Comparison between FM and am screening of the hott

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Comparison between FM and am of digital processing technology

in today's complex full-automatic prepress workflow, the hot topics discussed mainly focus on PDF, JDF, XML, CMS, ICC and other issues, and processing is no longer the most concerned technology of prepress experts. However, recent developments have shown that addition, as well as other ways of forming points, is still the most concerned issue for prepress workflow and output system manufacturers and sellers. The advantage of optimization plus technology is to bring more vivid prints, clearer details, no moire and the stability of the process to printing enterprises, and those enterprises that ignore this technology miss a very important production control tool

first, let's review the development of digital addition technology. It evolved slowly from the glass and contact screen used in the formation of simulation points. From the early stage of offset printing technology, printing process experts have been experimenting with point shape, angle and number of lines, hoping to optimize the effect of printing and control the process. Digital addition provides us with a possible way to form points in a physical way, so that the constraints on technology are no longer a problem

when DTP (desktop publishing) appeared, the early postscript Rip can realize four-color and multi-color digital addition, but its quality is lower than that of analog addition and digital addition of special high-end color system. Experienced prepress operators may remember the extensive and intense discussion on "plus" in the late 1980s. Later, revolutionary changes have taken place in the composition of optimization points, providing more options for adding angles than postscript level 1. At the same time, prepress equipment manufacturers began to pay attention to postscript rip and apply their rich knowledge to desktop publishing systems

the real revolution is to adopt FM or random addition, although it is not a new idea. In the 1980s, it has been applied to the digital printing process with low requirements for dot quality. It does not use dots of different sizes to simulate different continuous tones, but uses the interval between dots of the same size and relatively small to reproduce the tones. Fm/random plus was launched at the height of the Canadian war and received a lot of advertising and expectations. Since then, the traditional addition method has been named am (amplitude modulation) addition to distinguish it from FM addition

compared with am, FM has the advantage of clearer effect, because tiny points can produce more tones; Ensure that there is no moire between colors and patterns, so as to make the printing process more stable. However, before applying FM plus to a wider range of non specialized applications, it encountered many obstacles. The disadvantages faced in the early 1990s are: it is very difficult to process in the computer to film (CTF) environment, and there is no exposure range of the printing plate; Grain pattern will be produced in the gray middle tone and flat area; And it is difficult to compensate the color difference by using the method of ink thickness change on the printing machine. The operators who used this method in the early stage can rarely persist in using it all the time

in the past ten years of plane control test blocks, a small number of prepress and printing enterprises have begun to tacitly cooperate to use FM processing technology to produce high-quality prints by adding accessories. Those art books and high gloss Catalogue Products with objects prone to moire, such as textile images, pupil of speakers and architectural design, have benefited from FM plus technology and become a technology they are happy to use

because CTP technology simplifies the process, it plays an important role in the recovery of FM plus technology. In addition to film, dust and registration problems have become some factors that hinder the development of FM technology. After using CTP technology, there is no need to consider the film edge (thickness) or dust particles too much, so smaller FM points (usually 12 to 30 microns in offset printing, and 70 microns in flexo printing and newspaper printing) can be formed directly on the printing plate. Another advantage of CTP technology is that harder dots can be formed on the thermal plate to obtain better printing effect. Particles composed of laser beams can form predictable additive points in imaging and printing. Any point edge composed of unfixed layers of the residual printing plate will not form an irregular printing effect

Creo strongly recommends the use of Turbo or squarespot plus technology, which takes another step forward in hard spot quality. This technology adopts a higher resolution in the main scanning direction (exposure roller circumferential direction) than in the secondary scanning direction (roller upper direction), so as to improve the accuracy of adding points. Compared with the traditional point imaging (2400x2400dpi) technology with the same size, the addition of points composed of more particles can obtain higher resolution effect (9600x2400


