Today's publishing and printing field is based on modern computer and network technology, and is marked by digitalization. Production technology and processes have begun to comprehensively change from traditional analog or analog-digital mixed processes to a new digital production process, and gradually move toward high quality and high quality. The development of efficiency, high dynamic, real-time and personalized production process. Therefore, how to meet the requirements of various printing methods, printing conditions, and color samples of printed products in the shortest time and the most optimized method has become the bottleneck and research hotspot in the quality control of publishing and printing production processes.
1. Proofing and its function Proofing is the key link between pre-press and printing in the printing production process. It is an important method 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 not only be used as a post-press process to check the effect of pre-press platemaking, but also as a pre-print process to simulate printing for trial production, to find the best matching conditions for printing and provide ink color standards. Therefore, proofing can not only check the errors that may occur in the process of design, production, production, printing, etc., but also provide production basis for printing and become the user's acceptance standard.
In the actual printing production, it is of great significance to reach the acceptance standard of the final effect of the printed product with the customer before printing, to avoid content printing errors, reduce printing risks and costs, and ensure printing quality. So the role of proofing is:
(1) Provide customers with standard approval proofs: proofs are the finished products of a professional plate-making company, and the client's signing only marks the completion of the entire plate-making process.
(2) Provide basic control data and standard color proofs for printing: "Only customers can print on the machine after signing samples" is the principle of the printing industry to ensure the accuracy of the printing content and quality, and to distinguish between the responsibilities of the two parties. The basis for adjusting the printing environment.
(3) Error check: Through the proofs, you can fully check the quality of each process from the original to the film before printing, and find errors that exist or may occur in the printing, so as to correct the errors and reduce the risk of production. Therefore, proofing has the functions of finding errors in pre-press operations for users and printing units, providing various types of proofs for printing, and as a basis for reaching contracts with customers before printing. In short, the key to proofing is to simulate the printing effect, find errors in pre-press work, and provide relevant standards for printing.
2. Digital proofing and its characteristics
On DRUPA2000, many publishing and printing solutions based on computer and network technology were launched, marking that the traditional publishing and printing industry has begun to fully enter the era of digital production. Digital proofing refers to a new type of proofing technology based on digital publishing and printing system, which processes page graphic information in the process of publishing and printing according to publishing and printing production standards and specifications, and directly outputs color samples. The current general process of digital proofing is shown in the figure below:
(Digital proofing flow chart)
From the above flow chart, we can see that digital proofing is a key process link in the digitization of publishing and printing process, which directly restricts the production process and product quality of publishing and printing.
1. The principle of digital proofing The working principle of digital proofing is different from that of traditional proofing and printing. Digital proofing is based on the digital publishing printing system (CIP3 / CIP4), using the same page of graphic information (RIP data) to reproduce color graphic information by the computer and related equipment and software, and control the quality of the printing production process. At present, the digital proofing system is composed of digital proofing output equipment and digital proofing control software. Digital proofing output device refers to any color printer that can output digitally, such as color inkjet printer, color laser printer, color sublimation printer, color thermal wax printer, etc., but currently can meet the printing speed and format requirements of publishing and printing , Screening methods and product quality are mostly large-format color inkjet printers, such as HP5000 / 120, EPSON7600 / 9600, ROLAND, ENCAD, NOVAJET, etc.
The digital proofing software includes RIP, color management software, layout, control data management, and input and output interfaces. It mainly completes the digital screen of graphics, page assembly and splitting, ink color gamut and printing ink color gamut. Matching, data storage for different printing methods and processes, and data exchange between various devices 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 and the price is low, so the knowledge and experience requirements of the proofing staff are lower than the traditional proofing process, which is easy to popularize and promote.
2. The process and characteristics of digital proofing The process of digital proofing is: making page electronic file-RIP-digital proofing. The operation procedure is: the system sets the acceptance of the electronic file-selects the proofing material for the layout-digital proofing. A set of digital proofing four-color version only need 15-30 minutes, a set of digital proofing software can control multiple digital proofing machines with high productivity. The characteristics of digital proofing are not only different from the traditional proofing machine flat round printing method, but also different from the round round printing method of the printing machine, but based on the color range of the printed product color and the same RIP data as the printed content, Use digital proofing large color gamut space to match printing small color gamut space to reproduce printing colors, without any conversion can meet the requirements of various printing methods such as flat, convex, concave, soft, net, etc., can be printed according to the actual user The production of proofs based on the situation 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 controlling the restoration of up to 928 color areas, which is far superior to the traditional proofing Controlled field density, 1%, 2%, 15%, 50%, 75%, 98%, 99% outlet restoration, etc. It also greatly facilitates operators who are used to judging or controlling the quality of proofing or printing quality by using a magnifying glass to look at the shape of the dots in the domestic pre-press and printing of color offset printing, which reduces the requirements for personnel quality and experience and improves control The accuracy of the data.
4. Comparison of digital proofing with traditional proofing Digital proofing, because it integrates the latest theory and technology in the field of publishing and printing, compared with traditional proofing 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 and have good openness;
(6) In line with the technical advantages of CIP3 / CIP4 development direction.
In short, digital proofing technology is an emerging technology and a key link in the modern printing 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 is foreseeable that digital proofing will eliminate traditional proofing within a certain period, create new value and benefits for users, and lead users to move from the analog era to the digital era.
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