Techniques, methods and essentials for color processing of gravure images (serial 2)

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8. Original color cast processing

At present, many original color patterns have various color casts. Therefore, the correction of the ground color is an important content in the color matching operation, and the following essentials should be mastered:

(1) Color cast positioning:

First, analyze whether the color of the original (including light, disk) is color cast? Typical color casts are mainly expressed in the neutral gray and the color portion of the impression. When positioning the color cast, one depends on the eye; the second is to use the suction tool to determine the dot value and the company's gray balance value to determine whether the color cast. Method for visual recognition of color cast:

1 See if the black, white or gray in the image is color cast, because people are correct for ink, white and gray, as long as the black, white and gray in the picture are correct, the original color is correct.

2 See the color of the most familiar part, such as the color of the person's skin, whether it matches the skin color of the child, the color of the young woman, the skin color of the actor, etc., whether it meets the skin color desired by people's mind, whether it is yellowish, reddish, grayed, etc. defect.

3 Look at the important impression colors in the image, such as big red, green, orange, tomato, banana, walnut, strawberry, etc., whether it matches the true color of the objective object in the impression, whether it is with the color of the color provided by the customer. Match, there is no color cast.

(2) What color is determined?

1 Based on black, white and gray, look at the black, white and gray colors, which are blue, reddish or purple.

2 Based on the skin color of the character's characteristics, combined with the skin color desired by people's minds, it is yellowish, reddish, or grayish or dark.

3 Based on the actual color of the objective object, according to the requirements of the customer, look at the important color of the various subjects. For example, if the red color is partial magenta or orange red; if the green color is greenish or yellowish green, it is still grayish; if it is orange, the orange color is yellowish and lacking magenta, or the partial red is yellow, or gray. Only accurate determination of color cast, what color? In order to carry out the correct correction.

(3) Correction method:

1 white tone correction: First, as the white tone has a layered texture, the high-light end tool that applies the level curve, according to the neutral white point value ratio correction, and the second is the white tone has no level, then you can choose the white block in the school color Tool correction.

2 Middle adjustment gray correction: using the middle tool of the gradation curve, according to the neutral gray grid point value correction, should pay attention to two situations:

First, it is necessary to observe whether the size of the dot value of the partial color portion is close to the value of the original density value. If the dot value of the partial color portion is deeper than the original density, the color version may be reduced, and if the gray color is cold, the C version may be reduced. It achieves a gray balance and reduces the gray tone. Second, if the partial dot value of the color cast is lighter than the original, if it needs to be deepened, the opposite color can be deepened. If the gray is purple, the Y version can be deepened, which achieves both gray balance and gray deepening.

3 ink tone correction: First, there are layers in the dark tone and black, the dark curve segment tool of the layer curve should be used, and the neutral black dot value ratio should be used to correct the deviation; second, there is no level in the dark tone and black tone, then the color correction can be selected. The black tool is correcting.

4 color part correction: color correction, using Photoshop software to select the Y, M, C, R, G, B hue of the color correction tool for rectification processing, the correction should be based on the saturation of the color, such as green partial green , not bright, is yellow or reduced cyan, if the yellow dot value has reached 95%, and cyan is 90%, then the cyan should be reduced to 80%. If the yellow is 85% and the cyan is 80%, the yellow should be darkened to 95%.

Note: When using the color correction tool to correct the deviation, it is very sensitive to the saturation color, the color correction, the dark color, the school color is slow, if the color correction is large, it must be separately checked out, otherwise it will affect the same color system. The change in color.

9. Black tone processing

The current gravure packaging color image reproduction, how to make good use of the black version, processing the black version is a topic to improve the quality of gravure products. I have seen that many plate-making companies have not processed many black products, not only many garbage products, but also caused printing. Many difficulties, emergency needs to be improved. The author studied in the long-term production practice, summed up the methods and essentials for dealing with the black version. After the promotion and application of some plate-making companies, the product quality was improved immediately, and the printing was printed and praised by customers.

(1) The originals based on color should be based on the three primary colors, and the black version is a short-ordered skeleton. The black tone only serves as a spiritual outline.

