CTP Technology and Digital Proofing Technology

Digital proofing, as the name suggests, is based on a digital prepress system. In the prepress design and production process, the page graphic information is handled in accordance with the printing production standards and specifications. The digital output system is used to directly output the color sample, ie, data is used. The original directly outputs the print proofs. Now the most common digital printing technology is to use a large-format color inkjet printer as an output device, which directly outputs and prints color proofs, which are used as the basis for the final printing and printing.

Digital proofing is developed in parallel with color management technology and CTP technology. Compared with traditional proofing methods, digital proofing is fast and cheap. At present, it has become a major means for customers to sign samples. The previous digital proofing was different from the true colors of printed materials because of the different materials and coloring principles used. Ignored.

The progress of color management technology, as well as a large number of experts dedicated to practice and exploration, the current digital proofing technology is quite mature.

Proofing is the most important link in the printing process. At present, even the enterprises in the entire industry adopt traditional proofing as a means of proofreading and sample-taking. For companies with CTP, the application of digital proofing technology is the key to determining whether to use CTP performance. If digital proofing is not done well, it will completely lose the cost savings and efficiency that CTP equipment should have. ability. Nowadays, digital proofing + CTP technology + digital workflow system has formed a complete digital pre-press plate making solution.

With a digital workflow system, operators can send a prepared document to different terminal devices according to the purpose, which constitutes the basic framework for digital printing.

Digital proofing, CTP work together to achieve perfect color

Digital proofing is an analog print effect. As a customer's signature and standard for printing, the ideal goal for digital proofing is to be as close as possible to printing. In reality, most high-end color ink-jet printing systems use more than 6 colors of ink, and their color gamut is wider than the color gamut of an offset printer. Using a wide color gamut to simulate a narrow color gamut is, in principle, achievable. But to make the colors of these two different color gamuts be consistent, it is necessary to use color management software to establish a connection between two color gamuts. The method is to establish the ICC profile files of various digital proofing equipment and printing machines, as well as the dot compensation curves of CTP equipment, in order to achieve the matching of two color gamuts as much as possible.

Steps for implementing color management in the digital proofing process:

The first step is to create the ICC profile of the offset printing press and use this file as the print source ICC file for the entire system.

The second step compares and adjusts the printing effects of the standard printing proofs and the output plates of the CTP equipment to obtain the dot compensation curves output by the CTP.

The third step is to use the CTP output dot compensation curve to reprint the plate and reprint the standard proofs.

The fourth step is to use a spectrophotometer to test the newly generated printed standard proofs, and the obtained data is generated using a color management software to print a printed ICC Profile;

Finally, compare the color and gradation reduction of digital proofs and printing proofs, measure the color difference between printed proofs and digital samples, and use the software's “selection correction and cycle correction” function, after many corrections, the color of the two proofs will be the same. purpose.

After such adjustments, digital connections can be established between digital proofing, CTP equipment and printing presses, so that digital proofing can be more closely related to the actual effects of printing.

Digital proofing technology is not developed for CTP, but with CTP technology, digital proofing is bound to be used. Digital proofing and
Together, CTP technology forms the key link between prepress and printing, and it also becomes a necessary path for the development of digital printing technology. And in the continuous development, these two kinds of technologies also continue to promote each other, and constantly achieve new beyond.

Digital printing workflow

First of all, after receiving the customer's digital manuscript, the RIP and PDF file editing process of the image raster processor form a PDF file and layout conforming to the customer's requirements, and then transfer the file through the digital proofing software to the digital proofing machine for proofing, and finally the digital sample. Hand over to the client for the sample. This will be used as a production standard.

Second, the customer passes the PDF file processed by the CTP software to the inside of the CTP device after the sample is signed. The CTP-controlled laser exposure apparatus directly exposes the plate material and forms a CTP plate, which is then delivered to the printing press.

At the same time when the CTP plate is formed, the CTP system connects the CTP production data directly to the printing machine connected to it through the CTP and printer connection interface software, and various types of data of the printing plate, including ink data and fountain solution data of each zone Directly passed to the printer control system, the control system directly sets this data to the ink supply system and dampening system of the printing press, and completes the printer settings to ensure that the color of the finished product is consistent with the digital manuscript, thereby realizing the CTP. Automatic ink supply connected to the printer.

Finally, after the customer configures the CTP system, he must perform CTP system debugging. This requires the cooperation of all parties to complete. In addition to CTP system operators, printers are also required to debug personnel. Therefore, the process is relatively complicated. In addition, paper, ink, blankets, fountain solution, and other consumables are different, and each printer's dot gain rate is not the same.

The debugger of the printing press needs to form a halftone tone curve according to a certain ink, paper, blanket, dampening fluid, etc., and the curve must be fed back to the CTP system as a correction curve to obtain the CTP linear curve and the digital proofer setting curve. A new curve is comprehensively formed to guide the CTP system to generate CTP plates, so as to achieve a 100% fit of printed products and digital proofs.

In a nutshell, if a customer submits an electronic document at a point that is 20% of the network, then proofs made by digital proofers are also
20% outlets are 20% outlets on the finished product. Thanks to the use of the CTP system, a digital process for the entire printing process is realized, so dot reproduction can be achieved from 1% to 99%.

Because the intermediate process is completely completed by the CTP system, there is no process transfer process. At the same time, since the laser directly generates the printing plate, the number of printing screen lines can reach 250 lpi or even 300 lpi. Therefore, compared with the traditional printing process, the printing quality and efficiency are improved.