Introduction to Prepress Knowledge of Flexo Printing Process (II)

Understanding (electronic) pre-press for flexo -An introduction for the pre-press novice (Part 6) 8. Device-independent color measurement system if color image data is stored in true color, but not in percentages (CMYK system) Used in). For this situation in the printing industry, there are two more suitable color measurement systems: CIE Lab and CIELuv. In theory, CIELuv is better than CIELab, but due to historical reasons, CIELab system has been widely adopted by the industry. CIELab and CIELuv are regarded as device-independent color measurement systems with very high precision. Moreover, the color space covered by these systems is much larger than any printed color space. Therefore, it can be fully converted into the desired target color space. By storing the image data as CIELab or CIELuv space colors, the image can maintain neutral gray balance and idealization. When the color data is output on the output device, regardless of whether the three primary colors or the spot colors are used, the conversion to the printing color space can be accomplished with the help of a good color management system, and the accuracy is also very high. IX. Color Management and Halftone Digital Proofing At present, most of the publications and articles related to color management have lacked in-depth research on the special requirements of packaging and printing. Since a variety of spot colors are commonly used in packaging printing, a series of special requirements are generated, which greatly complicates the color management work. The following table lists these conditions and their corresponding results. Color Workflow DTP DuPont CromaNet Barco Workstation Quality CCMS Application Quality CCMS Quality CCMSA. CMYK color combination (1) is available or good DTP is very good (2) DC4.1 is very good (2) KB. What is the independent non-primary color (monochrome) isolated part? DTP is excellent (3) DC4.1 is good (3) KC. Transparent non-primary color composition / combination No? Is being tested in DC4.1.5 is excellent (4) K + D. Is the combination of transparent non-primary colors and primary colors? In the test is DC 4.1.5 in the excellent K + The purpose of this table is mainly to describe the four "stages" of color management in packaging and printing. The three workflows listed are just examples. The purpose is to show everyone the fact that not all color management system vendors have taken into account the special needs of packaging printing. In the most commonly used color management systems, the vast majority still remain in the first stage or are in the second stage of the "start line". However, it must be pointed out that the development of the higher stage must take considerable effort. This is only necessary for some manufacturers. As for the halftone digital proof mentioned earlier, the color management is more complicated. Therefore, there is a question: "Do you want to change the direction of investment? Will the halftone digital proofing improve the quality of the proofing?" The answer to this question is quite astonishing - "may not be"! At first glance from the printer's point of view, many customers are asking for halftone proofing. This is understandable, but from a technical point of view, this is actually not of much significance. People may wonder why Looking for reasons from the color management? The main purpose of color proofs is to accurately reproduce the color of the final print! Therefore, if half-tone proofs are used, color management will inevitably affect the dot size daily control and thus match the color of the images printed on the final press. In fact, the larger the deviation of the printed color from the proof color, the greater the control of the color management system must be. It is well-known that the inks used in flexographic printing generally differ greatly in density and color from the three primary colors specified, and that the current half-tone digital proofs match those assigned primary colors. Therefore, the dots we see on this kind of halftone proofs are not necessarily the same as those on the printed ones. For example, for example, cyan printed on a printing press is “lighter” than the half-tone proofer and the tone is “warm”, and the color management system will use a certain percentage of cyan in the proof (for example, 90% ) To replace 100% of cyan, and adjust the other percentages of cyan tones in turn, and add a small amount of magenta to the entire gradation of cyan ink. Therefore, under the effect of the color management system, even a slight change in the cyan ink may cause a large-area gradation change in the printed image. In this case, the reliability of half-tone proofing can be said to be zero. So, why should digital proofs be screened? However, in analog half-tone proofing, the situation is much better. In this kind of proofing system, the only representative is the well-known Cromarin proofing system. The Cromarin proofing system will undoubtedly provide the most reliable proofs for packaging printing. The ideal digital proofs do not necessarily have to be half-tone proofs, but it must be ensured that the colors of the final prints can be reproduced accurately and reliably. In addition, the trapping process and the reproduction of spot colors are also one of the issues that users are most concerned about. In packaging printing, the application of digital proofs is not too common, it depends on the future cooperation between packaging and printing companies and their customers. If we can further shorten the production cycle of packaging printing, and the cooperation with customers is closer than now, reliable (contract) digital proofs will have great development prospects. If the delivery time is very short (or for some other reason), there is no time or it is not possible to generate the same and hand it to the customer for signature, then you must find other methods that can simulate the final print. At present, the latest method must be regarded as sending proofing data. As long as the client has installed a digital proofing system, it can receive proofing data and complete proofing on the client. This method is called “remote proofing”. However, it is required that the client must use a digital proofing system that is as good and reliable as the printing factory and has a stable color to receive data, so as to ensure successful successful remote proofing. If you are unclear about the client's printing system and its data processing functions, will you send the data without hesitation? Can you guarantee the accuracy of the data? If this situation becomes a reality, printing companies will rely on these effective digital proofing systems and may even install the same proofing system at their main customers.