Digital Plate System Quality Management

First, scan the input part - re-digitization of foreign film

Since the entire process of computer-to-platemaking is entirely digital, foreign dichroic films must also be able to be re-scanned into numbers for imposition, which is commonly known as dot-dot scanning (copy-dot). Its main features are:

Network copy: The original film will be re-copied to become an electronic file that can be used for imposition;

Digital Networking: Combining four-color film and network processing to restore it to a color image while retaining the details of the image. The modified file can be edited using various software.

Second, comprehensive color management

Since computer-to-plate must use digital color proofing, how to simulate actual printing results with digital color proofing is critical. In addition, the screen display also needs to be matched with printing, so the color management of the entire system must be taken into consideration.

The International Committee on Illumination's standard color space, CIELab, is device-independent and covers the entire visible color gamut. At the same time, according to the standards of the International Color Consortium, a relevant profile file profile is defined for each device to describe the color characteristics of the device.

The basis of color management is to ensure that all devices are in the color reproduction system. To achieve the goal of color management, device calibration, characterization calibration, and color gamut conversion are indispensable in this process.

Equipment calibration: Some people think that the term "equipment calibration" refers to all the steps to get accurate color, perhaps meaning that the copied color is calibrated to match the original color. But in reality, calibration equipment is just one of three steps in color management. The device calibration itself does not guarantee the matching of the color. It only calibrates the performance of the device itself and only guarantees that the device (such as: scanner, monitor, printer) meets the required specifications of the standard, and provides a way to ensure that it is in a period of time. Stable work in time.

Profiling: A method of measuring and quantifying the color space, color gamut, and color characteristics of a particular device when it is known. It is used to determine how to capture color or record color when an input device or an output device is calibrated. Characterization calibration is the process of actually generating a device description file for a scanner, monitor, printer, and so on. The characterization calibration data is used by the color management software, so the characterization calibration is a process in which the device cooperates with the color management software to describe the color gamut of the device. To achieve characterization calibration, the device itself must be equipped with a high-performance color sensor, with color management software to achieve true characterization calibration; otherwise, these devices must use a separate calibration device and color management software, In order to achieve characterization calibration.

Color gamut conversion (color transfer): This is the process of converting image colors from one device's gamut data to another device's gamut data. Through color management software, color gamut conversion can be achieved manually or automatically. Switching between the gamuts of different devices is often referred to as gamut mapping.

Third, the electronic layout

Modern printing has become more and more demanding on the time of plate making. Weekly news weekly, in order to ensure the timeliness of news, from the deadline of the manuscript to the listing of the magazine, its effective working hours are calculated in hours. In traditional platemaking methods, it is all done by hand imposition by the imposition workers in the plate room. Its quality, speed, etc. are greatly limited. With the advent of CTP technology, the combination of electronic imposition technology and large-scale prepress productivity has become increasingly important.

Electronic imposition is an imposition process in which the pages are discharged in the order of the pages of the printed pages for the printing of books, magazines, albums, and number books. The wide application of electronic layout technology, its role in ensuring the quality of printed products is very obvious. At present, magazines on the market often suffer from inaccurate rules for individual color pages, which seriously affect the printing effect. Time is not tight, you can rework, and when the time is tight, only go with it. From a technical point of view, the current phenomenon will be solved with the application of electronic layout technology. Compared with the traditional method, electronic layout has the following advantages:

(1) Manual imposition Using scissors and tape, time and precision are difficult to guarantee. The computer make-up is to make imposition and then separate color, saving time and effort, and high efficiency.

(2) General computer imposition personnel can easily make up one version with more than one minute, which is approximately ten times more than traditional manual efficiency.

(3) Manual imposition After many copies, the quality is attenuated, the computer imposition is an image, the quality of the dots is high, and the material consumption is low.

Fourth, digital color proofing

From the production point of view, the color printing quality is a process based on the principle of dot color rendering, and the production requires strict precision and stable repeatability. However, there are many factors that affect the printing color, such as the characteristics of the paper, ink ink layer thickness, printing pressure, air humidity, and even the quality of the plate. Some factors will influence each other, and the increase or decrease of each factor will cause other factors to change, which will affect the quality of printed color. Therefore, it is necessary to estimate the combined effects of various factors on the print before production to make adjustments, and proofing is a production simulation before actual printing.

In general, proofing provides the following three functions: First, it is used to check the effect of color separation and plate-making to determine whether the color of a picture is processed correctly and provide a basis for revision. Second, it is used to check the technical requirements of film registration and dot gain, as a reference for actual printing. Third, as a communication tool, the customer will sign and confirm before printing, and it will be used as a standard for receiving goods in the future.

The computer-to-plate system must use digital color proofing. Traditional proofing generally uses a monochrome flatbed printer. Ink supply and ink transfer are determined by the master according to the situation. The goal is to make the proofing effect pleasing to the eye. However, this approach often sacrifices the stability of the proofing color, and less takes into account the printing requirements. With the development of computer-to-plate technology in recent years, CTP requires a set of reliable digital processes to properly handle the production process from platemaking to printing. Image data technology has become more mature, and proofing has begun to develop in the digital direction. One of the most important contributions of digital proofing is to improve communication with customers. In the absence of digital proofing before all, it is necessary to first out of the film, and then there is proofing, in case of customers are not satisfied with the color, we must re-filming and then proofing, often a waste of money time. With digital proofing, customers can first see the proofs and wait for their satisfaction to export the film. This will not only save costs, but also increase communication, and it can even be proofed on the parting side, which is an important breakthrough in the printing process.

Fifth, server and raster image processor

The computer-to-plate system must have a powerful server and raster image processor to enable centralized storage and archiving of large-capacity files and print queue management.

The CTP system does not use film, so digital proofing must be used. When digital proofing, such as the final product output, uses its own RIP, there is often a case where the proofs are inconsistent with the final product. Therefore, it is required that both use the same RIP. The RIP at this time should have the function of “RIP once, output multiple times”, that is, the same data after RIP processing can be used for digital proofing and final product output at the same time, and requires RIP to output different resolution data according to different devices. . Using the same RIP data, you can make proofs accurately reflect the final product situation, to avoid or reduce the color cast and the opportunity to make mistakes.

Sixth, the quality of employees

With the continuous penetration of high-tech represented by computer technology and network technology into the printing industry, the quality of personnel in the domestic printing industry has greatly increased in recent years. The industry already has a group of highly qualified personnel, which is also the CTP technology in China. The application laid a certain foundation.

With the continuous development of China's economy, high-end printing is gaining more and more markets. This trend is particularly evident in the more developed regions of eastern China. With the CTP system, the prepress process has been fully digitalized, so the quality of the plate printing is better. After China's accession to the WTO, the printing industry as a whole will gradually establish standards and procedures that are in line with international standards. The impact of the policy on the domestic printing industry is enormous. The development of CTP in the country will benefit from the country’s gradual release of the printing industry.