Printing Screening Process Talk - FM Networking (2)

2. Eliminate screen angle

The elimination of the pattern of rose spots reduces the possibility of print shops obtaining corner patterns and relaxes the requirements for strict registration. Misaligned and miscalculated FM networks are also unlikely to produce moire. However, in theory, it is still possible to produce the motif moire.

The FM network will not cause a neutral color cast or rainbow when overprinting is inaccurate, and the AM network will not generate a moire pattern effect due to overprinting. The overprint of the FM network printing is not as perceptible as the AM screen, but the color part will not be affected.

3. Frequency level in the FM network

The traditional calculation methods for determining gray levels are no longer suitable for FM networks. In an AM network, the positioning accuracy of the teletext recorder and the number of screen lines together determine the number of laser spots in the halftoning unit. In the FM network, regardless of the positioning accuracy of the graphic recorder, the basic printing dot size is consistent, and will not change until merged with its surrounding dots. The problem of grayscale becomes less and less attention, and how much detail can be reproduced becomes a crucial issue related to the resolution of the telegraphic recorder and the resolution of the scan.

4. Input sampling

Comparing the same image file printed using the AM and FM network, the FM network image can provide better details. Therefore, the FM network uses the lower sampling frequency to obtain the same level of detail as the AM network.

The halftone method of the AM network prints a large number of dots and has a large net distance. The method of converting a near continuous tone scan image into an amplitude modulation network is to discard details and evenly divide into halftone dots. With a few scan pixels forming a halftone dot, the ratio of scanned pixels to halftone dots is usually 4:1.

In the FM network, more details can be transferred to the screen. The ratio of scanned pixels to printed dots is much lower than conventional screening. Manufacturers claim that the ratio of scanned pixels and printing dots is 1:1 to obtain satisfactory image quality. However, most users say they use the same scanning resolution as a regular image.

The FM network allows more details to be reproduced, and for very high-quality jobs, even higher scanning resolution than the usual AM screen scan resolution can be used to further increase the detail.

5. FM network and high-fidelity color

The FM network is an ideal way to expand the print color space. Several color spaces have been defined for printing that use more than four primary colors. Additional colors are generally horizontal, green, red, and purple. Two or three of these colors are usually used in combination with the traditional CMYK. Additional colors can generate more dynamic colors with a wider range and better contrast.

Since any fifth or additional overlay screen in conventional screening can cause graining with other colors, the use of these extended color gamuts in primary color images has limited traditional screens. An ink overprint angle of less than 30° produces a perceptible moire pattern, which limits the number of screening colors in any area to no more than four. (There are only three possible angles when the screen angle is 30° apart, with the exception of the yellow version. The yellow plate is only 15° from the nearest screen in color separation, because the yellow is very bright, so the generated moire is not noticeable). There is no angle in the FM network and no wrinkles will occur. The use of FM nets can be overprinted, and any number of colors need not be worried about the quality degradation due to the moiré. The FM network also eliminates angled screens. Due to the randomness of the screen orientation, it is possible that no moiré appears. Therefore, any number of colors can be overprinted without moiré.

6. FM screening and waterless printing

The dot expansion of waterless printing is 5% to 10% smaller than that of the conventional lithography, so that finer screens and higher ink densities can be reproduced. Some printers used 600 lines/inch of conventional halftone screen printing with good results. However, waterless printing presses are very expensive, and they are very demanding for the operators. The latitude is very small, and the ink-water balance is difficult to guarantee. In particular, expensive printing plates and inks are required.

The FM network uses traditional printing presses, traditional plates, and inks to produce the same level of detail and lifelike color.

The use of a frequency-modulated network on a waterless printer can yield outstanding results. Outstanding dot-spreading networks are printed on small, water-free offset presses with dot gains. Both systems can obtain clear, vibrant colors and more details, and the combined effects increase exponentially.

The FM network can achieve fine image detail without the use of a waterless offset press, and ink balance and printer maintenance are not very difficult. Therefore, FM network can be used as an alternative to non-horizontal printing, but it can be used in combination with waterless offset printing to obtain more advanced printing quality.

(to be continued)