Pre-RIP Proofing Trap—Principles and Methods of Digital Proofing

Pre-RIP Proofing Trap—Principles and Methods of Digital Proofing

Today's publishing and printing field is based on modern calculators and network technology, and is marked by digitization. Production technology and technology have begun to comprehensively change from traditional simulation or analog-digital hybrid technology to new digital production technology, and gradually to high-quality, The development of high-efficiency, high-dynamic, real-time and personalized production processes. Therefore, how to meet various printing methods, printing conditions, and printing product requirements for color proofs in the shortest time and in the most optimal way has become the bottleneck and research focus of today's publishing and printing production process quality control.

1. Proofing and its function

Proofing is the key link between prepress and printing in the printing production process. It is an important means of quality control and management in the printing production process. It is extremely important to control printing quality and reduce printing risks and costs. Proofing can not only be used as a pre-press and post-process to test the effect of pre-press plate making, but also can be used as a pre-print process to simulate printing for trial production, seeking the best matching conditions for printing and providing ink color standards. Therefore, proofing can not only check the possible errors in the process of design, production, film production, and printing, but also provide production basis for printing and become the user's acceptance standard.

In the actual printing production, reaching the acceptance standard of the final effect of the printed product with the customer before printing is of great significance to avoid the printing error of the content, reduce the risk and cost of printing, and ensure the printing quality. So the role of proofing is:

(1) Provide customers with standard approval proofs: The proofs are the finished products of a professional plate-making company, and the customer's signature marks the completion of the entire plate-making process.

(2) Provide basic control data and standard color proofs for printing: "Only after the customer signs the sample, it can be printed on the machine" is the principle of the printing industry to ensure the accuracy of the printing content and quality, and to distinguish the responsibilities of both parties. It is also the basis for the printing workers. The proofs need to be adjusted to the printing environment.

(3) Error inspection: Through the proof sheet, the quality of each process link from the original to the film can be comprehensively checked, and the existing or possible errors in printing can be found, so as to correct the errors and reduce the production risk.

Therefore, proofing has the functions of (1) discovering errors in prepress operations for users and printing units; (2) providing various types of proofs for printing; (3) serving as the basis for reaching contracts with customers before printing. In short, the key to proofing is to simulate the printing effect, find errors in the pre-press work, and provide relevant standards for printing.

Second, digital proofing and its characteristics

At DRUPA 2000, a number of publishing and printing production solutions based on calculators and network technologies were launched, marking the beginning of the traditional publishing and printing industry's full entry into the era of digital production. Digital proofing refers to a new proofing technology that is based on the digital publishing and printing system, and processes the page graphic information according to the publishing and printing production standards and specifications in the publishing and printing production process, and directly outputs color samples. At present, the general process of digital proofing processing is shown in the following figure:

As can be seen from the flow chart at the end of the article, digital proofing is a key process link in the digitization of the publishing and printing process, which directly restricts the production process and product quality of the publishing and printing process.

1. The principle of digital proofing

Digital proofing works differently than traditional proofing and printing. Digital proofing is based on the digital publishing and printing system (CIP3/CIP4), using the same page graphic information (RIP data) to reproduce the color graphic information by the calculator and its related equipment and software, and to control the quality of the printing production process. At present, the digital proofing system consists of two parts: digital proofing output device and digital proofing control software. The digital proofing output device refers to any color printer that can output digitally, such as color inkjet printers, color laser printers, color sublimation printers, color thermal wax printers, etc., but the printing speed and format that can meet the requirements of publishing and printing at present , Screening methods and product quality are mostly large-format color inkjet printers, such as HP5000/120, EPSON7600/9600, ROLAND, ENCAD, NOVAJET, etc. Digital proofing software includes RIP, color management software, imposition, control data management and input and output interfaces, etc., mainly to complete the digital screening of graphics and text, page stitching and splitting, ink color gamut and printing ink color gamut. Matching, data storage of different printing methods and processes, data exchange between various devices, etc. Digital proofing software is the core and key of the system, which directly determines the process of digital proofing replacing traditional proofing. Because digital proofing adopts digital control, the equipment is small in size and low in price, the requirements for the knowledge and experience of proofing personnel are lower than that of traditional proofing technology, and it is easy to popularize and popularize.

2. Process and characteristics of digital proofing

The process of digital proofing is: making a page electronic file - RIP - digital proofing. The operating procedures are: the system sets the acceptance of electronic files - the selection of proofing materials for the large version - digital proofing. It only takes 15-30 minutes for digital proofing to make a set of folio four-color version. A set of digital proofing software can control multiple digital proofing machines and the productivity is very high. The characteristic of digital proofing is that it is not only different from the printing method of the traditional proofing machine, but also different from the printing method of the printing machine. The printing color is reproduced by matching the large color gamut space of digital proofing to the small color gamut space of printing, and can meet the requirements of various printing methods such as flat, convex, concave, soft, and net without any conversion, and can be printed according to the actual printing of users. It completely solves the problem that it cannot be combined with the subsequent actual printing process, which brings difficulties to printing.

3. Quality control of digital proofing

The quality control of digital proofing adopts the data measurement method of control standard plate (such as IT8) and densitometer (spectrophotometer), focusing on the restoration of up to 928 color areas, which is far superior to the solid density, 1% of the traditional proofing key control. , 2%, 15%, 50%, 75%, 98%, 99% dot restoration, etc. It also greatly facilitates the operation workers who are accustomed to using a magnifying glass to judge or control the quality of proofing or printed matter in prepress and printing of color offset printing, especially in color offset printing. data accuracy.

4. Comparison of digital proofing and traditional proofing

Because digital proofing integrates the latest theories and technologies in the field of publishing and printing, compared with traditional proofing, it has: (1) advanced technology and strong adaptability; (2) fast speed and low cost; (3) stable quality and good repeatability (4) Convenient operation and high reliability; (5) Adapt to the development of new technologies, good openness; (6) Conform to the development direction of CIP3/CIP4 and other technical advantages.

In a word, digital proofing technology is an emerging technology and a key link in the digital production process of modern printing. Digital proofing technology will be continuously understood and accepted by users, and will be continuously improved in the use of the majority of users. It can be foreseen that digital proofing will eliminate traditional proofing in a certain period of time, create new value and benefits for users, and lead users to move from the simulation era to the digital era.