Screen soft proofing to achieve technical details

Screen soft proofing to achieve technical details

In recent years, with the wide application of CTP technology, continuous development and improvement of display technology, color management technology, digital technology, and file exchange format and network technology, soft proofing technology has obtained unprecedented development opportunities, has become more mature, and began to be applied. To the production area. Soft proofing is a brand-new proofing method. It has the advantages of fast proofing, convenience, and low cost. It attracts more and more attention. Especially, it can realize the remote proofing function with the advantage of the network. Therefore, soft proofing not only realizes the so-called concept of "What You See Is What You Get", it also brings about a more effective communication method, a more effective process and production management concept.

The basic principle of soft proofing

Soft proofing is also called soft proofing on the screen. It is a proofing method for simulating display output on a monitor. It performs color correction and color management on the monitor to achieve the same display effect between the monitors, and at the same time, the colors displayed on the monitor are consistent with the color reproduction effects of the printed products. It has the advantages of being intuitive, convenient, quick and flexible, cost saving, and improving production efficiency.

The basic requirement of the screen for soft proofing is that the display can accurately and stably simulate the color of the print. This requires that the display has a wide enough color space to cover the gamut that the printer can render. Such high requirements are still more difficult for ordinary displays. At the same time, because the color reproduction principle of the display and the print proofs are different, the observation conditions are also different, so the human eye will also affect the color perception of both. Thus, soft proofing of screens is still lacking in the reproduction of metallic colors, spot colors, and fluorescent colors.

The soft proofing process requires two color space conversions: one is the conversion of the source file color space to the target output device (printer) color space; the other is the conversion of the target output device (printer) color space to the display color space.

The entire soft proofing process can be broadly divided into three phases: first, the display and the press are calibrated to generate the characteristic files of the display and the printer; secondly, the characteristics file of the press is edited so that the standard file can be displayed on the display as much as possible. Consistent with the printing effect; thirdly, the printing press is adjusted during printing so that the print reproduction effect of the image is consistent with the display effect on the display to which the display and the printer profile are applied.

Key Techniques for Soft Proofing

In general, the realization of the ideal screen soft proofing effect must be based on high-quality displays, with mature color management techniques as the key, and precision measurement 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 generally used. The structure principle of the CRT display is that the electron gun is composed of a filament, a cathode, and a control grid. After being energized, the filament is heated, the cathode is excited, and the electron current is emitted. The electron flow is accelerated by the inner metal layer with high voltage, and is focused by the electron transmission. The fine electron beam hits the phosphor screen, causing the phosphor to emit light. R, G, B three-color phosphor dots are lit by electron currents of different proportional intensities to generate 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 alignment direction of the liquid crystal molecules changes, so that the R, G, and B color filter membranes cooperate with the liquid crystal molecules to make the display color. Its main parameters include the viewing angle, brightness, and response time. Shows pigments.

The precondition for 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, and the resolution should not be lower than 1024 x 768 dpi. At the same time, the color of the monitor that requires soft proofing is required. The scope of the domain must be larger than the range of the printing color gamut to be simulated. This is the basis for guaranteeing the complete and accurate reproduction of the printing color gamut. 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 advantages of low power consumption, low radiation, high color stability, and continuous declining prices of liquid crystal displays, liquid crystal displays have gradually become mainstream displays used in soft proofing. The current high-end display manufacturers mainly include Apple, Japan's EIZO, Barco and Sony Corporation.

2. Color management technology
Color management is a technique for correct interpretation and processing of color information. It is a method of converting the color data of an image from one color space to another on the premise of ensuring the minimum color distortion so as to ensure the color of the same image. The appearances shown in the input, display, and output processes match and match as closely as possible. Color management is generally divided into three processes: device calibration, characterization, and color conversion. The color management system uses the CIE Lab color space as the reference color space, and records the characteristics of the input device or the output device color with the feature file, and uses the application software and third-party color management software as the user's color control tool.

