FM network is another kind of network technology. Its characteristic is that the size of the network point is fixed, the level is expressed by the change of distribution density, the position of the network point is random, there is no concept of network line and screen angle, and the diameter of common screen dot is used to distinguish. Commonly used network diameters are: 20 (equivalent to 1% of the AM network 150 lpi), 14 (equivalent to 1% of the AM network 200 lpi) and 10 (equivalent to 1% of the AM network 300 lpi). Its advantages are: no net flower, delicate image, no moire, good reproduction of bright and dark tone, and lower resolution output. The disadvantages are: the duplication of the flat screen has a sense of sand, and the printing dots are enlarged very much. The dots of the entire tone increase more than 30%, and they are very sensitive to the printing pressure and the amount of ink and ink. A printing press needs a set of calibration data. Minor changes in printing conditions can affect the overall image tone. Poor printing processability is a fatal weakness of the FM network, and high quality is accompanied by high costs. Therefore, although the FM network has been popularized for many years, it has rarely been used practically, even in regions where CTP is widely used.
The advantages and disadvantages of AM and FM are summarized as follows (Table 1)
3) Hybrid Screen outlets
It's natural that the idea is to combine the advantages of AM and FM, and the Hybrid Screen has a spontaneous effect. This technology has undergone several generations of changes.
The first generation, FM screening and detailing, amplitude modulation and screening performance, has the obvious flaw between frequency modulation and amplitude modulation network, and the calculation time is very long. See (Figure 4).
In the second generation, FM radio was used to express highlights, and AM screening was used to represent midtones. The defect was that there were obvious traces between the FM and AM networks and the calculation time was very long. See (figure 5).
The third generation, network size, location, number are different, FM / AM and white, its flaw is the tone of the middle tone and flat screen. See (Figure 6).
In the dot-com technology has been the leading Agfa, in 2002 launched a breakthrough XM outlets: Sublima, a good solution to the quality of print, printing process and printing costs between the problems.