Screen soft proofing implementation technology in detail
In recent years, with the widespread application of CTP technology, the continuous development and improvement of display technology, color management technology, digital technology, file exchange format and network technology, soft proofing technology has obtained unprecedented development opportunities, has become increasingly mature, and began to apply To the production area. Soft proofing is a brand-new proofing method, which has the advantages of fast proofing, convenience, and low cost. It is more and more valued by people, especially its advantage of using the network to realize remote proofing. Therefore, soft proofing not only realizes the so-called "what you see is what you get" concept, it also brings a more effective communication method, a more effective process and production management concept.
The basic principle of soft proofing
Soft proofing, also known as screen soft proofing, is a proofing method that simulates the display of print output effects on a display. It performs color correction and color management on the monitor to achieve consistent display effects between the monitors, and at the same time to achieve consistent color reproduction between the color displayed on the monitor and the color of the printed matter. It has the advantages of intuitive and convenient, fast and flexible, cost savings, and improved production efficiency.
The basic requirement of the screen soft proofing on the display is that the display can accurately and stably simulate the color of the printed matter, which requires the display to have a wide color gamut that can cover the printing machine. Such high requirements are still relatively difficult for ordinary displays. At the same time, due to the different color reproduction principles of the display and the printed sample, and the conditions of observation are also different, the human eye will also be affected by the color perception of the two. Therefore, screen soft proofing is still lacking in the reproduction of metallic colors, spot colors, fluorescent colors and so on.
The soft proofing process undergoes two color space conversions: one is the conversion of the source file color space to the target output device (printing machine) color space; the other is the conversion of the target output device (printing machine) color space to the display color space.
The entire soft proofing process can be roughly divided into three stages: first, calibrate the display and the printing machine to generate the characteristic files of the display and the printing machine; second, edit the characteristic files of the printing machine to make the standard file display on the display as much as possible Consistent with the printing effect; third, adjust the printing machine during printing so that the printing reproduction effect of the image is consistent with the display effect on the display to which the display and the printing machine characteristic file are applied.
Key technologies for soft proofing
In general, the realization of the ideal soft proofing effect of the screen should be based on a high-quality display, with mature color management technology as the key, and precision measuring instruments and software as the guarantee.
1. Display technology
In the field of publishing and printing, CRT (cathode ray tube) type and LCD (liquid crystal) type displays are commonly used. The structure principle of the CRT display is that the electron gun is composed of the filament, the cathode, and the control grid. After the power is turned on, the filament heats up, the cathode is excited, and the electron flow is emitted. The electron flow is accelerated by the internal metal layer with high voltage, and is focused by the electron transmission. The thin electron beam bombards the fluorescent screen, causing the phosphor to glow, and the three-color fluorescent dots of R, G, and B are lit by electron flows of different proportions of intensity to produce various colors; the principle of the liquid crystal display is to use the physical characteristics of the liquid crystal. Under the action of the external electric field, the arrangement direction of the liquid crystal molecules changes, so that the R, G, B three-color filter film and the liquid crystal molecules work together to make the display color. Its main parameters include viewing angle, brightness, response time, Display pigments, etc.
The premise of the realization of soft proofing is that it must have a high-quality display, and the size of the cathode ray tube display and the liquid crystal display used must not be less than 17 inches, the resolution is not less than 1024 × 768dpi, and the color of the soft proofing display is also required. The gamut range must be larger than the printing gamut range to be simulated. This is the basis for ensuring that the printing gamut can be completely and accurately reproduced, and it is also a prerequisite for ensuring the feasibility and effectiveness of soft proofing.
Not all types of monitors can be used for screen soft proofing. In recent years, with the continuous development of display technology and the highlights of the advantages of low energy consumption, low radiation, high color stability, and falling prices of liquid crystal displays, liquid crystal displays have gradually become the mainstream display used for soft proofing. At present, manufacturers of high-end displays mainly include Apple, EIZO, Barco and Sony.
