Pre-RIP Trap - Principles and Methods of Digital Proofing

Today's publishing and printing industry is based on modern computer and network technologies, and is marked by digitization. Production technology and technology have begun to fully transform from traditional simulation or modular mixed processes to new digital production processes, and gradually to high quality and high The direction of efficiency, high dynamics, real-time and personalized production processes. Therefore, how to use the shortest time and the most optimized method to satisfy various printing methods, printing conditions, and the requirements of color products for printing products has become a bottleneck and a research hotspot in the quality control of current publishing and printing production processes.

First, proofing and its role

Proofing is the key link between prepress and printing in the printing production process. It is an important means for quality control and management in the printing production process. It is extremely important for controlling printing quality and reducing printing risks and costs. Proofing can be used as a pre-printing process to test the effect of pre-printing, and can be used as a pre-printing process to simulate the printing for trial production, seeking the best matching conditions for printing and providing ink standards. Therefore, proofing can not only detect errors that may occur in the process of designing, making, filming, printing, etc., but also provide production basis for printing and become the user's acceptance criteria.

In the actual printing production, the acceptance criteria of the final effect of the printed product is reached with the customer prior to printing, which avoids the printing error of the content, reduces the risk and cost of the printing, and ensures the printing quality is of great significance. So the role of proofing is:

(1) Provide customers with standard approval samples: Samples are the finished products of a professional plate making company. The customer's sample order marks the completion of the entire plate making process.

(2) Provide basic control data and standard color proofs for printing: “Only customers can sign up before printing on the machine” is the principle that the printing industry ensures the accuracy of the printed content and quality, and distinguishes the two parties' responsibility. It is also based on the principle of the printing worker. The proofs need to be adjusted based on the printing environment.

(3) Wrong inspection: Through the proof sheets, the quality of each process link from the original to the film before printing can be comprehensively checked, and errors that have or may appear in the printing can be found out, so that errors occurring can be corrected and the risk of production can be reduced.

Therefore, proofing has found errors in the prepress operation for users and printers (1); (2) provides various types of proofs for printing; and (3) functions as a basis for contracting with customers before printing. In short, the key to proofing is to simulate the effects of printing, find errors in the prepress work, and provide relevant standards for printing.

Second, digital proofing and its characteristics

In DRUPA 2000, a large number of publishing and printing production solutions based on computer and network technologies were introduced, marking the beginning of a comprehensive entry into the era of digital production in the traditional publishing and printing industry. Digital proofing refers to a new type of proofing technology that directly outputs color proofs based on the digital publishing and printing system, and handles the graphic and textual information in accordance with the publishing and printing production standards and specifications during the publishing and printing production process. The current general process of digital proofing is shown in the following figure:

From the flow chart of the text, we can see that digital proofing is the key technological process for the digitization of the publishing and printing process, which directly restricts the quality of the production process and products of publishing and printing.

1, the principle of digital proofing


Digital proofing works differently than traditional proofing and printing. Digital proofing is based on the digital publishing printing system (CIP3/CIP4), using the same page graphics information (RIP data) to reproduce color graphic information from computers and 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 proof output device refers to any color printer capable of digital output, such as a color inkjet printer, a color laser printer, a color sublimation printer, a color thermal wax printer, etc., but the print speed and format that can meet the publishing and printing requirements are currently available. , screening methods and product quality are mostly large format color inkjet printers, such as HP5000/120, EPSON7600/9600,
ROLAND, ENCAD, NOVAJET and others. Digital proofing software includes RIP, color management software, imposition, control data management, and input and output interfaces. It mainly completes graphic digital screening, page splitting and splitting, ink color gamut, and ink color gamut. Matching, data saving for different printing methods and processes, data exchange between various devices, etc. Digital proofing software is the core and key of the system and directly determines the process of digital proofing replacing traditional proofing. Because digital proofing adopts digital control, the equipment is small in size, and the price is low. Therefore, the requirements for proofing personnel's knowledge and experience are lower than traditional proofing techniques, and it is easy to popularize and popularize.

2, the process and characteristics of digital proofing

Digital proofing process is: production page electronic file - RIP - digital proofing. The operating procedure is: the system sets the acceptance of the electronic file - the large version of the selection of proofing materials - digital proofing. Digital proofing and playing a set of four-color version only takes 15-30 minutes. A digital proofing software can control the productivity of multiple digital proofers. The feature of digital proofing is that it is different from the printing method of the traditional proofer flat pressure circle, and is different from the printing method of the press circle, but based on the color rendering range of the print color and the same RIP data as the print content. Adopt the digital proofing large gamut space to match the printing of the small gamut space to reproduce the printing colors. Without any conversion, it can meet the requirements of various printing methods such as flat, convex, concave, soft, and net, and can be printed according to the user's actual printing. Conditions to produce proofs, completely solved the problem of not being able to combine the subsequent actual printing process to bring difficulties to printing.

3, digital proofing quality control

The quality control of digital proofing adopts the data measurement methods of control reticle (such as IT8) and densitometer (spectrophotometer) to control the restoration of up to 928 color areas, far better than the field density of traditional proofing control, 1% , 2%, 15%, 50%, 75%, 98%, 99% dot reduction. It also greatly facilitates the use of magnifier to monitor the appearance of outlets in prepress and printing in China, especially for color offset printing, to determine or control the quality of the proofing or printing operations workers, reducing the requirements for personnel quality and experience, and improving control. The accuracy of the data.

4. Comparison of Digital Proofing and Traditional Proofing

Digital proofing integrates the latest theories and technologies in 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) adapting to the development of new technologies and good openness; (6) complying with technological advantages such as the development direction of CIP3/CIP4.

In short, digital proofing technology is an emerging technology and a key part of the modern digital production process. Digital proofing technology will be constantly 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 values ​​and benefits for users, and lead users to move from the analog era to the digital era.


Source: Shanghai Printing Forum