How does color management ensure the accuracy and stability of the output color?
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The color management system running in the color desktop system requires the stability of output, printing, proofing and printing quality to ensure the accuracy of the output color. On the one hand, color management controls and standardizes the output device, and establishes a feature file, that is, a target feature file, to be integrated into the color management system.
1. Correction and description of proofer and printer
Color proofs, whether analog or digital, or pre-press proofs or proofs, are key tools for monitoring each part of the image reproduction process. To ensure accurate color proof, the important role is: 1 for traditional analog proofing, To the accuracy and stability of the output four-color ink sample color, there are three indicators that must be controlled and standardized.
A. Equipment Standard: The equipment is calibrated to ensure that the proofer is in optimal working condition, including proper pressure, standard plate temperature and optimum performance of the air blanket blanket.
B. Material standards: First, standardize the same brand, the same series of inks, do not smash and use each other. Now there are many units of four-color inks that are mismatched, resulting in a different profile from the scanner, which directly affects the accuracy of the calibration, and the correct image file cannot be obtained by scanning. The second is to standardize the paper. In principle, the same type of paper should be used for proofing and printing. If the proofing and printing use only one kind of ink and use three types of paper, such as coated paper, matte paper and book paper, three kinds of papers should be established. Line documents to the press.
C. Quality standards: First, the standard density value of four-color inks is standardized, which is the core of color management for proofing and pre-press operations, because the variation of the density value of the field has a great influence on the color of the whole sample. The second is to standardize the relative contrast (K value), which is an important indicator to measure whether the density of the proof (printing) is sufficient, and whether the dot gain is in compliance with the standard range. Generally, the quality of the proof is appropriate, and the K value is above 0.40. Excellent.
At present, some proofing companies generally have two problems. One is that the one-sided pursuit of the dot gain is smaller and the better, and the small dot in the center of the dot is caused, so that printing cannot be caught up. This is a misunderstanding. The proofing dot increase should have a standard range, and it is not necessary to ignore the printing and the one-sided pursuit of dot gain is smaller. Practice has proved that 50% of the dots increase C, M ink is 8%-10%, Y, K is 12%-13% is appropriate. Second, the proofing uses DIC Japan soft special ink, which has a large gap with the printing ink, which often causes a large difference in color between the printed matter and the proof, which makes the customer unsatisfied with the printed product. Therefore, it is important to establish the profile file of this ink by using the same brand of ink for proofing and printing. Prepress work must create conditions for the final printing of good products.
2 In terms of digital proofing, the first thing to do is to simulate the color proof effect of the traditional proofing machine proof (printing), and then create the printer's characteristic file by:
A. Through the calibration of the printer, the printer is in an optimal working condition, including determining the type of printing paper used.
B. First, use the traditional analog proofing to produce a standard proof of ISO/IT8.7.3 color standard for automatic color correction by the digital proofing machine. The IT8.7.3 color code contains 928 color blocks, and has the largest overlap area for detecting the ink overprinting effect. There are Y, M, C, and K scales for detecting the density of the ground, and there is an overprint for detecting the gray balance CMY. District, etc., the content is complete. Of course, all kinds of soft can also use different formats, different color blocks of color code files according to their needs, such as Creo. The game angel color management software spw uses the kmart color scale, which contains 450 color blocks. The color code file is generally a TIFF or PS file.
C. The chromaticity values of 928 color patches on the IT 8.7.3 color scale were measured with a colorimeter or spectrophotometer.
D. The measured data is input into the printer profile generation software, and the profile generation software compares and analyzes the chromaticity data of the primary color code and the output color block to generate a new characteristic file of the printer.
With the ORIS Color Tuner version 3.1 color management and digital proofing system, the color of the sample output directly on the Epson 5000 printer is basically the same as the color of the traditional analog proofing. 95% can be achieved by automatically correcting offset proofs, and gravure proofs can achieve 90% accuracy. The system also provides users with a color adjustment tool Fine Tuning with a good operation interface, which can handle both spot colors and background colors, as well as flexible level adjustment and selection tools, which can be used for different tone levels and A variety of colors help to accurately process, to achieve the analog proof (printing) ink color effect. Practice has proved that digital proofing technology has developed to the present day, it should be said that it is mature, which is the best choice for color management needs to output accurate color.
In summary, only the output proofing standardization, the establishment of multiple ICC profiles in the proofing environment, to ensure the accuracy and stability of the output color, on the one hand to the input scanner, so that the application of this profile file to complete the scanning color separation; The aspect is provided for printing standard proofs, so that the input scanning and output proofing and printing can obtain the effect of color similar.
2. Standardization
To ensure that the quality of the printing plate is stable and to ensure the correct transfer of the tone of the original image, there are three indicators that must be controlled and standardized.
1 equipment standard
Ensure that the printing machine and PS version of the developing machine are in the best working condition, including the stable light source of the printing machine and uniform illumination, and the automatic refilling device of the developing machine is sensitive.
2 material standards
A. Standardize the PS version of the brand, do not want to use several brands and recycled versions.
B. The developer is compatible with the PS version, so that the concentration of the developer is strictly controlled, the ratio is accurate, and the new solution can be refilled regularly.
3 quality standards.
A. Determine the optimal exposure time, use the UGRA control strip to control the exposure, reach the ladder 4 ladder (0.6D), the resolution is 6μ, the 8μ yin and yang lines are complete, and the step control section is 2% small. Qi.
B. Determine the optimal development speed, the correct exposure should be properly developed to match, the UGRA control strip is used to control the development speed, the hollow point after development is relatively clear, and the corresponding small dot is relatively firm, which proves that the developer concentration is appropriate.
C. It is necessary to replace the PS version of a brand and do a standardized test to ensure that the part of the printed version has good oleophilic water repellency and good blank oil and oil repellency.
3. Phototyper standardization
The laser imagesetter should process the image files processed by the computer and output the CMYK four-color color separation film after RIP. It must ensure that the dot size value of the scanning color separation setting can be accurately transferred to the color separation film. It has three indicators. Control and standardize.
1 equipment standard
Ensure that the photo-aligning machine and the developing machine are in the best working condition, including the stability of the laser light source, select the dot shape, mesh angle, mesh line number, and the automatic replenishing device of the developing machine.
2 material standards
A. Standardize the film brand, select the film according to the characteristics of the laser light source of the photo-aligning machine. For example, Agfa Photographic Machine is best to use Agfa film, Dolev800 photo-setting machine selects Kodak 2000, and its dot reproducibility is good.
B. To achieve stable development conditions, the selection of the pharmacy compatible with the film brand, most of the current use of Ai Xixi 1000 sets of drugs, good quality, no crystallization.
3 quality standards
To achieve accurate linearization, one is to control the correct exposure, so that the solid density of the color separation sheet reaches 3.8-4.5, the best is 4.0-4.2, and accurate dot transmission, such as linear scale The film reaches 2%, 50%, 98% of the dot reduction, 50% dot ± 1%, if it does not meet the standard, adjust the laser light amount. The second is to stabilize the development conditions, strictly control the concentration, temperature and replenishment of the developer, to ensure that the bottom ash density is controlled below 0.05, so that the white base is more transparent.
In summary, the stability of the post-process and the standard quality standards are the basis for the stability and improvement of the entire system. It will give the scanner a correct feedback and set the network points within a reasonable range. The transmission between the devices ensures that the color of the image after scanning the color separation can be approximated by the color of the preview and the output proof.