The most popular printing system produces high-qua

2022-08-02
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The printing system produces high-quality images (III)

handle the normal relationship between colors

at present, the color processing of some color printing materials is very messy, and the original color cannot be restored. Many customers (including artists such as painters and photographers) are not very satisfied, A photographer also wrote an article: "In color printing, it is often seen that in order to make the picture colorful, regardless of the normal relationship between colors, regardless of the specific position of a specific color in the picture, they are all adjusted to be very pure. Although it is colorful, the whole picture looks messy.

at present, most operators do not master the standardized scanning color separation of restoring the original and lack the artistic understanding of color. They just look at the color of the display screen, It is caused by subjective and random adjustment, and often the amount of adjustment is too large. The solution is:

1 It is the most important basic work to do a good job in standardized and data-based color management. Even if software automatic color management is adopted, it must have this foundation to make the whole process have a stable environment. The method steps are as follows:

(I) first, formulate the process technical parameters and quality standards for post process Phototypesetting, printing and proofing, and make them stable

(II) the standard gray scale, color code and original are used for color restoration test, and a set of gray balance parameter sets are established to ensure the gray and multicolor restoration in the original

(III) based on the input gray balance, establish the color calibration amount for color correction to achieve the restoration of R, y, G, C, B and m, so as to ensure the restoration of the original color. After doing the above work, when scanning and color separation, as long as the correct black and white field settings are used, the tone of the original can be restored without or little need for post-processing. Instead, Photoshop software tools are used to adjust some defects of the original only to meet the requirements of customers

2. Make full use of the scanner to obtain the best image. At present, the image scanning and color separation operation must get rid of a misunderstanding, that is, the high-end professional scanner and electric extension are regarded as simple input devices, and their powerful professional functions are not used or used well. Instead, the black-and-white field calibration, level adjustment, color correction and sharpness emphasis are all adjusted by Photoshop software tools, which not only takes a long time to adjust, but also has unstable quality, Often one person adjusts one sample, or even one sample at a time. There are many kinds of colors, and because there is only a small amount of color hierarchy information in the scanned color separation image, Photoshop software tools can not call up a better color hierarchy. What's more, the artistic conception and subtle color level changes in image art such as painting and photography cannot be adjusted

many excellent peers have realized in practice that "in order to finally print a good product, all the information required for the product must be obtained from the original at the beginning of scanning. This is like recording good music. The microphone should be good first, otherwise the quality is impossible."

nowadays, many good printing units engage in digital color management and adopt the "standardized scanning and color separation method to restore the original" to achieve the effect of restoring the original quickly and well. For this reason, the unit stipulates that the customer requires to restore the original, scan the color separated image, and do not carry out post-processing. If the quality is poor, it will be re scanned. During the production of apple computer, the pictures scanned by the scanner and the electronic extension can only be repaired, cut or treated with special effects, and the picture level, color and definition cannot be adjusted, nor enlarged or reduced. This is the only way to improve the quality and efficiency

3. The four essentials of dealing with color. When adjusting defects such as insufficient local color saturation of the original, you should master the following four points:

(I) do not add or subtract too much color. First, the basic color addition should not be too large, and the levels in the basic color should be maintained, and the levels should not be merged due to excessive color addition; Second, the amount of opposite color correction should not be too large, and the relationship between light and shade should be maintained in the color, so that the color can be simplified due to excessive opposite color correction

(II) maintain the relationship between the color quantity of the color and the ordinary light quantity. When adjusting a color, the color quantity of the bright part shall not exceed the color quantity of the middle note part, and the color quantity of the middle note part shall not exceed the color quantity of the dark part. Maintain the relationship between the color quantity of the color and the light quantity grade. At present, some printing materials adjust the colors of the bright parts too deeply and too heavily, and deal with the colors of the dark parts too bright and too bright, thus losing the normal relationship between colors and giving people an uncomfortable feeling

(III) master the spatial distance change law of color. In terms of chromatics, due to the influence of large space and better use of material gas medium, objects at different distances will have different changes in shape and color. The principle of spatial perspective is that the object is near, far and small, while the object that is near is clear, the object that is far is fuzzy, the color perception that is near is strong, and the object that is far is weak, which is the result of color spatial perspective. Therefore, when adjusting a certain color, it is necessary to master the change law of color expression space distance, which is warm in the near and cold in the far; Near pure, far gray; The near contrast is bright, the far contrast is fuzzy, the near contrast is strong, and the far contrast is weak. For example, in a landscape album, the operator added some yellow to the purple and blue of the distant mountains and turned them into turquoise green. As a result, the color change of the spatial distance was completely distorted. The customer shook his head and said that it did not conform to the original color. As a result, it was required to scan and print again. It is proved by practice that it is important to adjust the color according to the change law of the space distance of the color in the test method of the leaf spring bench fatigue tester