(2) Some originals with bright and medium-tone colors, with few gray and dark adjustments, and no black marks on the bags, do not use black plates, and use three primary color plates. If there is a black mark such as a black mark, the color map can be plated with three primary colors, and the black version is exclusively used for black characters, thus solving the printing contradiction between the black portion of the dark portion of the image and the black word outside the image during printing, and the printing can be guaranteed. The precision and blackness of the black characters can make the dark part of the color picture not appear dark and get the best of both worlds.

Processing method: the light and dark levels in the color, using a complementary color instead of the black version. Such as (A) the shadow and neck part of the character's face, the normal four-color configuration has 10%~15% of the black version of the small dot, the printed skin looks grainy, the author takes the black version off, put 10%~15% black The version of the dot value is copied to the green version, and the printed facial shadow and neck skin color are smooth and delicate, and the quality is obviously improved; (B) the green bright tone layer replaces the black color with the complementary color, which is excellent. For example, the green bright mid-tone part, the original dot value M color version is 23%, the K version is 20%, the 20% K version is removed, and the calculation is copied to the M color version, that is, the M color version is 43%, so the green is bright, the level is rich, and it looks delicate and not rough.

(3) Some black-based manuscripts, such as “black sesame paste” bags, use the long-order black-and-white version (GCR) process, which can fully utilize the black version to express the layered texture of “black sesame paste”. It can guarantee black stability and no color cast during printing. The author made a series of more than 10 kinds of "black sesame paste" packaging products in a plate making company, using GCR long-order blackening process, the set value is: (A) the level of highlights, K7% ~ 8%, C4 %, M3%, Y3% (C, M, Y can not be transferred when printing, in fact only black version of small outlets, C, M, Y so put 4%, 3%, 3%, mainly high light level There is continuous transition); (B) dark adjustment part, K90%, partial deepest 95%, C75%, M72%, Y72%, the printing effect is excellent, the customer is quite satisfied.

(4) Because the black silent particles are thicker, and the electric engraving uses a high network cable to ensure the accuracy of the small black characters, the dots are more enlarged during printing, and the average medium and low speed printing presses are almost 80% or more. And paste. Therefore, the black version of the dark part of the image should master two essentials: one is the black version of the dark part, which must be consciously opened; the second is that the black quantity cannot be set too deep, the best is 70% ±5%, so that it can be drawn away from the black text outside the figure, so that the black characters can be printed deep during printing, and the image darkness can maintain the level.

(5) Pay attention to the difference between the black and black objects of the object. The black shadow of the special shadow can not be deep. To maintain the level, the black version of the black object can be deeper, and the local black can reach about 80%, making the black object deep. . Many operators often treat the shadow black of the object as a black object, and set the black version to be deep, which causes the printed product to be dark and dark.

10. Handling of facial skin color

The facial skin color is the most difficult technique to deal with in the reproduction process. Because the skin color is the most sensitive, most familiar, most noticeable, even if the skin color of the printed product is slightly color cast, it will be unpleasant. Therefore, dealing with the facial skin color of the characters is the crown of plate making and printing technology pursued by the plate making company and the electric sub-coloring personnel.

At present, there are two types of portrait photographic manuscripts for gravure packaging products: one is a small-sized cartoon portrait photo and an advertisement portrait photo of a packaged product; the second type is a large-sized poster, a calendar, and other close-up photographs of a half-length photograph, which is processed. The essentials are as follows:

(1) Cartoons and advertising portrait photo processing essentials:

1 guiding ideas. A. First of all, the overall effect of the skin color is emphasized, so that the tone of the skin color is accurate, so that it conforms to the characteristics of the skin color of the character, and only requires to catch up with the color effect of the color provided by the customer, and does not have to emphasize the color change of various parts of the facial skin color; Emphasize that the skin color is saturated and bright, that is, on the one hand, the saturation of the main color version of Y and M is in the range of 10% to 35%. On the other hand, the content of the opposite color C version should be accurate, generally not below 20% of the M color version. C color, which highlights the overall bright and bright complexion, refreshing and pleasing visual effects. If you want to put a small version of the C version that can be transferred, then the Y and M colors must reach the ratio of the dot values that can suppress the C color version.

