Digital proofing (a)

There are currently at least two situations where digital proofing technology must be used: First, the final result of the prepress operation is directly recorded on the plate. This is known as computer-to-plate (CTP); the second situation is that the prepress preparation result is directly Digital printing system output. In both cases, the step of outputting the post-printing film is skipped. There is no reason to use the profiling process for analog offset printing.
First, digital proofing and digital printing from the computer to the proofs and digital printing with the principle of difference, the only difference is the output speed and output purposes. The digital graphic output aimed at proofing uses a technology similar to digital printing. Its focus is on checking how the results of the digital workflow will be displayed during actual printing, and as a technical basis for large-volume printing. Due to this feature, the speed requirement for digital proofing equipment is not the main factor. The key is the gap between the results of digital proofing and the actual printed matter. Through years of hard work, with the participation of color management systems, digital proofing results have become more and more close to traditional offset printing, and have been accepted by more and more printers.
Digital Proofing is a key technology that supports CTP workflow-based printing of an overall digital workflow. It not only involves customers but also affects the printing shop. Both the customer and the press operator are required to receive the most basic training in various digital proofing technologies. They should be made aware of the copying technology characteristics adopted by different digital proofing technologies, as well as the screening technology determined by the copying characteristics and corresponding to the color reproduction requirements. The number and limits of the number of screens can be achieved. The press operator must abandon the analog half-tone proofing process, telling them that even if the traditional printing process is to achieve the same effect as the digital proofing, it is not difficult.
Second, the characteristics of the CTP workflow The CTP workflow omits the output to the film, the process of recording the color image of the machine to expand the phenomenon of dot expansion will cease to exist. Therefore, an important feature of the CTP workflow is that the dot enlargement is much smaller than the use of film to record and reprint. Therefore, the output curve (transfer function) when the page is recorded on the imagesetter cannot be used; the press operator must also understand the CTP seal. The difference between the version and the PS version requires different ink balance adjustment parameters. When the metal CTP plate is intended to be used in the workflow, the printing conditions will also change due to the decrease in the dot gain value, which will affect the ink density setting and the leveling curve of the image. In contrast to traditional workflows, staplers need guidance so that the large format digitally discharged can meet all printing and binding requirements.
The key issue in implementing the CTP process is to solve digital proofing. Digital proofing is imperative once the film has been removed from the workflow. In theory, digital proofing results should reflect the same halftone dot shape, number of screen lines, and gradation variations as the printing process. However, most digital proofing methods generally cannot simulate the halftone dot properties in actual printing, because some digital proofing devices do not use halftone screening technology to simulate continuous tone originals (such as continuous tone digital proofing devices), even if The digital proofing system based on halftone technology may not necessarily produce the same dot structure as the CTP plate. The proofing and plate generation in the CTP process are two independent processes. Therefore, the dots on the sample draft and the dots on the printed matter are played. It is often different. Therefore, the user must notice that the digital proofing and recording to the plate are two RIP processes, which is the main reason why the proofs and plates have different levels of change and resolution. In fact, the printing company should understand that even if the analog proofing or offset proofing process is used, whether the proofing result reflects the actual production effect of the printing process is also uncertain. (To be continued)