2. Color management technology
Color management is a technique for the correct interpretation and processing of color information. It is a method to convert the color data of an image from one color space to another color space on the premise of ensuring minimum color distortion to ensure that the color of the same image is The appearance in the process of input, display and output should be matched and consistent as much as possible. Color management is generally divided into three processes: equipment calibration, characterization and color conversion. The color management system uses the CIE Lab chromaticity space as the reference color space, records the color characteristics of the input device or output device with a characteristic file, and uses application software and third-party color management software as the user's color control tools.
Screen soft proofing is based on color management. It realizes the characterization of devices such as displays and printing presses, and realizes the simulation conversion between the color gamut of the display and the color gamut of the printing press. The key to proofing. However, the soft proofing of the screen is not only for the color management of the display and the printing press, but must be based on a comprehensive color management, color management of all aspects of the printing process, so that the color of the entire printing process is unified, so as to To achieve the effect of screen soft proofing.
â‘ Monitor calibration
The calibration of the monitor mainly refers to testing and adjusting the monitor to make its characteristics conform to the device characteristics of a certain state, or to generate new device characteristics that conform to the current working state.
The calibration of the monitor must first standardize the placement environment and lighting conditions of the monitor to ensure the accuracy of color reproduction; secondly, it must be ensured that the calibration of the monitor is performed in a stable working state, that is, sufficient warm-up before calibration; Third, the correct setting of the parameters is the most important when performing monitor calibration. It is necessary to set the gamma value, white field color temperature, brightness / contrast parameters and other parameters reasonably according to the type and current status of the monitor; The display hardware and color rendering performance will fluctuate over time, so the display should be corrected periodically.
â‘¡Printing machine calibration
Screen soft proofing is ultimately to achieve the same display effect of the image on the display and the reproduction effect of the printed matter printed by the printing machine. Therefore, only the display is corrected. Obtaining a display that meets the requirements cannot guarantee the final quality of the screen soft proofing. Machine calibration.
The key control parameters of the printing press mainly include printing pressure, printing speed, ink-water balance and register control. These parameters can be obtained by measuring the color deviation, solid density, dot expansion, overprint rate, printing contrast and other parameters of the printing test sample. Through analysis of these parameters of the test sample, the press operator adjusts the press until the performance of the press reaches the normal printing level, then prints the test sample again, measures the relevant data, and makes the press ICC file. The production of printing test samples should be able to fully reflect the current working state of the printing press. It is best to use the existing standard color standard, such as IT8.7.3 color standard file.
3. Measuring instruments and software
In addition to the display and certain color management technology, the realization of the entire soft proofing process must also have matching precision measuring instruments and fully functional software to ensure the accuracy, precision and softness of the screen data The effectiveness and robustness of the proofing function.
At present, there are many kinds of color management software commonly used, the functions and usage methods of each software are similar, and the color management effect is basically the same. The commonly used professional equipment characterization software mainly includes Heidelberg, Greenland, X-Rite, Net. A series of software provided by the screen company, such as Heidelberg's ViewOpen, PrintOpen, X-Rite's ColorShop, Monaco Optix, Gretag's Gretag ProfileMaker, etc.
Commonly used measuring instruments include X-Rite DTP94 screen calibrator, X-Rite DTP92 spectrophotometer, X-Rite 530 density meter, X-Rite DTP41, Eye-one Pro spectrophotometer, etc.
At present, there are many soft proofing software commonly used. SWOP internationally certified soft proofing software mainly includes ICS Remote Director, Creo Synapse Insite, KPG Matchprint Virtual and Dalim Software's DiALOGUE software.
to sum up
Screen soft proofing technology plays an increasingly important role in the color management system of printing production. The realization of screen soft proofing benefits from the continuous development of display technology, the continuous improvement of color management technology, and the The matching measuring instruments and software are continuously improved. Effective screen soft proofing can not only provide more valuable information for printing, assist printing operators to carry out effective color management, but also facilitate communication with customers, so that customers can timely understand the production status and view the production process at any time. , Correct mistakes, avoid waste and repetitive work, reduce production costs and improve work efficiency. Printing companies should know more about this technology, and then apply this technology in actual production to innovate the printing process and service mode of the enterprise, and then improve the product quality and enhance the competitiveness of the enterprise. The soft proofing of the screen improves the digital workflow, which is in line with the development direction of modern printing technology, and it will inevitably have broad development prospects.
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