This article will explain the application of color science in printing from the aspects of printing chromatographic production, printing hue measurement and spot color ink blending.
1 Using color science to produce printing chromatography
Throughout the color reproduction process, it has undergone three processes of color analysis, color transfer, and color combination. The correctness of color change control in each process is directly related to the final quality of the printed matter, so a color standard, that is, printing chromatography, is required to regulate various hue in the printing process. Shanghai Printing and Printing Chromatography uses three primary colors of yellow, magenta, cyan and black. It is mixed and stacked in different proportions or dots to form a photo album of various color patterns for people to design, copy and ink. Check and use.
Four-color chromatography uses yellow, magenta, cyan, and black four-color inks with different dot area percentages (usually only 0, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% eleven dot grades, or 5% aliquots of dot grade) overlay overlays, arranged in a certain order, it has the same process for electronic color separation, proofing and printing Important reference and guidance. The spot color in printing is a color ink that has been mixed, and the color is not directly related to Y, M, C, and K. Therefore, a set of standard primary color inks is first defined, and various kinds of mixing colors are produced according to different mixing ratios. The color chromaticity sample, each color sample is marked with a scalar indicating the mixing ratio of the primary colors, so that people can use the three primary color inks to blend the color colors of various colors. This is the spot color chromatography.
At present, Pantone color matching chromatography of American PANTONE is widely used in the world. However, printing chromatography uses color to indicate color. Its production is usually affected by many factors such as ink, paper, printing process and equipment. Therefore, the printing unit should make its own special according to the raw materials, production process and equipment conditions used by the factory. Printed chromatography.
2 using color to measure color and color difference
The color measurement in color printing can be roughly divided into three types: contrast visual method, density measurement method and color measurement method.
The color measurement is measured by the contrast visual method in the printing process, mainly by an experienced operator who evaluates the color of the original, the signal strip, and the printed sheet by a comparison visual method with reference to the standard color ratio. Due to the influence of the observer's own physiological and psychological factors, the accuracy of the comparison visual method is relatively poor. However, because it does not need to be equipped with fine measuring instruments, it is widely used in general copying work.
Densitometry is a method of measuring the tone and color of a color using optical density values. In the color printing process, the density value can well reflect the proportional relationship and superposition performance of the three primary color inks, and the detection equipment is simple, so it is widely used. However, the optical density is used as the monitoring and measuring method of the printing process. The size of each monochromatic ink can only be obtained from the control strip, and the information of the color error cannot be directly obtained from the image, so that it is difficult to communicate with the printing customer, which is inconvenient. Density measurement is precisely controlled, so density measurement is just an indirect method of color measurement.
The chromaticity measurement method is based on the principle of colorimetry, which uses the color of the important part of the printed image as a monitoring point, directly measures the tristimulus value of the color, and acquires the color measurement method of the color chromaticity information. The method can accurately express the color difference between the standard proof and the sample to be tested and the required proximity, without additional check or control strip. However, it has not been promoted and popularized at present, mainly because the instrument is expensive and has high color theory requirements for users. As a large-scale cigarette printing company, most of our products involve spot color printing. Due to the good use of color measurement to control chromatic aberration, we have rarely complained about customers in color for several years.
In the color printing copy work, not only to understand the three attributes of the color, but also to understand the difference between the colors, in order to compare and distinguish the color, which is the color difference. The unit of color difference is NBS, which is an abbreviation of the US National Bureau of Standards. At present, the color measurement standard commonly used in the world is the CIE1976Lab uniform color space, which was proposed by the Canadian Weizesky at the 18th CIE Conference in 1975. Where L is the psychological brightness, a and b are the psychological chromaticity, and the color difference is represented by △E. When a is positive, it means reddish, when it is negative, it means greenish; when b is positive, when b is positive, it means Yellowish, when it is negative, it means bluish; when L is positive, it means light color, otherwise it is darker. The color difference ΔE is generally less than 3, and the chromatic aberration is not very large, but it is also affected by the deep, light color and the printing material.
3 use color science to match spot color ink
Ink is a coloring substance for printed matter. It is a mixture of coloring materials, binders, fillers and cosolvents. It is a complex colloid. Ink blending refers to the process of blending one or more inks together with a certain auxiliary material to meet the printing and color requirements. Any color printed in Shanghai can be obtained by mixing different primary colors in different proportions.
