Computer boardmaking, or color desktop system making, is a rapid development method in recent years. Compared with traditional electronic color separation and manual patching, computerized patterning is characterized by its combination of graphic and textual, creative design, and diverse functions, and has been significantly shortened. The plate making cycle has enriched the page image and saved raw and auxiliary materials. At the same time, the color tactical surface system is flexible in configuration, easy to upgrade, and can not only output color separation films, but also can output color slides, light boxes, decorative materials, printing plates, multimedia CDs, and even directly through the network through various output devices. publishing. Many electronic color separation machines can output high-quality graphic page color separations directly through high-end networking. However, it has also been found in practice that the effects of computer-based plate making are very different, and they can be summed up in the following reasons:
1. System equipment performance \ precision (such as scanners, film photosetters, etc.);
2. The quality and level of operators;
3. The standardization of quality management.
This article focuses on the standardization of quality management, and puts forward some principle requirements for the standardization of computer scanning color separation, processing, output, drying and proofing, in order to improve the quality and efficiency of computer plate making as a whole.
one. The process of computer-based plate-making is a complex system engineering from manuscripts to replicas. Whether the replicas can be relatively restored to manuscripts is constrained by various factors such as environmental conditions, raw materials, equipment performance, process conditions, and operation levels. Therefore, the principle of process management is to change from color separation to proofing, and stabilize all factors that can be stable. Remember that all process conditions are not required to be the best, but they are relatively stable. Only by restoring and copying relative to the original document can we talk about making up for defects and artistic processing on the original.
The main content of process management is obtained under the condition that the system hardware and software work normally, according to the raw materials used for printing or proofing (paper, ink, plate, etc.) and printability (ink volume, pressure, ink balance, etc.) Process data to determine the following copy elements of the system.
- Black and white field adjustment range;
- Grey balance curve;
- Fixed level curves and black version curves for different manuscript types;
- The color saturation of different original types;
- The maximum total ink volume for different paper types;
- The dot gain rate of printing or proofing;
- The principle of clarity;
- Specification for printing and proofing.
1. Black and white field tone range: This is an important indicator of image quality. The larger the range of gradation, the greater the image contrast, the larger the gamut of copying, the better the visual effect, and the stronger the three-dimensional effect. However, the range of adjustment is limited by the conditions of the post-process. If the white field dot on the color separation film is too small, it may not be printed on the printing plate. If the dot size is too large, it may become a stencil after printing/proofing. Different printing and proofing procedures have different gradation ranges (ie, the same minimum dot area and maximum dot area). This needs to be determined after careful testing according to actual conditions.
For different manuscripts, the range of tonal adjustments is also slightly different. For example, if you use the landscape tone range of landscape manuscripts as the standard (for example, 2% to 88% for yellow and magenta, and 4% to 94 for cyan) %, black version is 0 ~ 75%), the oil painting manuscript and the color version of the tone range should be wider (such as the width of 2% to 3%); character manuscript tone range to be slightly narrower (such as narrow 3% ~ 5 %); while the Chinese version of the color version of the tone range should be narrower (such as narrow 5% to 7%), but the black version to lengthen 10% to 15%.
2. Gray Balance Curve: In the process of determining the range of tone, at the same time, determine the dot percentage curve of each color separation (yellow, magenta, and cyan) that can guarantee the restoration of the original neutral ash. For example, white field (2% for yellow, magenta, 4% for green), middle tone (39% for yellow, magenta, and 50% for blue), dark field (yellow, magenta, 88%, green 94%). For different post-process conditions, especially the ink hue, the gray balance curve is very different. Whenever major post-process conditions are changed, a new gray balance curve must be confirmed.
3. Fixed level curves and black version curves for different original types: Since the original has transmission and reflection points, the density range of different originals is not the same, and some abnormal originals may be too thin or too thick, so for transmitted originals and reflections The manuscript can be set with 5 fixed-level curves, respectively, corresponding to different levels of curves through different gamma values, to adapt to different density ranges and different thickness of the original. Using the middle tone as the standard value as a fixed-level curve, the other four levels of the curve correspond to the midtones to light up -5%, -10%, and the midtones to increase the weight of +5%, +10% (percentage of the outlets).