Heidelberg applied this technology to their CTF imager several years ago. Creo combines this precise point composition, its staccato plus technology and consulting services to revive FM plus technology again. It advocates controlling in-machine profits, including reducing the amount of ink, obtaining higher color stability and making it easier to balance ink and water. Better printing process stability has gradually shifted offset printing from 65 extra lines per inch of newspaper printing to lines per inch (40-44 lines per cm). In commercial offset printing, the number of lines added is increased from 133 LPI (54 l/cm) to 175 LPI (70 l/cm), and the printing with very high quality requirements can even reach 200 LPI (80 l/cm)

a method similar to FM to replace am processing technology is to use a very fine screen for processing. This method has been widely popular in Japan, and is widely used by many professional printing enterprises in the Western Hemisphere. This method usually adopts LPI or even higher line number to optimize the printing effect, and realizes clearer and finer effect through high-density ink. Ma song, an analyst at Guolian securities, who is the same as FM, said that the breakthrough of ultra-high number of lines met problems, such as harsh process conditions and the need for high-resolution scanning to generate maximum profits

in many places in Europe and the United States, on April 27, 300 dpi scanning and a moderate false light mask are often the default settings, while in Japan, the scanning standard is set to 350 DPI and a slightly higher level of unclear mask to meet the requirements of a higher number of lines. Higher image resolution is related to the number of ultra-high lines, that is, it can produce more gray levels

for 4000 DPI of ultra-high plus line, compared with 2400 or 2540 DPI, which is more commonly used in am and FM plus in the western world, the imaging process is greatly slowed down. Fuji company has proposed a traditional angle adding co res method, which can be comparable to the image effect with relatively high resolution. Thus, a 1219 DPI image can achieve the effect of 175 LPI. Or you can get the effect of 300 LPI from a plate making machine with a slightly lower image resolution. So far, this technology is still limited to the application of Fuji's cellular rip and plate making machine. The most direct advantage is that there is a leap in the overall production volume, because less data needs to be processed, and there is no need to change the operating habits of the printing machine, because the screen angle and point are completely consistent with the original

the disadvantage of the hybrid addition method is that interactive masks are required on high-end workstations, such as screen's taigapress, so it has high labor intensity and is only suitable for high-value printing projects. For packaging applications, the printing method of more than four colors is usually used. For the rougher number of lines added in flexo printing, Barco and artwork systems have developed the corresponding mixed adding method, which can not only avoid the appearance of moire, but also produce more details in the brighter and darker areas, and can be used for clearer and more saturated printing. This mixed addition method can provide FM details and continuous tone reproduction of bright and dark areas, and will not affect most flat and intermediate tone grainy graphics and text, because these are achieved through AM addition

in the field of newspaper printing, Agfa has just completed the test of the hybrid plus technology sublima, which has been tested in Norway. FM cristalraster points are used in some areas, and am ABS plus is used in the middle tone part. Screen has recently introduced a new hybrid addition technology spekta, which enables its thermal CTP imager to obtain the best quality. Spekta addition technology effectively combines the advantages of FM and am addition methods in point composition, color mixing, moire and easy operation compensation on the printer

like other hybrid addition methods, spekta adopts FM addition in the replication area of% and%, and adopts am dot addition in the range of%. Because all points are randomly distributed within the total point range, there is no restriction on adding angles between different colors, so there will be no moire problem when mixing colors. Compared with other high-line adding methods, spekta can provide an optical effect similar to 300+lpi, and there is no limit to productivity, but 2400 DPI adding is used in standard image setting areas such as 175 LPI (70 l/cm)

generally, adding text to the image will achieve better results, such as wine labels and maps. Using screen's spekta plus technology can eliminate obvious rose spots and moire. Together with screen taiga and trueflow, it provides users with a unique platerite thermal imager, which is a general and most suitable plus solution. New technologies related to thermal CTP imaging technology can now produce clearer and more reproducible point quality. Based on this, prepress customers are constantly looking for the best addition mode to obtain the maximum productivity, so as to achieve the best replication effect in the easiest way. In the process of printing and reproduction, dot is undoubtedly the most important problem. The organic combination of AM and FM technologies will produce better results

videga technology now, the screen combines regulator amplitude plus and frequency modulation

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