3.1 The law of ink color matching should follow
(1) The deployment of the spot color ink should be carried out under the standard light source D65. If it is during the day, it can be carried out in the sunny north window.
(2) The three primary color inks are mixed in equal amounts to approximate black. If you add different proportions of white ink or thinner, you will get different grades of gray ink.
(3) The three primary color inks are mixed in different ratios to obtain inter-color or complex color of different hue.
(4) The two primary colors of the ink are mixed in equal amounts to obtain the inter-color; when mixed in different proportions, the inter-colors of different hue can be obtained.
(5) The more color hue types used in color matching, the worse the brightness is. The black ink is added to any hue ink, and the brightness value is reduced. When white ink is added, the brightness is increased.
(6) Pay attention to the influence of the paper used, the color sequence of the printing, the color of the illumination source on the ink color and the color before and after the blotting.
(7) The complementary color can be used to correct the color shift, but it can only be performed when the brightness value of the ink is high.
(8) Try to use less original inks of different varieties to reduce the complementary color.
(9) Pay attention to the influence of ink viscosity on hue.
(10) Before the more complex spot color is inked, a small amount of test can be firstly determined, the ratio is determined, and then the amount of ink used is dispensed to avoid waste.
3.2 Dark ink blending
Only use three primary colors or intermediate color inks, without any dilution agent for ink preparation, collectively referred to as dark ink blending. There are several steps in the preparation of dark inks:
(1) Determine which primary colors are included in the original color sample and discharge the main color, the auxiliary color order, and the approximate proportion of each color ink.
(2) According to the ink area of ​​the printed matter, ink tinting strength, plate depth, paper properties, ink viscosity, printing quantity and other factors, determine the number of blending.
(3) According to the proportion of blending, add ink in the order of large to small. First weigh the main primary color with the most content, then weigh the auxiliary color with less content, then add the secondary color ink to the primary color ink several times and mix it evenly.
(4) After comparing the colorimetric and adjusting the proportional relationship of the three primary colors, after conforming to the original, the printing suitability is adjusted by the printing aid.
(5) Record the proportional relationship of the primary color components used in order to ensure the consistency of the ink color when the reprinting or the amount of ink is insufficient.
This article will explain the application of color science in printing from the aspects of printing chromatographic production, printing hue measurement and spot color ink blending.
1 Using color science to produce printing chromatography
Throughout the color reproduction process, it has undergone three processes of color analysis, color transfer, and color combination. The correctness of color change control in each process is directly related to the final quality of the printed matter, so a color standard, that is, printing chromatography, is required to regulate various hue in the printing process. Shanghai Printing and Printing Chromatography uses three primary colors of yellow, magenta, cyan and black. It is mixed and stacked in different proportions or dots to form a photo album of various color patterns for people to design, copy and ink. Check and use.
Four-color chromatography uses yellow, magenta, cyan, and black four-color inks with different dot area percentages (usually only 0, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% eleven dot grades, or 5% aliquots of dot grade) overlay overlays, arranged in a certain order, it has the same process for electronic color separation, proofing and printing Important reference and guidance. The spot color in printing is a color ink that has been mixed, and the color is not directly related to Y, M, C, and K. Therefore, a set of standard primary color inks is first defined, and various kinds of mixing colors are produced according to different mixing ratios. The color chromaticity sample, each color sample is marked with a scalar indicating the mixing ratio of the primary colors, so that people can use the three primary color inks to blend the color colors of various colors. This is the spot color chromatography.
At present, Pantone color matching chromatography of American PANTONE is widely used in the world. However, printing chromatography uses color to indicate color. Its production is usually affected by many factors such as ink, paper, printing process and equipment. Therefore, the printing unit should make its own special according to the raw materials, production process and equipment conditions used by the factory. Printed chromatography.
2 using color to measure color and color difference
The color measurement in color printing can be roughly divided into three types: contrast visual method, density measurement method and color measurement method.
The color measurement is measured by the contrast visual method in the printing process, mainly by an experienced operator who evaluates the color of the original, the signal strip, and the printed sheet by a comparison visual method with reference to the standard color ratio. Due to the influence of the observer's own physiological and psychological factors, the accuracy of the comparison visual method is relatively poor. However, because it does not need to be equipped with fine measuring instruments, it is widely used in general copying work.