Different manuscripts have different black curves. For example, the length of the black version of the landscape manuscript is the standard (for example, 0 to 75%). The black version of the Chinese painting needs to be lengthened (10% to 15%); the black version of the character manuscript It should be shorter (5% to 7% shorter); the black version of watercolors and gouache should be shorter.
4. Different original types correspond to different color saturation settings: In principle, originals with a relatively flat and thin color must be processed with increased color saturation, while thick originals should be reduced in color saturation. Based on the final proofs, set the standard color saturation. For the overall color cast, local color cast can be handled by different color correction methods (Image/Adjust).
5. The maximum total ink amount required for different papers: The total ink volume of imported coated paper is allowed to reach 340%-350%; the total ink volume of domestic coated paper is 320%-330%, and the total ink volume of offset paper is 280%-300 %, and so on.
6. Dot gain ratio (compensation amount) setting for different types of originals: In general computer software, the built-in compensation amount for the dot gain rate is 20% (this is not the actual enlargement rate of the midtone dot, but the relative enlargement rate). According to the practice, the dot enlargement rate mainly depends on the ink characteristics and printability. If the dot gain compensation rate is not corrected for the built-in value, the effect of the image duplication tends to be the result of the middle tone emphasis and dark tone levels. In general, the original dot gain compensation value should be 28% to 32%, and the transmission original should be 24% to 28%.
7. The principle of sharpness emphasizes: In the process of image duplication, the clarity of the final copy is closely related to the clarity of the original document, the magnification ratio, the number of screens to be connected, and whether the sharpness processing is appropriate. Insufficient sharpness processing or improper image processing will result in poorer definition. If sharpness is handled excessively (such as sharpening, false light masking, and excessive edge sharpening), noise and relief will appear. Usually when the computer processes images, whether it is shrinking/enlarging, color space conversion, input/output precision conversion, image compression/decompression, and moiré/smoothing/noise processing, it will directly affect the clarity of the output image. . Therefore, for different manuscripts, different magnifications, sharpening radius, sharpening intensity, and threshold setting must be continuously summed up through practice, and the image should be repeatedly and repeatedly processed as much as possible.
8. Standardization of printing and proofing process 2. Calculation of system management of the executive version The so-called “system management†refers to ensuring the consistency of manuscripts, computer screens, proofing and proofing. In addition to the printing and proofing procedures, the system management includes the following:
1. Input scanner calibration: The purpose of the calibration is to make the image data input by the scanner into the computer, which should basically represent the characteristics of the color document, ie whether it is a translucent document or a reflection document, its reference white field after scanning, neutral gray balance, The basic characteristics such as the level curve, the basic color, and the reverse color can be normally reflected in the image data. Therefore, it is necessary to continuously correct the relevant parameters in the scanning software, so that the output proofing is basically consistent with the original document without using computer image processing software. If the scanner can't be calibrated often, relying on computer software to correct the image data not only takes more hours to deal with the image injury, but also the image effect is difficult to maintain the same.
2. Calibration of the computer screen display: If you can achieve the screen display and the effect of proofing / printing, it can achieve the "What You See Is What You Get" realm. However, due to the fact that there is a large gap between the color gamut displayed by the fluorescent screen and the color gamut of the printed ink, it is impossible to achieve the complete agreement between the two. However, if the screen display is not calibrated, and the operator lacks experience in determining the color separation data, then the effects of the computer processing and the expected effects will be completely different, and the processing results of different workstations will be very different. Regarding the screen calibration method, we described it in "Application of Standard Color Image Data (SCID)" (see "Printing Standardization", 1997, No. 4), that is, using a standard image data independent of the input scan to output component color chips, Under the premise of stable printing and proofing process conditions, proofs are obtained, and then screen calibration software (such as KNOLL software) is used to compare the proofs, and after the color balance, brightness, and Gamma curve are adjusted, the screen display is basically close to proofs.
Here is what we need to explain. Many computer operators often use commercially-available chromatography as a reference to determine color reproduction, but the effect is poor. This is because the various raw materials and processing conditions of this chromatogram are different from those of its own after-processing. The effect of color reproduction cannot be the same. The best way to do this is to use the chromatograms that you need to proof or print after you stabilize the conditions of the post process.
