Analysis of the hottest dot shape I

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Point shape analysis (I)

points can have different shapes. Point shape refers to the geometry of a single point, that is, the edge shape of a point. In traditional point technology, the shape of the point is determined by the corresponding screen structure. In addition to their own performance characteristics, points with different shapes also have different change rules in the process of image replication, which will produce different replication results and affect the quality requirements of replication results

points with different shapes have different image gradient transmission characteristics. In the actual plate making and printing process, the midpoint has a trend of mechanical expansion. Experiments show that this trend increases with the increase of the perimeter (or the sum of the perimeter). The sensitivity of point area ratio to perimeter changes is in direct proportion to its perimeter. Points with a larger perimeter (sum of girths) are easier to expand, and the distortion that may occur in graphic reproduction is also greater

the point shape is different, the area ratio of adjacent points is different, the number of overlapping (when the point is overlapped, it is the time of its perimeter and maximum, so the characteristics of point overlapping are often used to describe the properties of different points) is also different, and the situation of image tone transmission is different

The overlapping of

points will cause the jump of density

when choosing which shape to add to the image, the point enlarger is often the primary consideration. The different change trends of points with different shapes lead to different point selection of different products

the point shapes used in traditional addition methods include square, round, diamond (diamond), oval, double point, etc; In modern digital addition technology, more points can be selected. The following is a description of common point shapes and their characteristics

1. Square dot. When square dots are selected to copy the image, the ink and white are just alternating at 50% of the dots to form a checkerboard shape. It is easy to judge the relative percentage of square dots according to the dot spacing, which is more sensitive to the transmission of the original level. Figure 1 shows 50% square points arranged at a 90 degree angle

Figure 1 the final formation of 50% square dot shape is closely related to plate making and printing process. The square point can really show its shape only at the percentage of 50% points. When it is more than 50% or less, due to the influence of Optics and chemistry in the process of point formation, it will deform at its corners, resulting in a circle in the middle of the square or even a circle. In printing, the point area will expand due to the influence of pressure and ink viscosity. Compared with the points of other shapes, the area ratio of square points is the highest. The reason for this phenomenon is that after the area ratio of square points reaches 50%, the points are connected with the four corners of the points, and the corner connecting part is prone to ink blockage and adhesion during printing, resulting in the expansion of the points

the above seems to be the shortcomings of square points, as if there is no need for square points. In fact, it is not. In some cases, such as those where the requirements for the middle tone are not particularly strict, the selection of square dots can show a more distinctive level

2. However, it is generally bearish on the future market. Among the points of the same area, the circumference of the circular point is the shortest. When circular dots are used, the highlights and intermediate adjustment points in the picture are not connected to each other, and they can only contact each other at the dark point. Therefore, the middle of the picture steadily advances into the international market, and the increase value of the points below the tone is very small, which can better retain the intermediate level

compared with other shaped points, the main problem is that the expansion coefficient of circular points is small. Under normal circumstances, circular points are connected around 70% area ratio. Once the circular point is connected with the circular point, its expansion coefficient will be very high, which will lead to the accumulation of ink around the dark areas due to the excessive amount of ink, and eventually make the dark parts of the image lose their due level

through the above description, we will find that circular dots are limited in use due to their poor ability to express the level of dark tones. Under normal circumstances, printing plants often avoid using circular dots, especially when printing with offset paper. However, if the original image to be copied has more bright tones and less dark tones, it is quite advantageous to use circular dots to show the regional levels of high and middle note

below we give the deformation characteristic curves of square points and circular points:

pure square points overlap at 50% and pure circular points overlap at about 78%. It can be seen that when the points are not angled, the point expansion trend of square points is higher than that of circular points

statement: produce medium and low-end products

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