Densitometry is a method of measuring the tone and color of a color using optical density values. In the color printing process, the density value can well reflect the proportional relationship and superposition performance of the three primary color inks, and the detection equipment is simple, so it is widely used. However, the optical density is used as the monitoring and measuring method of the printing process. The size of each monochromatic ink can only be obtained from the control strip, and the information of the color error cannot be directly obtained from the image, so that it is difficult to communicate with the printing customer, which is inconvenient. Density measurement is precisely controlled, so density measurement is just an indirect method of color measurement.
The chromaticity measurement method is based on the principle of colorimetry, which uses the color of the important part of the printed image as a monitoring point, directly measures the tristimulus value of the color, and acquires the color measurement method of the color chromaticity information. The method can accurately express the color difference between the standard proof and the sample to be tested and the required proximity, without additional check or control strip. However, it has not been promoted and popularized at present, mainly because the instrument is expensive and has high color theory requirements for users. As a large-scale cigarette printing company, most of our products involve spot color printing. Due to the good use of color measurement to control chromatic aberration, we have rarely complained about customers in color for several years.
In the color printing copy work, not only to understand the three attributes of the color, but also to understand the difference between the colors, in order to compare and distinguish the color, which is the color difference. The unit of color difference is NBS, which is an abbreviation of the US National Bureau of Standards. At present, the color measurement standard commonly used in the world is the CIE1976Lab uniform color space, which was proposed by the Canadian Weizesky at the 18th CIE Conference in 1975. Where L is the psychological brightness, a and b are the psychological chromaticity, and the color difference is represented by △E. When a is positive, it means reddish, when it is negative, it means greenish; when b is positive, when b is positive, it means Yellowish, when it is negative, it means bluish; when L is positive, it means light color, otherwise it is darker. The color difference ΔE is generally less than 3, and the chromatic aberration is not very large, but it is also affected by the deep, light color and the printing material.
3 use color science to match spot color ink
Ink is a coloring substance for printed matter. It is a mixture of coloring materials, binders, fillers and cosolvents. It is a complex colloid. Ink blending refers to the process of blending one or more inks together with a certain auxiliary material to meet the printing and color requirements. Any color printed in Shanghai can be obtained by mixing different primary colors in different proportions.
3.1 The law of ink color matching should follow
(1) The deployment of the spot color ink should be carried out under the standard light source D65. If it is during the day, it can be carried out in the sunny north window.
(2) The three primary color inks are mixed in equal amounts to approximate black. If you add different proportions of white ink or thinner, you will get different grades of gray ink.
(3) The three primary color inks are mixed in different ratios to obtain inter-color or complex color of different hue.
(4) The two primary colors of the ink are mixed in equal amounts to obtain the inter-color; when mixed in different proportions, the inter-colors of different hue can be obtained.
(5) The more color hue types used in color matching, the worse the brightness is. The black ink is added to any hue ink, and the brightness value is reduced. When white ink is added, the brightness is increased.
(6) Pay attention to the influence of the paper used, the color sequence of the printing, the color of the illumination source on the ink color and the color before and after the blotting.
(7) The complementary color can be used to correct the color shift, but it can only be performed when the brightness value of the ink is high.
(8) Try to use less original inks of different varieties to reduce the complementary color.
(9) Pay attention to the influence of ink viscosity on hue.
(10) Before the more complex spot color is inked, a small amount of test can be firstly determined, the ratio is determined, and then the amount of ink used is dispensed to avoid waste.
3.2 Dark ink blending
Only use three primary colors or intermediate color inks, without any dilution agent for ink preparation, collectively referred to as dark ink blending. There are several steps in the preparation of dark inks:
(1) Determine which primary colors are included in the original color sample and discharge the main color, the auxiliary color order, and the approximate proportion of each color ink.
(2) According to the ink area of ​​the printed matter, ink tinting strength, plate depth, paper properties, ink viscosity, printing quantity and other factors, determine the number of blending.
(3) According to the proportion of blending, add ink in the order of large to small. First weigh the main primary color with the most content, then weigh the auxiliary color with less content, then add the secondary color ink to the primary color ink several times and mix it evenly.
(4) After comparing the colorimetric and adjusting the proportional relationship of the three primary colors, after conforming to the original, the printing suitability is adjusted by the printing aid.
(5) Record the proportional relationship of the primary color components used in order to ensure the consistency of the ink color when the reprinting or the amount of ink is insufficient.
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