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Analysis of AM points and FM points

point angle refers to the angle between the point arrangement line and the horizontal line, which is generally subject to the angle measured counterclockwise. The longitudinal and transverse shapes of chain points are different, and the two columns with a difference of 180 are completely consistent, and the point angle is 0 ~ 180. When the difference between a square point and a circular point is 90, the angle is the same, so the angle is from 0 to 90

generally speaking, when the angle difference between the two points is 30 degrees and 60 degrees, the overall interference fringes are relatively beautiful; The second is the point angle difference of 45 degrees; When the angle difference between the two points is 15 degrees and 75 degrees, the interference fringes will be obvious, resulting in obvious moire fringes (moire), which is very detrimental to the beauty of the image

take the square dot as an example. From the perspective of visual effect, the 45 dot angle produces the most comfortable and beautiful visual effect, which is stable and not rigid. Therefore, for monochrome printing, the 45 dot angle is usually used, which is a new topic. Although the point angles of 15 and 75 are not very stable, they are not rigid. The point angle of 0 has the worst visual effect. Although it is stable, it is very rigid. Therefore, the visually weakest yellow version is usually used for 90

amplitude modulation point and frequency modulation point

according to the addition method, points are divided into amplitude modulation point (AM screening, which represents the image level by the size of points, the point spacing is fixed, and the point size changes) and frequency modulation point (FM screening, which represents the image level by the density of points rather than the size of points). Most of the previous descriptions of points in this paper are for am points. Here are some characteristics of FM plus

the full English name of FM plus is frequency modulation screening

the point size of the screen adjustment point is fixed. When the resolution of the output device is 2400dpi, the diameter of the minimum point is about 10.5 microns (i.e. 1/24 and 00inch of products such as structural parts required for lightweight). It shows the order by controlling the density of points. The points in the bright part are sparse, and the points in the dark part are dense

at present, the frequency modulation plus technology adopts the random addition of first-order functions, with equal dot sizes and random dot spacing changes. Photo image processing is the deposition of halogen particles (0.m) with different sizes and distances to form tones or colors. Therefore, at present, some institutions have been studying the simulation of photo effects in principle. That is, if the second-order function is used to add randomly, the distance and area of the dots can change randomly. Then, the second-order function addition is very similar to the original photo in the mechanism of expressing the tone, and the replica will be more authentic, almost completely close to the effect of the photo image level. Of course, the calculation of random addition of second-order functions is larger and more complex, and the current printing equipment and condition estimation are difficult to meet the requirements

fm screening has the following advantages: no collision; The generated points are small, which can show more details Tone jump to eliminate midtones The registration problem will not affect the color balance

fm screening has disadvantages: light level and peace are easy to produce roughness and graininess The point density of the middle tone is very high, and the point expansion rate is difficult to control; Need high-precision printing equipment and harsh printing conditions; The film output requires stability, and the reproducibility and sharpness of fine dots are higher than those of AM dots When printing, the light level is easy to lose, and the deep level is easy to block

at present, with the development of printing technology, there are also points of am/fm hybrid type. For example, with the continuous development of the material industry, the cibidaga technology, which combines the advantages of the traditional am and FM technology, can avoid moire and broken lines

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