3. Calibration of color printer or digital proofing system: In general, ordinary color printers can rarely be calibrated, often through computer output driver software. If a corresponding printer can be selected for a long time, the output effect is better, otherwise the output effect varies greatly. The digital proofing system itself has calibration software, as long as the digital standard output (system comes with it) or standard image chromatogram (such as SCID standard color image data) is compared with the traditional proofing effect, after adjustment by the calibration software, basic Digital proofing can be consistent with traditional proofing. Regardless of whether the dot structure of the digital proofing system is a conventional amplitude modulation network point or a frequency modulation network point or a continuous tone structure, various indicators such as sexual gray balance, color reproduction, and hierarchical reproduction can be compared with conventional proofing.
4. Calibration of the output image-setter: adjustment of the linearization of the film is performed under the condition that the film and the developing conditions (development time, developing temperature, developer replenishment amount, etc.) are fixed, and the alignment needs to be calibrated. The adjustment of the laser intensity is to ensure that the density on the dichroic plate can reach or exceed the density of the substrate at least 3.5D (or the core density of the dots is 2.5D or more). The software linearization adjustment is to ensure that the actual dot percentage value on the color separation sheet is consistent with the percentage value (tone value) of the CMYK dot displayed on the computer, and the error should be less than ±2%. Check the gradation value of the test ladder on the color separation film every day. If the above error is exceeded, adjust the film linearization.
Third, the operation of computer-based plate management "Operation management" refers to the daily production of job flow management. There are the following basic requirements:
1. "Qi, Qing, Ding" of user's work: That is, the user's manuscript, manuscript, layout should be neat, the user's process requirements should be clear and clear, the user should determine (recognize) the final proof.
The most important thing for Qi is the layout requirements. Normally, there is a difference between formal computer design and creative design. Design workstations often take up a long time and require repeated discussions with users. Under normal circumstances, the design workstations are not networked with the system. You can use disk to exchange files. The average user does not attach much importance to the layout, nor is it standardized. The process requirements are not specific and unclear. The layout changes at random will often cause plate rework, invalid machine times, and significantly reduced efficiency.
Layout design itself is a technical work that embodies the user's design style and level. It often goes through layout design by a professional design company in foreign countries. The original and layout design disks are provided to the platemaking company. At present, China still cannot reach this level, and it needs to gradually train users to improve the user's design level and standard level. For users who are not capable of designing their own layouts, the plate-making company can design layouts for users, but the user’s Layout requirements must be clear and specific.
The user's process requirements include both the layout's own requirements and the technical requirements for images, text, and background. For example, the opener of the page
1. System equipment performance \ precision (such as scanners, film photosetters, etc.);
2. The quality and level of operators;
3. The standardization of quality management.
This article focuses on the standardization of quality management, and puts forward some principle requirements for the standardization of computer scanning color separation, processing, output, drying and proofing, in order to improve the quality and efficiency of computer plate making as a whole.
one. The process of computer-based plate-making is a complex system engineering from manuscripts to replicas. Whether the replicas can be relatively restored to manuscripts is constrained by various factors such as environmental conditions, raw materials, equipment performance, process conditions, and operation levels. Therefore, the principle of process management is to change from color separation to proofing, and stabilize all factors that can be stable. Remember that all process conditions are not required to be the best, but they are relatively stable. Only by restoring and copying relative to the original document can we talk about making up for defects and artistic processing on the original.
The main content of process management is obtained under the condition that the system hardware and software work normally, according to the raw materials used for printing or proofing (paper, ink, plate, etc.) and printability (ink volume, pressure, ink balance, etc.) Process data to determine the following copy elements of the system.
- Black and white field adjustment range;
- Grey balance curve;
- Fixed level curves and black version curves for different manuscript types;
- The color saturation of different original types;
- The maximum total ink volume for different paper types;
- The dot gain rate of printing or proofing;
- The principle of clarity;
- Specification for printing and proofing.
1. Black and white field tone range: This is an important indicator of image quality. The larger the range of gradation, the greater the image contrast, the larger the gamut of copying, the better the visual effect, and the stronger the three-dimensional effect. However, the range of adjustment is limited by the conditions of the post-process. If the white field dot on the color separation film is too small, it may not be printed on the printing plate. If the dot size is too large, it may become a stencil after printing/proofing. Different printing and proofing procedures have different gradation ranges (ie, the same minimum dot area and maximum dot area). This needs to be determined after careful testing according to actual conditions.