Screen soft proofing is based on color management. It realizes the characterization of displays, printers, and other devices, and realizes the mutual simulation conversion between the color gamut of the monitor and the color in the printer color gamut. The key to proofing. But screen soft proofing is not just about the color management of monitors and printers. It must be based on comprehensive color management. It should perform color management on all aspects of the printing process so that the color of the entire printing process is unified. Reach the screen soft proofing effect.

1 monitor calibration

The calibration of a display mainly refers to the testing and adjustment of the display to make its characteristics conform to the characteristics of a certain state of the device, or to generate new device features that conform to the current working state.
The calibration of the display first regulates the placement environment and lighting conditions of the display to ensure the accuracy of color reproduction. Secondly, it is necessary to ensure that the calibration of the display is performed under a stable working condition of the display, that is, sufficient preheating is performed before calibration. Thirdly, when correcting the display, the correct setting of the parameters is the most important. The gamma value, white field color temperature, brightness/contrast, and other parameters should be set reasonably according to the type of the display, the current state, and other conditions; The monitor hardware and color rendering performance will fluctuate over time, so the monitor should be regularly calibrated.

2 printing machine calibration

The soft proofing of the screen is ultimately to achieve the display effect of the image on the display in accordance with the reproduction effect of the printed matter printed by the printing press. Therefore, only the display is calibrated, and the display that meets the requirements cannot guarantee the final quality of the soft proofing of the screen, and must be printed. Machine for calibration.

The key control parameters of the printing press mainly include printing pressure, printing speed, ink balance, and register control. These parameters can be obtained by measuring the color deviation, solid density, dot gain, overprinting rate, and printing contrast of the printed test proofs. By analyzing these parameters of the test sample, the press operator calibrates the press until the printer's performance reaches the normal print level, and then prints the test sample again, measures the relevant data, and produces the presses. ICC file. The production of printing test samples should fully reflect the current working status of the printing machine, and it is better to use the existing standard color standard, such as IT8.7.3 color standard file.

3. Measuring instruments and software

In addition to having a display and a certain color management technology, the entire soft proofing process must also be equipped with sophisticated measuring instruments and well-functioning software to ensure the accuracy, accuracy, and softness of the measured data. The effectiveness and robustness of the proofing function.

At present, there are many kinds of commonly used color management software. The function and usage of each software are similar. The effect of color management is basically the same. Commonly used specialized equipment characterization software includes Heidelberg, Gelling, X-Rite, and Net. The screen companies provide a series of software, such as Heidelberg's ViewOpen, PrintOpen, X-Rite's ColorShop, Monaco Optix, Gelingda's Gretag ProfileMaker and so on.

Commonly used measuring instruments mainly include X-Rite DTP94 screen calibrator, X-Rite DTP92 spectrophotometer, X-Rite 530 densitometer, X-Rite DTP41, and Eye-one Pro spectrophotometer.

At present, more commonly used software for soft proofing is also available. Soft proofing software certified by SWOP International includes ICS Remote Director, Creo Synapse Insite, KPG Matchprint Virtual, and Dalim Software's DiALOGUE software.

The summary screen soft proofing technology plays an increasingly important role in the color management system of printing production. The realization of soft proofing of the screen is benefited from the continuous development of the display technology, thanks to the continuous improvement of color management technology, benefiting from The continuous improvement of matching measuring instruments and software. Effective screen soft proofing not only provides more valuable information for printing, assists the printing operator in effective color management, but also facilitates communication with customers, enabling customers to understand the production status in a timely manner and view the production process at any time. , Modify mistakes, avoid waste and repetitive work, reduce production costs and improve work efficiency. Printing companies should learn more about this technology, and then apply this technology in actual production to innovate the company's printing process and service model, and then comprehensively improve product quality and enhance the competitiveness of enterprises. The soft proofing of the screen completes the digital workflow and is in line with the development of modern printing technology, and there will inevitably be broad prospects for development.