The most popular digital color prepress proofing s

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Digital color prepress proofing should be gradually promoted

in recent years, color DTP system has been widely used in, publishing, advertising, printing and other industries and departments. It can not only organize and arrange color newspapers, magazines, books and periodicals in various formats, but also handle various exquisite color printing publications, replacing many traditional printing operations, such as graphic input, color separation, grouping, decoration, processing and other processes and technologies. In the advanced digital color image and text processing system, the processed finished products have to pass the traditional color proofing before batch printing. It is understood that there are not many digital color proofing in Hong Kong, and the thermal insulation effect of foreign printing technology is equivalent. Countries with more developed technology also retain traditional color proofing. Then, in today's rapid digitization of color prepress operations, why do we keep and use traditional color proofing for a long time? Why can't digital color printing thousand proofing be widely used in China

the development trend of digital color prepress proofing

prepress proofing is for all aspects of design, printing and customers. From the proofs, we can see the effect of the final batch printing, especially the color effect. In the traditional color proofing process, four-color color separations are first used to make proofing plates, and then proofed on the offset proofing machine. The proofing sheet can be printed in batches after being designed, printed and approved by customers in all aspects. If you are not satisfied with the proofs, you can remake them until you are satisfied. At this time, the proof sheet is called "contract sample sheet", which becomes the common basis for the recognition of the printing factory and the customer. Because the traditional printing uses the same four-color color separations to sun the printing plates for proofing and batch printing respectively, the effect of proofing and batch printing can be very close, which is also the most important advantage of traditional proofing. Below the glass transition temperature, amorphous polymers are in the glassy state, but the development of things is not absolute. Traditional color proofing is also more affected by subjective factors. Because the environment and conditions of proofing are different; The drugs, ink and paper used are different; The technical level and work experience of proofers are different. The same four-color color separations are proofed in two different offset proofing departments, and their effects are also different. This is also the deficiency of traditional color proofing

traditional color proofing must have four color separations, which are used to sun proofing plates; Digital color proofing does not need four-color separations. Color images and words are processed by computer and directly output to color proofing machine for proofing. At present, there are many kinds of color proofing machines popular in the market, including thermal sublimation, laser, wax spraying, inkjet, etc. some of them have high printing accuracy and bright colors, but they are not necessarily suitable for prepress proofing. The most important requirement of prepress proofing is that the proofing sheet can reproduce the color of the original, and match with the CMYK color characteristics of batch printing, so that the color of the finished product of batch printing is as consistent as possible with the proofing sheet. In short, the most important thing in prepress proofing is the color effect that matches the original and printed matter. Therefore, the digital color printing system used for prepress proofing is specially equipped with color management software, which can automatically or by the user to adjust the appropriate color effect

with the increasing demand for printed matter, many color plate making and printing design departments, advertising companies, output centers, newspapers, publishing houses, etc. have established their own color systems to process the printing layout by themselves, and the demand for prepress proofing is increasing. Designers and customers hope to see the layout effect in time. Traditional color proofing has been difficult to meet the requirements. At present, some digital color prepress proofing systems have been able to achieve accurate color matching, and they are cheap and applicable. It is estimated that they will be popularized among users soon. Therefore, printing houses should also face the reality of digital color prepress proofing technology and accept digital color prepress proofing in traditional offset printing. In particular, with the development of CTP direct plate making technology, there is no film imaging in the whole process, so the traditional color proofing method can no longer be used, and the digital color prepress proofing method must be used. Therefore, the development of applicable digital color prepress proofing technology and products has become a necessity for production. The promotion of digital color prepress proofing in production will raise many problems:

1. Self bounded colors are extremely complex, which can not be completely expressed with basic colors RGB or CMYK, and it is more difficult to reproduce the original colors of nature

2. RGB and CMYK color systems do not overlap. Colors that can be expressed with RGB may not be expressed with CMYK system, and colors seen on the display screen may not be printed or printed on paper

3. Due to different color characteristics of different devices, the color of the same image will be different

4. even the same device, due to different environments, or the aging of old components that have brought higher value to our customers, shows different colors to the same image

generally speaking, the color management system is established to solve the above problems. The color management system mainly includes the following contents and functions:

