colors? Mace bamboo coffin: ratio of dot value of color plate.
② treatment essentials.
A. the high-gloss skin color should be distanced from the extremely high-gloss and white paper. The minimum dot value of Y and M master plates should be adjusted to be above the minimum dot value that can be transferred by printing, generally the minimum is 8%? 10%, so that one is to make the high-gloss skin full, and the other is to create conditions for printing to be transferred out of small outlets.
B. Dark skin color, if Y and M main color plates exceed 80%, it must be adjusted and controlled at 80%, and the distance between them and the real red color should be opened. Because first, more than 80% of gravure printing outlets are expanding in a straight line; Second, the dark tone on the face, the shadow on the neck, the nostrils and the dark part of the ears of most CDs are all seriously reddish. Y and M colors are all over 85%, and some even reach about 90%, while C colors are few, only 5%-10%, which can’t suppress Y and M colors, resulting in serious reddish skin color in these parts of printed products. Therefore, the main colors of Y and M, especially the M color plate, should be checked out separately with lasso tools to lighten to 75%-78%, and the C color plate should be deepened to about 25%. In this way, not only the dark skin color is calm and steady, but also the printing of full red creates favorable conditions on the spot.
C. adjust the middle tone skin color to the best visual brightness. The skin color in most CDs fluctuates greatly in the middle tone, and some of them are exposed in transition and the skin color is weak, which should be adjusted deeply. Some of them are underexposed and have dark skin color, so they should be adjusted to lighten and brighten, and all of them should move closer to the best visual brightness to give people comfortable and pleasant visual effects.
(2) Processing essentials of posters, calendars and other photographic works:
This kind of portrait photography is a high-grade product in gravure plate making, so we should make full use of the combination of gravure high-tech plate making technology and photographic art for fine processing and artistic treatment.
(1) guiding ideology. “We should give priority to the skin color of hope, and copy the realistic skin color, the original skin color and the skin color of hope in harmony and perfection”. It is emphasized that image reproduction should not only reproduce the distinctive character characteristics of portrait skin color, but also show the skin color effect that people want in their hearts. It should not only highlight the characteristics of photography art and reproduce the relationship among light, objects and shadows, but also show the three-dimensional feeling and the relationship between warmth and warmth of the face according to the laws of facial structure, color and changes of light and shadow.
Practice has proved that the color treatment of high-end product characters’ skin color is very scientific, strict and artistic, which requires that the color-adjusting personnel have high aesthetic level and artistic accomplishment, and master a set of methods and essentials of skin color treatment.
(2) Grasp the law of color expressing facial subjective feeling. Facial skin color can’t be understood as a simple expression of different shades of flesh color, but there are subtle differences between different parts, which generally have five tone color changes.
A. High gloss color: it should be close to the light source color, and it is generally a bright color with neutral white; B. Intrinsic color: the most normal color of the skin itself; C. intermediate color: located at the junction of shadows, the light gradually moves to the middle part of the dark part, and the present color phase is generally the improved inherent color, and the faded shadow color is also normal for the skin itself.
D. Shadow color: located on the whole dark side, it is most affected by the diffuse reflection light of environmental color, and its hue is cold.
E. reflective color: located in the shadow, the color is affected by the reflected light of adjacent objects. The change of color brightness of the above five tones is the basic law of color expression of facial stereoscopic impression, which tells me (a) the highlight color is skin color plus light source color:
(b) Shadow color is skin color plus environmental color; (c) Reflective color is skin color plus adjacent reflective color; (d) True skin color is expressed in intrinsic color and intermediate color.
To sum up, all visible colors and levels of the face are caused by light according to different facial shapes, and its color changes are very scientific.
(3) Grasp the color change law of the three parts of the face.
A Forehead part. The forehead is a prominent part of the face, which is a large part of the face. Because it is prominent, receives light brightly, and has few muscles in the forehead, its color is slightly yellowish and yellowish flesh.
B cheek part. Cheek is the largest part of the face, and its structure is complex. Because the muscles here are plump and covered with capillaries, the color is ruddy and full.
C upper and lower chin. The upper chin and lower chin belong to the flesh-colored system, because it is lower than the forehead and cheeks, and its hue is dark, which is the inherent color of skin color and the middle color part.
