In the printing process, continuous tone and halftone images are adjusted by the density of the dots. And by mixing CMYK four-color dots, you can show an infinite number of colors.
1. Amplitude modulation outlets
Amplitude modulation outlets are currently the most widely used outlets. Its dot density is fixed, and by adjusting the size of the dots to express the depth of color, so as to achieve the transition of tones. In printing, the use of amplitude modulation dots mainly needs to consider factors such as dot size, dot shape, dot angle, and line accuracy.
Second, the size of the outlet
The dot size is determined by the coverage of the dot, also known as the ink rate. It is customary to like to use "come" as the unit of measurement. For example, the outlets with 10% coverage are called "10% outlets", and the outlets with 20% coverage are called "20% outlets". In addition, the outlets with 0% coverage are called It is called “out of the netâ€, and the outlets with 100% coverage are called “on the groundâ€.
The tone of the printed matter is generally divided into three levels: bright tone, middle tone, and dark tone. The dot coverage of the bright tone part is about 10% to 30%; the dot coverage of the middle tone part is about 40% to 60%; the dark tone part is 70% to 90%. The net and field parts are divided separately.
Third, the shape of the dot
The shape of the dots in printing is not just a circle that everyone imagines. It is divided by the shape of the dots at 50% inking rate. It can be divided into three types: square, round, and diamond.
The square dots form a checkerboard shape with 50% coverage. Its particles are relatively sharp and have a strong ability to express levels. Suitable for the performance of lines, graphics and some hard-tuned images.
The circular dots are independent in the case of bright tone or middle tone, and only partially connected in the case of dark tone. Therefore, for the poor performance of the mining level, it is rarely used in four-color printing.
The diamond-shaped dots combine the hard tone of the square dots and the soft tone of the round dots, and the color transition is natural, which is suitable for the expression of general images and photos.
Fourth, the outlet angle
In printing plate making, the choice of dot angle plays a crucial role. Choosing the wrong dot angle will cause interference fringes.
Common dot angles are 90 degrees, 15 degrees, 45 degrees, and 75 degrees. The 45-degree dots perform best and are stable without appearing dull; the 15-degree and 75-degree angles are less stable, but the visual effects are not dull; the 90-degree angles are the most stable, but the visual effects are too dull , No beauty.
When two or more kinds of dots are put together, there will be mutual interference. When the interference is serious enough to affect the appearance of the image, the commonly known "turtle" appears.
Generally speaking, when the angle difference between the two dots is between 30 degrees and 60 degrees, the overall interference fringe is still beautiful; the second is the angle difference between the dots at 45 degrees; when the angle difference between the two dots is 15 degrees and 75 degrees At this time, the interference fringes will damage the image.
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