Pay attention to dot increase in the hottest color

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Attention should be paid to the increase in color plate making

the technical indicators of color image reproduction technology, such as tone level, color change, relative contrast value (k value), are all completed by point reproduction. Dot gain will cause the decrease of clarity and the loss of fine levels, the change of color, as well as the problems of contrast, ink tone, ink density and ink overprint. The size of dots and the position between them determine the tone and quality of printing. Therefore, in the process of color image reproduction, we should effectively control the point increase

the point increase we see on the sample or print is the sum of "optical point increase" and "mechanical point increase". "Optical point increase" is a visual phenomenon formed by the light absorption characteristics of ink and the light scattering of substrate. When the light shines on the blank area, the light diffuses, and part of the light near the point is suppressed, which is considered to be absorbed because it cannot be reflected back to the observer's eyes. The dots appear darker and larger than the actual density and size, and it seems that the dots have increased. "Mechanical dot increase" refers to the physical increase of dots actually generated during color separation, film turning, copying, plate printing, proofing and printing. The prepress factors that make up the dot increase include dot shape, line thickness, plate making process and environmental conditions, exposure, washing and operation methods, equipment performance, etc

diamond shaped points are easier to produce point enlargement than other shape points. Because the perimeter of diamond shaped points is relatively long, diamond shaped points are suitable for images with a large number of obvious intermediate fine levels. In order to reduce the point increase, if it is due to the reason of the gasket, most printing manufacturers like to use circular points, because the circular makes the enclosed area reach the maximum and the perimeter is the shortest

the number of EYELINES is selected according to the clarity and fineness of the original. The higher the number of EYELINES, the better the fine level effect copied, the better the texture and color of the image, but the higher the dot increase during printing. Generally speaking, a lower number of EYELINES produces less point increase. In printing, it is difficult to control the number of high mesh lines. The number of eyelets used depends on the type of product printed. The higher the grade of the product, the higher the number of eyelets

random addition is also called frequency modulation addition. It generates tone illusion by changing the number (frequency) of small size points of high-performance elastopan and cellasto materials in a small area of medium and micro sole. Its advantage is that there is no intuitive point graphics, no moire, no tone jump, without losing quality, it can adjust the resolving power and gray level at the same time, and there is no blocking phenomenon. The point increase of random addition is about twice that of ordinary addition. Generally, the common visible addition increases by about 20%, while the random addition is 25% - 40%

the most important thing for photographic processing is to select the correct exposure, and also to consider compensating for the dot increase generated during printing. The dots on the film image will increase during printing, which is caused by the dot edge effect on the negative image. Point edge refers to the part with fine density on the outer edge of each point on the screen, and points with large edges are commonly known as "virtual points". In early May 2016, the old craft plate making will have false points. When the false point is serious, mainly check the developer and the development process, especially the development temperature. Virtual points can also be changed into real points by copying

in plate making, exposure is very critical. Slight changes will affect the size of points, light source, lamp distance, voltage, vacuum absorption time, film flatness, thickness, production method, materials and equipment, environment, and operator quality will affect the reproduction accuracy of points, which should be strictly controlled

in the process of plate making, it is required to have clear points, accurate angles, no ghosting, and control the increase value, K value and field density of 50% points. Dot clarity means to control the density and smoothness of printing inking dots. To achieve: the high-profile small points should be complete, the middle adjustment points should be really bright and clean, the large points should be bright and clean without paste, the ink layer conjunctiva is firm, the density meets the requirements, the angle is correct, and the points do not have excessive enlargement, ghosting, etc. The level of point definition is directly related to the image's tone level, definition, quality, three-dimensional sense, perspective sense, etc. The law of point increase is to expand outward from the edge of the point (points with an area of more than 60% expand to the inner circle). Since the point increase value is proportional to the point edge length, the point with 50% area increases the most. It is required that the increment value of 50% points is 8% - 20% for fine products and 10% - 25% for general products. When the basic color of the sample or printed image is not full, the middle is leveled gray, and there is a lack of stereoscopic feeling, it can be seen that the point increases beyond the standard, and it is necessary to remake the plate

The value of

k is the ratio of the difference between the integral density of the field and the eye tone to the field density. It is a measure to measure whether the field printing ink volume and the picture contrast meet the requirements. At the same time, the increase degree of the point can also be judged by the value of K. When the K value is large, the picture appears gray and light, losing the effect of thick tone and contrast. K value is small, the whole tone of the picture is darker, and the middle is flat and gray. During plate making, the relative contrast value of fine print: Yellow 0..35, magenta and green 0..45, black 0..50; The relative contrast value of general printed matter: Yellow 0..30, magenta and green 0..40, black 0..45

at the same time, in the process of plate making, we should also control the field density of various colors. Achieve: the field density of fine printing is yellow 0..15, magenta 1..55, cyan 1..60, black 1..80, and the field density of general printing crystal: Yellow 0..10, cyan 1..45, cyan 1..55, black 1..60

source; Printing world

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