(1) Screen angle: In the four-color printing, the amplitude of the AM screens is regularly arranged. Under the overprinting of several colors, the printed matter may produce markings that affect the aesthetics of the image, ie, the moiré stripes in the printing, commonly known as the moiré pattern. In order to reduce the effect of moiré on the printed image, the screening angle must follow the following rules:
The angle difference between the cyan, magenta, and black plates is 30° to 60°, and the difference between the yellow plate and other plates is 15°. The main color version has a screening angle of 45°. Two commonly used screening angles are recommended: 1 Yellow Edition 90°, Magenta 75°, Cyan 15°, Black Edition 45°; 2 Yellow Edition 90°, Magenta 45°, Cyan 75° (or 15°) , Black Edition 15 ° (or 75 °). Sometimes the angle can be appropriately arranged according to the level and hue that the print needs to express. For example, the color plate corresponding to the main hue can be highlighted with 45°.
When using a print as a manuscript, the screen angle selected for each color version should be offset from the corresponding screen angle on the original. For example, the original version is 90° in yellow, magenta is 75°, cyan is 15°, and black is 45°. Yellow 45°, magenta 30°, cyan 60°, and black 90°. When the spot color is screened, according to the actual situation, the appropriate screening angle is determined according to the above-mentioned law.
Here it is necessary to talk about the angle of screen printing commonly used in newspaper printing. Since newspapers use more “grey component substitution†(background color removal), the black version is a long tone. Therefore, the angles of the screens of the four-color newspapers are set to be 45° for black, 90° for yellow, 15° or 75° for magenta and cyan. The screen angle of the image should be 45° when printed in monochrome.
(2) Screen number: The number of common screen lines is 80lpi, 100lpi, 120lpi, 133lpi, 150lpi, 175lpi, 200lpi. In practical applications, the appropriate number of screen lines is generally selected according to the performance of the paper and the performance of the printing equipment. The printing of rough surface paper, such as newsprint used in newspaper printing, is generally 80-133 lpi; offset paper is generally used. With 120-150dpi, copperplate and advanced calendered paper can choose 175lpi or 200lpi or even higher. It should be noted that do not go into the misunderstanding of the high-line cable. The high-line cable has higher technical requirements for printing plates, paper and printing machines, and operation. If they are used improperly, high-profile loss, dark-sounding convergence, and flatness may occur. Network jitter and other phenomena, in addition, if the quality of the original is poor, with high network cable will highlight its defects. Under normal circumstances, the resolution of the image should be 1.5 to 2 times the number of screens, and it is recommended to use 2 times.
(3) Characteristics of the film: For the most commonly used positive-working plates, the film is positive and the film surface should be downward. (This film is called "anti-yang"). For the negative plate type, a negative image is produced with the film facing downward. The field density of the image-setter output film should be between 4.0 and 4.2, and the minimum output density should not be less than 3.5, otherwise it will affect the quality of the printing plate. Factors that affect the film density are: film type, exposure intensity, development time, development temperature, etc.
The angle difference between the cyan, magenta, and black plates is 30° to 60°, and the difference between the yellow plate and other plates is 15°. The main color version has a screening angle of 45°. Two commonly used screening angles are recommended: 1 Yellow Edition 90°, Magenta 75°, Cyan 15°, Black Edition 45°; 2 Yellow Edition 90°, Magenta 45°, Cyan 75° (or 15°) , Black Edition 15 ° (or 75 °). Sometimes the angle can be appropriately arranged according to the level and hue that the print needs to express. For example, the color plate corresponding to the main hue can be highlighted with 45°.
When using a print as a manuscript, the screen angle selected for each color version should be offset from the corresponding screen angle on the original. For example, the original version is 90° in yellow, magenta is 75°, cyan is 15°, and black is 45°. Yellow 45°, magenta 30°, cyan 60°, and black 90°. When the spot color is screened, according to the actual situation, the appropriate screening angle is determined according to the above-mentioned law.
Here it is necessary to talk about the angle of screen printing commonly used in newspaper printing. Since newspapers use more “grey component substitution†(background color removal), the black version is a long tone. Therefore, the angles of the screens of the four-color newspapers are set to be 45° for black, 90° for yellow, 15° or 75° for magenta and cyan. The screen angle of the image should be 45° when printed in monochrome.
(2) Screen number: The number of common screen lines is 80lpi, 100lpi, 120lpi, 133lpi, 150lpi, 175lpi, 200lpi. In practical applications, the appropriate number of screen lines is generally selected according to the performance of the paper and the performance of the printing equipment. The printing of rough surface paper, such as newsprint used in newspaper printing, is generally 80-133 lpi; offset paper is generally used. With 120-150dpi, copperplate and advanced calendered paper can choose 175lpi or 200lpi or even higher. It should be noted that do not go into the misunderstanding of the high-line cable. The high-line cable has higher technical requirements for printing plates, paper and printing machines, and operation. If they are used improperly, high-profile loss, dark-sounding convergence, and flatness may occur. Network jitter and other phenomena, in addition, if the quality of the original is poor, with high network cable will highlight its defects. Under normal circumstances, the resolution of the image should be 1.5 to 2 times the number of screens, and it is recommended to use 2 times.
(3) Characteristics of the film: For the most commonly used positive-working plates, the film is positive and the film surface should be downward. (This film is called "anti-yang"). For the negative plate type, a negative image is produced with the film facing downward. The field density of the image-setter output film should be between 4.0 and 4.2, and the minimum output density should not be less than 3.5, otherwise it will affect the quality of the printing plate. Factors that affect the film density are: film type, exposure intensity, development time, development temperature, etc.
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