2 handling essentials. A. The high-gloss skin color should be separated from the extremely high light and white paper. The minimum dot size of the Y and M main color plates should be adjusted to the minimum dot value above which the printing can be transferred, generally a minimum of 8% to 10%, so that the high-gloss skin color is full, and the second is to create conditions for printing out small dots. . B. Dark skin color, if the Y, M main color version exceeds 80%, then the adjustment must be controlled below 80%, then the adjustment must be controlled below 80%, to be separated from the red in the field. Because one is more than 80% of the gravure dots expand in a straight line; the second is that most of the discs now have dark facial adjustments, neck shadows, nostrils, and dark parts of the ears are heavily reddish, Y and M colors are above 85%, and some even reach About 90%, and C color is very small, only 5% ~ 10%, can not hold Y, M color, resulting in printed parts of these parts of the skin color is very reddish. Therefore, to Y, M main color, especially the M color version, use the lasso tool to separate the reddish parts separately, adjust the light to 75% ~ 78%, and deepen the C version to about 25%. This makes the darkness of the dark part calm and stable, and creates favorable conditions for the printing of the red foot. C. Adjust the skin tone to the best visual brightness. The color of the skin in most discs is very large and undulating, some exposure transitions, and the skin tone is weak, which should be adjusted deeper. Some are underexposed, and the skin color is dark and dark. It should be adjusted to reduce the lightness. It should be close to the best visual brightness, giving a comfortable and pleasant visual effect.

(2) The handling essentials of portraits, calendars, and other portraits:

This kind of portrait photography is a high-end product in gravure plate making. It should make full use of the combination of gravure high-tech plate making technology and art for fine processing and artistic processing.

1 guiding ideas. "It should be based on the hope of skin color, and the perfect reproduction of the actual skin color, the original skin color and the desired skin color." Emphasizing the reproduction of portraits, it is necessary to reproduce the vivid character of the human skin color, and to express the skin color effect desired by people. It is necessary to highlight the characteristics of photography art, reproduce the relationship between light, matter and shadow, and according to facial structure and color. The law of light and shadow changes, showing the three-dimensional feeling of the face and the relationship between cold and warm.

2 Master the law of color expression of facial subject. Facial skin color can not be understood as a simple different shades of flesh-colored performance, but there are subtle differences between the various parts, generally with five tonal color shades.

A. Highlight color: should be close to the light source color, generally a neutral white bright color;

B. Inherent color: the most normal color of the skin itself;

C. Intermediate color: at the junction of the shadows, the light gradually moves to the middle part of the dark part, and the hue is generally improved by the natural color, and the faded shadow color is also the normal color of the skin itself.

D. Shadow color: It is located on the entire dark side, and the light reflected by the ambient color is the largest, and the color is cold.

E. Reflective color: Located in the shadow, the color is affected by the reflected light of the adjacent object.

The color change of the above five tones is the basic law of the color to express the three-dimensionality of the face. This law tells us the following four points:

(A) The color of the highlight is the skin color plus the light source color;

(B) The shade color is the skin color plus the ambient color;

(D) The true skin color is expressed in the intrinsic color and the middle color.

In summary, the level of all visible colors of the face is caused by the light according to different facial shapes. The common color change is very scientific.

3 Master the color change law produced by the three major parts of the face.

A. forehead part. The forehead is a part of the face that is prominent. It is a part of the face with a large area. Because it is prominent, the light is brighter and the muscles of the forehead are less, so its color is slightly yellowish and pale yellow.

B. cheek part. The cheek is the largest part of the area, and the structure is complicated. Because the muscles here are full and the muscles are covered with capillaries, the color is more rosy and full.

C. up and down the part. Part of the upper jaw is the same as the flesh color system, because it is smaller than the forehead and cheeks, and is in the lower part of the face. The hue is dark, which is the intrinsic color of the skin color and the middle color part.

The general proportional relationship between the Y and M color plate dot value configurations of the above three parts of the face (see Table 2).