Of course, this refers to the configuration relationship of a specific person in a specific environment, and then the appropriate C color change can be configured to obtain a more varied skin color.
General beauty photos, children’s skin color. (a) forehead y >; M, 2%-3%, the skin color of individual pink babies and Caucasians can also be m >; Y； (b) cheek part, m >; Y，5％? 15%, thus charging points? The arrangement ratio of y and m is basically equal in the chin part of Jiezhannalan, which is located in Jiuji Reef.
To sum up, according to the color changes produced by the three major parts of the face, the matching proportion relationship of Y and M color plates is basically this law, which is stable. The specific value should be determined according to the characteristics of different characters and the color density of the original manuscript.
(4) Master the law of contrast of the three primary color plates with high facial tone. It is one of the key technologies to make high-quality skin color for people to master the contrast of the three primary color plates with high facial tone and fully show the rich color level changes of high facial tone. According to the law of facial light and color change, the contrast of three primary color plates is as follows:
A. Y has the strongest contrast. Therefore, the contrast of Y color should be adjusted to be larger, and Y color should be used to express the hierarchical texture and color change of high tone. Generally, the granularity of Y-color plate is coarse. Because Y-color is weak in color value, it is overprinted by delicate red, so it has no influence.
The contrast of B. C color is the weakest. For the treatment of fine facial skin color, a minimum dot value that can be transferred by printing should be put in the high tone, because according to the principle of color light, the stronger the light, the colder the hue, and the more blue-purple. Therefore, C color is used to express the color change of high tone, which adds beauty to skin color.
The lightness and contrast of C. M color are between Y and C. The contrast of highlight layer is weaker than Y color and stronger than C color. The processing of M color plate should be rich in layers, soft and harmonious, and fine in particles.
The halftone dot values of the three primary colors of typical gravure characters are YlO％%, M12％%, C5% or Y13％%, M15％%, C6%.
Practice has proved that the high tone processed according to the contrast strength of the above three primary colors is extremely wonderful and pleasant.
5. Judge the quality of electrical image and color matching From the screen, digital proof proofs, gravure ink proof proofs and printed product proofs, we can analyze and judge the quality of electronic separation and color matching from 10 aspects.
1. First of all, from the overall color tone of the picture, whether it meets the color tone of the customer sample, whether the hue of various objects is correct, whether the saturation is high or not, and whether there is color deviation.
2. Whether the color of the main part of the picture, especially the skin color of the characters, conforms to the real color of the objective object, the color that people’s psychology wants and the color that customers require, and whether it highlights the saturation of the color of the commodity.
3. Are the basic colors in the middle and dark tone areas rich in layers, are there any gradation phenomena, and are the basic colors in the light tone in the high light area and the bright tone area full? There is no loss and dull feeling.
4. Is the color from highlight to bright bright bright? Is it bright? Is it saturated? Do you feel gray and old?
5. Whether the halftone contrast of the electronic chart meets the requirements of gravure printing process, and whether there is a phenomenon that the contrast is too large or too flat. That is to say, whether there is hierarchical texture, loss or flatness in the high-gloss white of the required level.
Is the minimum dot value of OPP film printing more than 5% and 7%, and is it far away from very high gloss and white paper? Is there a hierarchy in the dark tone part, and is there a phenomenon of gradation? Is the maximum dot value of C version of the deepest part of the dark tone controlled at 90%? Is the dark flesh color of 93% people’s faces red? Whether it is controlled below 80%, and whether it is distanced from the real deep primary colors.
6. Is the color level of the main part of the picture rich? Is the color density set within the optimal visual brightness range? Whether it is too bright or too dark.
7. Is the object tone, highlight to bright tone, bright tone to middle tone, and middle tone to dark tone naturally connected? Does the hue transition continuously? There is no hard mouth or disconnection and coarse particles.
8. Whether the white, gray and black in the image are restored accurately, whether there is color bias or not.
9. Whether the image outline level and texture are clear and whether the particles are delicate.
10. To observe the whole picture in the end, it is necessary to have vivid image, bright colors, distinct layers, clear texture and delicate particles, giving people a strong color appeal that is refreshing and pleasing to the eye.