The digital proofing technology is completely controlled by digitalization, which has changed the previous complex printing production process, reduced the cost, and greatly improved the stability of the platemaking and printing quality. In gravure printing, a process that does not require the use of film, digital proofing is a more suitable proofing method, as shown in Figure 2.
Figure 2 Gravure digital proofing
Digital proofing technology is already very mature and fully meets the needs of gravure platemaking. The design elements in the gravure plate are mostly graphics, images, and spot colors, which are mainly due to the fact that the colors represented by the spot colors are more uniform, brighter, and more stable than the multicolor overprints. The use of spot colors in the inverted white graphics or text section can reduce registration difficulty. Therefore, to evaluate the pros and cons of gravure digital proofing, it is the key to verify the accuracy of the proofing system's restoration of spot colors. At present, digital proofing technology not only satisfies the general four-color proofing, but also improves the ability to support spot colors. For example, a professional digital proofing system can be used to control the overprinting and trapping of spot colors and the control of spot color transparency. Problems often encountered in gravure printing processes such as spot color transitions provide good solutions.
The advantages of digital proofing mainly include the following points.
(1) There is no need to output film or make plate cylinders, which can reduce costs while shortening the production cycle.
(2) Proofs produced based on inkjet technology are generally more stable in quality.
(3) Digital proofing is an important part of digital printing. Its unique stability can provide standards for the entire printing process, providing a powerful guarantee for the improvement of printing quality.
The disadvantages of digital proofing mainly include the following points.
(1) Some digital proofing systems do not ensure the integrity of the document data.
(2) A digital proofing system with a processing mesh adjustment function requires a relatively high cost.
(3) Spot colors and metallic colors cannot be accurately reproduced and a specific system must be used.
Undoubtedly, with the continuous development and improvement of color management technology, digital proofing will show greater advantages in the printing process, and occupy a dominant position.
Gravure digital proofing system
The digital proofing system is based on the actual printing characteristics of various regions or companies. It controls the printer's ink jet volume to realize the printer's color gamut simulation.
Whether the color provided by digital proofing can exactly match the printing sample at the back end depends on the following points.
(1) The printing process of a printing plant must be standardized and stable. If adjustments and improvements are made to the printing process, the printing characteristics data must be re-acquired.
(2) The printer used in digital proofing should choose a reliable and high-speed inkjet printer, which requires high printing accuracy, accurate jet ink droplets, and a better color gamut than the printed color gamut. Moreover, changes in these factors will affect the results of the proofs, so these factors must remain stable. For example, some users do not know enough about the paper. After replacing the cheaper paper, they find that the printed proofs have color deviations. They think that the digital proofing system is unstable.
(3) Digital proofing software supports ICC-based color management systems, accepts commonly used file formats, and supports spot color processing. Digital proofing software is divided into color digital proofing software and real network digital proofing software. True Dot digital proofing software not only manages colors like color digital proofing software, it can achieve color simulation of back-end printing, but also can accept RIP data to ensure the consistency and integrity of the transmitted data. Therefore, the proof of drafting realized by True Dot digital proofing software has higher security.
The point to remember is that both digital proofing and mock proofing must accurately represent the final print result. In gravure printing, digital proofing is a more appropriate and simpler proofing method. One of the most important things to consider when using digital proofing is the integrity of the data. The other thing is of course the accuracy of the colors.
Digital proofing test sample
The digital proofing test sample provides various data sources that are necessary to debug the digital proofing system, as shown in Figure 3.
Figure 3 Digital proofing test sample
Digital proof test samples must contain material images, color graphic files, and data control information. The material diagram is very intuitive, easy to distinguish color differences, and can be used to visually evaluate image quality. Each color block of the color graphics file has an electronic standard value. The printed color image file is measured with a spectrophotometer, and the measurement data is compared with the standard data to accurately control the output device (such as a printing machine). Color attributes. Data control information is an effective way to regulate the quality of back-end printing by detecting yellow, blue, black, solid density, print contrast, overprint rate, consistency of printing, and leveling of ink.
It can be seen that the digital proofing test sample combines digital control and visual evaluation to ensure the feasibility and comprehensiveness of the test work.
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