1. Color conversion. For example, the conversion from RGB color space to CMYK color space is completed by computer

2. device profile. It indicates the characteristics and ability of color reproduction of a device, and adjusts the transfer and conversion of calibration color according to this file, so that the color can be accurately reproduced. However, the color management software can work correctly and effectively only if the user correctly defines the documents that reflect the characteristics of the device and provides the characteristics of the ink, paper and media used

many tasks in color management need to be completed by users, and there are certain difficulties. For example, the device should be calibrated regularly and the reproduction characteristics of color should be described. Sometimes, the format of the color reproduction characteristic description file of the equipment of various manufacturers is different, and some equipment does not have the characteristic description file itself, which needs to be established by the user through customization. Some experts estimate that about 10% of users can use the color management system, and a large number of users deal with color problems based on their own practical experience. In order to avoid the difficulties and troubles encountered in the use of color management systems, some color management systems are designed for certain specific equipment, specific inks and media, and try to bring convenience to users in use. Next, take the color management software radiance built in rip of Huakang technology as an example:

1. The color seen in nature is a complex mixture of all color visible spectra. Radiance first takes out tens of thousands of colors from the spectral range of 400~700nm visible light, and then outputs high-quality color proofs from high-quality image Phototypesetting under specified conditions after computer processing, Then 3M (matchprint, fujicolorart, DuPont cromalin, etc.) recognized by the printing and publishing industry as a standard is used for color correction. After the correctness of color proofs is verified, these color proofs are measured with a spectrometer, and these data are transmitted to the computer as a "source header file".

2. The "source file" in the computer Output from the color output machine to be corrected, then test each color with a spectrophotometer, compare the data output by the output machine to be corrected with the data corresponding to the source file, and establish a conversion table by the difference, which forms a color conversion correction table. Use this table to calibrate the documents of the output machine, and the color difference can be corrected

3. because the output machine to be corrected is different from the ink and paper used, the measured spectral characteristics are also different, so radiance's color correction is right for a specific combination of ink and paper media, and is carried out on some specific output devices, and the color can be accurately matched repeatedly

4. The above color calibration is carried out in the factory, which is a complex work, and it is difficult to complete by users. Radiance liberates users from the complex work of defining and establishing device description characteristics and color calibration curves. It is very convenient for users to realize "just press the key". However, users should remember that their color management is for some specific output machines, inks and papers

concept change and technical preparation

digital color prepress proofing is a new technology, which has not been widely recognized by the printing and publishing industry in China so far. As the digital color prepress proofing system is becoming more and more accurate in color matching, some digital color prepress proofing systems are cheap in price, low in cost, fast and convenient, and have great market development prospects. All parties concerned should be prepared conceptually and technically. Non traditional printing departments, such as advertising, design, newspapers, etc., will first use digital color prepress proofing system. Some units such as printing technology magazine, China Standard Publishing House, Xinmin publishing house, etc. are already in use. The light bridge using Epson 3000 printer has been launched in Hong Kong and abroad, and will be launched in the mainland in the near future. It can conduct digital color prepress proofing on A2 format. HP design jet series or ENCAD Nova jet series proofing machines can be used for larger than A2 or full format

digital color prepress proofing system generally does not output traditional amplitude modulation points, such as thermal sublimation output continuous modulation, and inkjet set output frequency modulation points. If the design and plate making department has used the digital color prepress proofing system, the traditional printing industry will also change the traditional concept and take the initiative to adapt to increase the printing source. Under the impact of high technology, especially under the condition of market economy, economic interests are a very important factor. New technology and traditional technology should adapt to each other, and traditional industry unilaterally wants to go. It may not be appropriate for new technology to meet the original process

relevant colleges and universities, science and technology development departments should cooperate with printing plants and actively participate in the development and introduction of new technologies. Introduce the color management system according to the national conditions of our country, or design the color management system of our country separately; Comparative tests can also be carried out to convert the relevant parameters of digital prepress proofing to the parameters of traditional printing process, so as to meet the requirements of traditional process; It can also help the printing department to learn and master advanced color management knowledge and technology, change some traditional concepts and operating processes, and truly realize the color management of digital competition, which is divided into two stages

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