Digital proofing, as the name implies, is based on the digital prepress system. In the prepress design and production process, the page graphic information is processed according to the printing production standards and specifications. The digital output system is used to directly output the color samples. The originals directly output printed proofs. The most commonly used digital printing technology today is to use a large-format color inkjet printer as the output device to directly output and print color proofs, and use this as the basis for the final printed print and the same print.
CTP technology is short for Computer to Plate. In short, this technology is to output the graphic information completed by the pre-press design and output directly to the printing plate through related equipment. Computer direct plate-making technology is a general term for a large class of technologies. Whether it is offset printing (offset printing), gravure printing, embossing printing or screen printing, there are corresponding computer direct plate-making technology. However, in the actual printing industry, CTP technology generally refers specifically to the computer-to-plate making of offset printing. The CTP technology mentioned in this article also refers specifically to computer-to-plate for offset printing.
Digital proofing is dependent on CTP technology
Digital proofing and CTP technology are two technologies developed independently, but the common characteristics are destined to bundle these two technologies together. Especially the application and popularization of CTP technology has greatly promoted the development of digital proofing. As a technology, digital proofing can exist independently, but if CTP technology is to develop, it must rely on the help of digital proofing. The reason is very simple. The result obtained by CTP technology is a printing plate, but it is impossible to know the final printing effect by looking at the printing plate itself. Because the CTP technology eliminates the intermediate medium in the process of making a film-film, it is impossible to use the film for printing and printing like the traditional plate-making process. So how do you know what the final printed product looks like? There is only one method, which is to use digital proofing to complete proofing, signing and follow-up work. Some people may ask, is it not possible to use the CTP plate-making mechanism to directly proof on the proofer? In theory, of course it is possible, but in terms of cost, no one will do so. As a result, digital proofing has also become an essential assistant and assistive technology for CTP technology.
CTP technology + digital proofing + workflow software together constitute a complete digital pre-press platemaking solution.
Digital proofing
The digital proofing technology most used in the printing industry now uses large format color inkjet printers or large format color laser printers with very high proofing quality as the output device to print proofs. These devices are continuously adjustable output devices, although some manufacturers have tried to use color inkjet printers to simulate printed dots, but the effect is not very satisfactory.
In addition to the continuously adjustable digital proofing equipment, some companies have also developed "true dot" digital proofing equipment. The most representative equipment is Fujifilm's Final proof and Kodak's Approval XP proofer. But the price of such professional equipment is very expensive. Therefore, in the actual digital proofing production, the application of large format inkjet printers is more common. [next]
Similarities and differences between digital proofing and CTP technology
The commonalities between digital proofing and CTP technology are obvious. Digital proofing directly outputs proofs from digital files, eliminating the tedious link of film, printing and printing on the middle; and CTP technology directly outputs printing plates from digital files, also eliminating the need for film and printing. Whether it is digital proofing or CTP technology, it starts from a digital file and directly reaches the final result. What keeps the two together is a digital pre-press file that remains unchanged throughout the process.
But the words are simple, but they are far from being so simple. First of all, although the digital files are the same digital files, the output devices are different, and the output content is also different. Digital proofing equipment directly outputs color proofs to form color images; CTP equipment outputs printed plates with color separation dots. The two have different color gamuts, different forms, different materials, and different imaging principles.
In addition, the plate material exported by CTP is still a transitional product, and it needs to be printed on the machine before it can be converted into the final printed product. The transmission of the image information in the middle is difficult to achieve 100% consistency. Therefore, even if the color content expressed by the image information of the printing plate is completely consistent with the digital proof, the effect of the printed matter must be completely matched with the color proof of the digital proof , Its difficulty is very large. This is also the industry's most troublesome proofing and printing mismatch.
Digital proofing and CTP cooperate to achieve perfect color
Digital proofing is to simulate the printing effect, as a standard for customer signing and printing, so the ideal goal of digital proofing is to be as close as possible to printing. In reality, most high-end color inkjet printing systems use more than 6 colors of ink, and the color gamut is wider than that of offset presses. Using a wide color gamut to simulate a narrow color gamut is theoretically achievable. But to make the colors expressed by these two different color gamuts consistent, you need to use color management software to establish the relationship between the two color gamuts. The method is to establish the ICCprofile file of each digital proofing device and printing machine, and the dot compensation curve of the CTP device, in order to match the two color gamuts as much as possible.
In this process, the common method is to first make the ICC characteristic file of the offset press; then use this as the printing source ICC file of the entire system, compare and adjust according to the standard printing sample and the printing effect of the CTP equipment output printing plate, and draw CTP output dot compensation curve; after determining the CTP output dot compensation curve, re-output the printing plate after determining the CTP output dot compensation curve, and reprint the standard sample; use a spectrophotometer to perform the newly generated printing standard sample Detection, the obtained data uses color management software to generate printed ICC Profile files; finally, compare the color and tone reduction of digital proofs and printed proofs, measure the color difference between printed and digital proofs, use the software to select color correction and cycle correction functions, After multiple corrections, the purpose of achieving consistent color of the two proofs is finally achieved.
After such adjustment, a digital connection can be established directly in digital proofing, CTP equipment and printing presses. Make the digital proofing more suitable for the actual effect of printing, so that the printing equipment can catch up with the color of digital proofing.
Digital proofing technology was not developed for CTP, but with CTP technology, digital proofing must be used. Digital proofing and CTP technology work together to form a key link between pre-press and printing, and also become the only way for the development of digital printing technology. In the continuous development, these two technologies are also constantly promoting each other, and constantly achieve new transcendence.
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