(IV) master the change law of color temperature and temperature. In the natural scenery photographed by color photography, we find that the color of the light receiving surface of the object is inseparable from the change of the light source color, and the color of the dark surface is closely related to the change of the surrounding environment color. Therefore, when carrying out color adjustment, it is necessary to master the change law of this kind of color. Two issues should be noted. First, the light receiving surface of the object image has three parts: high light, bright surface and middle note surface. The hue of the bright surface is mainly the combination of light source color and solid color. The temperature of the hue is transferred by the temperature of the light source color; The color of the highlight part is generally the hue and chromaticity of the light source color; The light received by the middle note surface of the object image is not direct light, but side light, which is more complex and rich in hue and chromaticity. Its hue is the combination of light source complementary color, solid color and environment color, and its color sense is mainly solid color. Second, the hue of the dark side of the object image is mainly the mixture of the environment color and the inherent hue. The temperature of the hue is transferred by the temperature of the environment color, and the color of the dark part always has the complementary color tendency of the light source color. Therefore, we should pay attention to the dark color is not the deepening and darkening of solid color. The relationship between cold and warm colors in photographic images can only be satisfied by using the standardized scanning color separation method to restore the original. To deal with the skin color of the characters, there are many problems in the reproduction quality of the close shot bust pictures in many journals, magazines, pictorials, picture albums and some advertisements, some of which are of poor quality. For example:

(1) some skin colors are seriously distorted, and some face colors are orange, black tea, or even vegetable green, gray black

(2) some skin colors are rough, stiff and disjointed, and there is no continuous and excessive tone among bright, medium and dark tones, which seems to lack the beauty of changing curves; Due to the use of GCR process, the dark part is reversed. The yellow and red versions are light and become just a very deep black version

(3) some skin colors are reversed in the dark due to the GCRI process. The yellow and red versions are light, and become just a very dark black version

(4) it is obvious that some skin colors are wrong in color correction. Due to excessive color correction of the green version, the eye flesh and tooth flesh are corrected to red flesh color, and a circle of black tea edges are exposed at the junction between the hair edge and the skin color

in addition to some original factors, the above problems are mainly caused by improper scanning and color separation parameter settings and color processing. The general solution is:

1 Set the tone of your skin tone. When scanning and color separation of characters, regardless of the original, it should be processed according to the characteristics of the skin color of various characters. First, determine the tone of the skin color based on their age, gender, occupation, origin, nationality and other characteristics. For example, the skin color of children should be white, delicate, delicate and ruddy. "Beauty photo" refers to the skin color after makeup. The skin is white and ruddy, the color is boastful, and the changes are rich. If the original is biased, it should be corrected according to the character's skin color characteristics. Only if the tone is correct, there will be no major distortion

2. Control dark skin color without redness. The dark tone skin color of most originals tends to be reddish brown. After the black field setting, the Y and M color versions tend to be darker, and the dot value reaches about 85%, sometimes 90%. The c-color version is sensitive to black tea color correction, and is often over calibrated. Therefore, for dark tone skin with large area, first, pay attention to control the Y and M versions below 80%, which is generally%. Because 80% is a point jump area, the printing point is easy to increase; Second, the color C version should keep up with the standard color correction. It should be slightly deepened on the basis of the standard color correction. At the same time, the gradient of the K version should be slightly extended to make up for the deficiency of the C version. Generally, if the M and Y color versions are 75%-78%, the color C version should be 30% and the K version should be about 25%, so as to make the dark skin calm

3. Regulate the shade density and control the color of middle note tone

(I) smoothing film: most of the face is in bright and middle note, and its color density conversion to point value is mostly 30%-45%, which is ideal, and the normal set skin color restoration is better

(II) side backlight film: half of the face is in the backlight part, and the middle note density gradually moves to the darker part. The key technology here is to control the Y and M color plates on the forehead of the middle note. The forehead skin color density of some side backlights is at 0 95, the converted point value is 51%-53%. Since 50% is another jumping area of offset printing point, the printing point increases the most. Therefore, we should pay attention to lighten the point values of Y and M versions to 45%-48% to avoid the jumping area of this point and make the forehead bright and yellow

(III) backlight film: most of the face is backlight, with high density and dark skin color. With the forehead as the control point, the color density is converted into point value, and the Y and M color plates are between 60%-70%. Therefore, first of all, the lightening level curve should be selected to scan the color separation, or the middle note part of the Photoshop level curve after scanning, and the three color plate should be lightened (lightened) by 5%. In this way, not only the color density of the printed matter conforms to the visual effect, but also the printed matter points should be increased. 4. master the continuous excessive tone of skin color. When setting the gradient and adjusting with the hierarchical curve, it should be understood that there should be a continuous and excessive tone from the bright part to the middle note part to the dark part of the face color, and the tone of the m-color version should be soft and harmonious

5. Correct selection of virtual light filter. Theoretically, what color light should be selected for the virtual light filter should be based on the clarity of the main tone of the original. The green (g) filter emphasizes the clarity of the warm tone. Generally, the default values of scanners and electrical extensions are green (g), and some are c=c, m=m, y=y, k=y. Some of the Y, m, C and K color versions are g (5:5) mixed colors. The skin color should be soft and the hair should be clear, so it is better to choose red (R) filter with different effects to meet the needs of different industries. In a word, we have deep knowledge and experience in image scanning and production in prepress system, and the quality of film output is directly

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