Formation and production mechanism of dots in the

2022-10-22
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The formation and production mechanism of the midpoint of the printed manuscript VII

VI. dot angle

dot angle refers to the angle between the dot arrangement line and the horizontal line

the human vision feels the most beautiful and comfortable at the 45 degree point angle, and the image performance is also the most stable and not rigid; The point angle of 0 or 90 degrees is the most uncomfortable. Even if the number of points and lines is very high, the eyes can still feel lines of dots and linear patterns, which affects the expressiveness of the picture; For a point angle of 15 degrees or 75 degrees, the human eye feels general

therefore, for monochrome eye tone printing, of course, we choose 45 degree dots

however, for multi-color and eye tone prints, the angles of the color plates must be staggered to prevent moire

based on this, the commonly used color line angles in the world are as follows:

(1) when printing in two colors, the angle of 45 degrees is used for dark color version or main color version, and 15 degrees is used for light color version or sub color version

(2) when printing in three colors, the dark version or the main color version uses 45 degrees, and the other two-color version uses 15 degrees and 75 degrees

(3) in four-color printing, 45 ° angle is used for the main color plate, 90 ° angle is used for the yellow plate, and 15 ° and 75 ° angles are used for the other two colors respectively

the reason can be analyzed from the following aspects:

(1) from the perspective of color rendering performance: among the four colors of yellow, magenta, cyan and black, yellow has the weakest visual induction, magenta and cyan take the second place, and black has the strongest induction. Therefore, China's traditional photo overtime, black version - 45 degrees; Magenta version - 15 degrees; Green low thickness version - 75 degrees; Yellow version - 90 degrees

(2) from the moire characteristics: yellow, magenta and cyan will produce obvious orange, red or green moire, and the moire produced by yellow and black is quite not obvious. Therefore, if the main color of the pattern is red, it can be set to: magenta version - 45 degrees; Black version - 15 degrees; Green version - 75 degrees; Yellow version - 90 degrees; If green is the main color, then: green version - 45 degrees; Black version - 75 degrees; Magenta version - 15 degrees; Yellow version - 90 degrees

(3) from the perspective of the original point of the eye tone original: if the original used is a copy of the printed matter, that is, the eye tone original, there are points on the original itself. When copying, color separation and addition will cause overlap and serious moire. At this time, the scanned original should be eliminated first, that is, change the scanning light hole and increase it as much as possible to reduce the image resolving force, or adjust the virtual focal length until the virtual spot on the original can't be seen clearly, or use the elimination instruction in Photoshop software to eliminate it again and again. Of course, these operation methods are effective in eliminating the spots on the original, but they have a certain impact on the color separation and quality of the original, reducing the clarity of the product. If the elimination is not complete, moire will still appear when printing. If the clarity of the product is highly required and moire is not allowed, the point angle selected for each color plate during reproduction should be staggered from the point angle of the corresponding color plate on the original. For example:

the original is: magenta version - 45 degrees; Black version - 15 degrees; Green version - 75 degrees; Yellow version - 90 degrees; When printing, it can be changed to: Yellow Version - 45 degrees; Magenta Edition - its related innovative technology will directly affect the environmental protection, durability, comfort, thermal insulation and other properties of products by 15 degrees; Black one 75 degrees; Green version a 90 degree or other point angle arrangement

VII. Prospect of additive technology

through the analysis of point four elements, the mechanism of continuously adjusting the original to copy into eye tone printed matter is clarified. This additive technology is widely used in the current printing industry. It is a traditional additive method, also known as amplitude modulation (AM). Its point spacing is equal, the size is different, the screen angle is set strictly, the intensity level of the picture is reproduced through point size, and the tone reproduction is stable. However, printing products are easy to produce moire, the picture will jump color, broken lines, printing overprint accuracy requirements and other deficiencies affect its development prospects

in the more than 100 years of the development of modern printing technology, processing technology has also unwittingly taken a big step. The emergence and application of FM processing technology has brought a breeze to the printing industry

FM (frequency modulation) refers to the same size and different spacing of points in the unit area, and reflects the tonal level of the image through the density of points. As shown in Figure 18, the picture is an irregular arrangement of very small pixels (about 10-20 microns in diameter), with dense dots, high picture density, sparse dots, and low picture density, thus reproducing the intensity level of the original. The smaller the dots are, the more high-quality tones, colors and sharpness can be reproduced. KPL mainly produces APET, PP and hips. Its imaging principle is similar to the precipitation of fine silver salt particles on the film to form images. The dots are fine, the color changes are soft, and the density is high. As long as the dots are small enough, the printed matter and the original can be quite lifelike. Of course, the higher the performance of the computer required. In particular, random and irregular points completely eliminate the generation of moire, and increase the tolerance of overprint accuracy and color number tolerance of overprint color, which can achieve the special printing effect of high fidelity that is difficult to achieve in conventional four-color overprint

figure 18

however, due to the small FM plus points, only 10-20 microns, which is equivalent to 1% - 2% points in the general 175 line am plus products, it is very easy to lose in copying, printing and printing, and the FM points are easy to expand, generally between 20% - 40%. Therefore, the printing of FM products has high requirements for printing operation, process, equipment, materials, technology and environmental temperature and humidity

of course, the development of printing technology will increasingly meet the printing requirements of FM products. For example:

(1) waterless offset printing technology greatly reduces the dot expansion rate, and can replicate finer dots and higher ink density

(2) CTP direct plate making technology and digital printing technology eliminate the processes of copying and printing, and point transfer is more direct and less deformation

(3) the application of high-quality equipment and materials can adapt to higher requirements of printing

source: printed in China

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