Forehead Denomination Lower amount

Y 30% 35% 30%

M 25% 40% 30%

Of course, this refers to the configuration relationship of a specific person in a specific environment, and then configure an appropriate C color change to obtain a more varied skin color.

General beauty, children's skin color.

(A) Forehead part Y>M, 2%~3%, individual pink baby's skin color and white, can also be M>Y;

(B) facial paralysis part, M>Y5%~15%, thus fully expressing The beauty of the two red cheeks.

In summary, according to the color changes produced by the three major parts of the face, the proportional relationship between the Y and M color versions is basically this law, which is stable. As for the specific values, the characteristics of the characters and the color density of the original are determined. And set.

4 master the law of the contrast between the three primary colors of the face high light tone. Mastering the contrast strength of the three primary color versions of the face high light tone, fully demonstrating the rich color level changes of the high light tone, is one of the key technologies for making high-quality character skin color. According to the law of facial light and color change, the contrast strength of the three primary color versions is:

A. The Y color has the strongest contrast. Therefore, it is necessary to adjust the contrast of the Y color to a larger extent, and to use the Y color to express the hierarchical texture and color change of the high light tone. Generally, the Y-color version has a coarser grain size, and since the Y color is weak in color value, it is superimposed by a delicate red color, so there is no influence.

B. The contrast of C color is the weakest, and the fine facial skin color treatment, high light tone should put a minimum dot value that can be transferred by printing, because according to the principle of color light, the stronger the light, the colder the color, and the blue-violet color. Therefore, the C color is used to express the color change of the high light tone, which adds beauty to the skin color.

C. The brightness of the M color, the contrast is between Y and C, the contrast of the high light level is weaker than the Y color, and the color is stronger than the C color. The processing of the M color version needs to be rich in layers, softly coordinated, and fine in grain.

Typical gravure character color tone high-tone three primary color dot value is configured as Y10%, M12%, C5% or Y13%, M15%, C6%.

Practice has proved that the high light tone that is processed according to the contrast strength of the above three primary colors is extremely exciting and pleasant.

Fifth, Judging the quality of the electrogram and the color

From the screen, digital proofs, gravure ink proofs and printed product samples, you can analyze and judge the quality of the electric score and color from 10 aspects.

1. First of all, from the overall color tone of the screen, whether it conforms to the color tone of the customer's sample, 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 picture, especially the color of the person, conforms to the true color of the objective object and the color desired by the people and the color required by the customer. Does it highlight the attributes of the product and emphasize the saturation of the color.

3. In the middle of the object, is the basic color of the dark high area rich in levels, whether there is a leveling phenomenon, the highlight area, and the basic color of the light tone area of the bright area is full? There is no loss of peace and light feeling.

4. What is the bright color of the highlights? Is it beautiful? Is it saturated? Is there a feeling of darkness and oldness?

5. Whether the wind point gradation contrast of the electric part map meets the requirements of the gravure printing process, whether there is a phenomenon that the contrast is too large or too flat. That is, whether the high-gloss white of the layer needs a layered texture, whether there is loss or flatness. Is the minimum dot value of OPP film printing more than 5%~7%, and is it far from the high gloss and white paper? Does the dark tone part have a level, is there a leveling phenomenon? Is the maximum dot value of the C version in the deepest part of the dark adjustment controlled at 90%~93%? Is the dark flesh of the person's face red? It is controlled at 80% or less, and whether it is separated from the deep original color in the field.

6. Is the color level of the main part of the picture rich? Is the color density set within the optimal visual brightness range? Is there a ill or too dark ill?

7. Object color, highlight to bright, bright to middle, middle to dark to connect naturally? Does the hue continue to transition? Whether there is a hard mouth or a disjointed and rough particles.

8. Whether the white, gray, and black in the image are restored accurately, with or without color cast, and color.

9. The outline of the image is clear, the texture is clear, and the particles are fine.

10. Finally, observe the whole picture, the subject image is clear, the color is bright, the layers are distinct, the texture is clear, the particles are delicate, giving a refreshing and pleasing strong color appeal.