For different manuscripts, the range of tonal adjustments is also slightly different. For example, if you use the landscape tone range of landscape manuscripts as the standard (for example, 2% to 88% for yellow and magenta, and 4% to 94 for cyan) %, black version is 0 ~ 75%), the oil painting manuscript and the color version of the tone range should be wider (such as the width of 2% to 3%); character manuscript tone range to be slightly narrower (such as narrow 3% ~ 5 %); while the Chinese version of the color version of the tone range should be narrower (such as narrow 5% to 7%), but the black version to lengthen 10% to 15%.
2. Gray Balance Curve: In the process of determining the range of tone, at the same time, determine the dot percentage curve of each color separation (yellow, magenta, and cyan) that can guarantee the restoration of the original neutral ash. For example, white field (2% for yellow, magenta, 4% for green), middle tone (39% for yellow, magenta, and 50% for blue), dark field (yellow, magenta, 88%, green 94%). For different post-process conditions, especially the ink hue, the gray balance curve is very different. Whenever major post-process conditions are changed, a new gray balance curve must be confirmed.
3. Fixed level curves and black version curves for different original types: Since the original has transmission and reflection points, the density range of different originals is not the same, and some abnormal originals may be too thin or too thick, so for transmitted originals and reflections The manuscript can be set with 5 fixed-level curves, respectively, corresponding to different levels of curves through different gamma values, to adapt to different density ranges and different thickness of the original. Using the middle tone as the standard value as a fixed-level curve, the other four levels of the curve correspond to the midtones to light up -5%, -10%, and the midtones to increase the weight of +5%, +10% (percentage of the outlets).
Different manuscripts have different black curves. For example, the length of the black version of the landscape manuscript is the standard (for example, 0 to 75%). The black version of the Chinese painting needs to be lengthened (10% to 15%); the black version of the character manuscript It should be shorter (5% to 7% shorter); the black version of watercolors and gouache should be shorter.
4. Different original types correspond to different color saturation settings: In principle, originals with a relatively flat and thin color must be processed with increased color saturation, while thick originals should be reduced in color saturation. Based on the final proofs, set the standard color saturation. For the overall color cast, local color cast can be handled by different color correction methods (Image/Adjust).
5. The maximum total ink amount required for different papers: The total ink volume of imported coated paper is allowed to reach 340%-350%; the total ink volume of domestic coated paper is 320%-330%, and the total ink volume of offset paper is 280%-300 %, and so on.
6. Dot gain ratio (compensation amount) setting for different types of originals: In general computer software, the built-in compensation amount for the dot gain rate is 20% (this is not the actual enlargement rate of the midtone dot, but the relative enlargement rate). According to the practice, the dot enlargement rate mainly depends on the ink characteristics and printability. If the dot gain compensation rate is not corrected for the built-in value, the effect of the image duplication tends to be the result of the middle tone emphasis and dark tone levels. In general, the original dot gain compensation value should be 28% to 32%, and the transmission original should be 24% to 28%.
7. The principle of sharpness emphasizes: In the process of image duplication, the clarity of the final copy is closely related to the clarity of the original document, the magnification ratio, the number of screens to be connected, and whether the sharpness processing is appropriate. Insufficient sharpness processing or improper image processing will result in poorer definition. If sharpness is handled excessively (such as sharpening, false light masking, and excessive edge sharpening), noise and relief will appear. Usually when the computer processes images, whether it is shrinking/enlarging, color space conversion, input/output precision conversion, image compression/decompression, and moiré/smoothing/noise processing, it will directly affect the clarity of the output image. . Therefore, for different manuscripts, different magnifications, sharpening radius, sharpening intensity, and threshold setting must be continuously summed up through practice, and the image should be repeatedly and repeatedly processed as much as possible.
8. Standardization of printing and proofing process 2. Calculation of system management of the executive version The so-called “system management†refers to ensuring the consistency of manuscripts, computer screens, proofing and proofing. In addition to the printing and proofing procedures, the system management includes the following:
1. Input scanner calibration: The purpose of the calibration is to make the image data input by the scanner into the computer, which should basically represent the characteristics of the color document, ie whether it is a translucent document or a reflection document, its reference white field after scanning, neutral gray balance, The basic characteristics such as the level curve, the basic color, and the reverse color can be normally reflected in the image data. Therefore, it is necessary to continuously correct the relevant parameters in the scanning software, so that the output proofing is basically consistent with the original document without using computer image processing software. If the scanner can't be calibrated often, relying on computer software to correct the image data not only takes more hours to deal with the image injury, but also the image effect is difficult to maintain the same.
2. Calibration of the computer screen display: If you can achieve the screen display and the effect of proofing / printing, it can achieve the "What You See Is What You Get" realm. However, due to the fact that there is a large gap between the color gamut displayed by the fluorescent screen and the color gamut of the printed ink, it is impossible to achieve the complete agreement between the two. However, if the screen display is not calibrated, and the operator lacks experience in determining the color separation data, then the effects of the computer processing and the expected effects will be completely different, and the processing results of different workstations will be very different. Regarding the screen calibration method, we described it in "Application of Standard Color Image Data (SCID)" (see "Printing Standardization", 1997, No. 4), that is, using a standard image data independent of the input scan to output component color chips, Under the premise of stable printing and proofing process conditions, proofs are obtained, and then screen calibration software (such as KNOLL software) is used to compare the proofs, and after the color balance, brightness, and Gamma curve are adjusted, the screen display is basically close to proofs.
Here is what we need to explain. Many computer operators often use commercially-available chromatography as a reference to determine color reproduction, but the effect is poor. This is because the various raw materials and processing conditions of this chromatogram are different from those of its own after-processing. The effect of color reproduction cannot be the same. The best way to do this is to use the chromatograms that you need to proof or print after you stabilize the conditions of the post process.
3. Calibration of color printer or digital proofing system: In general, ordinary color printers can rarely be calibrated, often through computer output driver software. If a corresponding printer can be selected for a long time, the output effect is better, otherwise the output effect varies greatly. The digital proofing system itself has calibration software, as long as the digital standard output (system comes with it) or standard image chromatogram (such as SCID standard color image data) is compared with the traditional proofing effect, after adjustment by the calibration software, basic Digital proofing can be consistent with traditional proofing. Regardless of whether the dot structure of the digital proofing system is a conventional amplitude modulation network point or a frequency modulation network point or a continuous tone structure, various indicators such as sexual gray balance, color reproduction, and hierarchical reproduction can be compared with conventional proofing.
4. Calibration of the output image-setter: adjustment of the linearization of the film is performed under the condition that the film and the developing conditions (development time, developing temperature, developer replenishment amount, etc.) are fixed, and the alignment needs to be calibrated. The adjustment of the laser intensity is to ensure that the density on the dichroic plate can reach or exceed the density of the substrate at least 3.5D (or the core density of the dots is 2.5D or more). The software linearization adjustment is to ensure that the actual dot percentage value on the color separation sheet is consistent with the percentage value (tone value) of the CMYK dot displayed on the computer, and the error should be less than ±2%. Check the gradation value of the test ladder on the color separation film every day. If the above error is exceeded, adjust the film linearization.
Third, the operation of computer-based plate management "Operation management" refers to the daily production of job flow management. There are the following basic requirements:
1. "Qi, Qing, Ding" of user's work: That is, the user's manuscript, manuscript, layout should be neat, the user's process requirements should be clear and clear, the user should determine (recognize) the final proof.
The most important thing for Qi is the layout requirements. Normally, there is a difference between formal computer design and creative design. Design workstations often take up a long time and require repeated discussions with users. Under normal circumstances, the design workstations are not networked with the system. You can use disk to exchange files. The average user does not attach much importance to the layout, nor is it standardized. The process requirements are not specific and unclear. The layout changes at random will often cause plate rework, invalid machine times, and significantly reduced efficiency.
Layout design itself is a technical work that embodies the user's design style and level. It often goes through layout design by a professional design company in foreign countries. The original and layout design disks are provided to the platemaking company. At present, China still cannot reach this level, and it needs to gradually train users to improve the user's design level and standard level. For users who are not capable of designing their own layouts, the plate-making company can design layouts for users, but the user’s Layout requirements must be clear and specific.
The user's process requirements include both the layout's own requirements and the technical requirements for images, text, and background. For example, the opener of the page
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