Correction of pictures with poor quality of the ho

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Correction of pictures with poor original quality in prepress production (2)

5) thick and dull originals with a high optical density of more than 0.5, or even more than 1.0. Most of them are caused by insufficient shooting exposure or development, so that most of the image's dark tone levels fall on the toes of the image characteristic curve and the lower half of the straight line when it is more negative. The main part of this kind of manuscript is dark and deep, which is at level 2 and 3 of the new lightness standard system. There are few levels of lightness, rich levels of medium and dark tones, and the level difference is flat and soft, and the area ratio is large. The main tone also falls within the range of middle note density. When making, it is necessary to reduce the lightness and improve the copy, so as to improve the lightness and approach the standard lightness. The calibration density value of the black-and-white field should be larger, and the level curve of the medium and dark tones should be slightly shallower, so that the medium and bright tone levels, including the main tone, should be reproduced brightly, so as to achieve better tone contrast and visual brightness effect

(6) originals with different intermediate tone levels

for some originals with medium and high density contrast, the middle note level is less, the density level difference is larger, and the high and low tone level is more and gentle, such as the color film taken in backlight. When making, we should find a way to make the level of the main tone of this kind of image coordinate, which can achieve a better reproduction effect

the size of the image hierarchy contrast, which can be compressed and adjusted for density range during copying. The initial density can also be changed by adjusting the highlight density setting and recording setting. The contrast range of the transmitted originals is very different, but the color printed matter has to be reproduced as a picture with basically the same density range, which is mostly lower than that of the color originals. During color separation and plate making, it is necessary to compress and adjust

the density range of printed matter is large, which can not only reproduce some layers of the original manuscript or the original scenery, but also make the contrast between the layers at all levels more open, and the three-dimensional sense is strong. In particular, it can enhance the fine level contrast and enhance the clarity of the image level. On the other hand, it also makes the color of the picture open the level. The deep is thick and saturated, and the shallow is bright. However, the increase of printing ink layer density is in contradiction with point increase, and it is impossible to achieve the high density of color transparent film. Only under the excellent conditions of paper, ink, equipment and printing machine precision, can there be low point increase value and high ink layer density. The objective technical standard to determine this quality index is to use a color reflection densimeter to measure the printing field density and 75% point printing density of each printing ink layer, and calculate its printing K value. When this value is high (yellow version 0.3~0.4, magenta version and cyan version 0.4~0.55 processing process, black version 0.5~0.6), their respective field density is high, and the overprint efficiency of each color ink layer is close to 90%, the printing tone is also better. In order to save ink, some people advocate reducing the density of printing ink layer to reduce the point increase, but this will reduce the merging phenomenon of image dark end layer. The overall tone contrast is not the highest, nor can it achieve the best reproduction of printing tone level

because the printing process gradient is nonlinear transmission, compensation adjustment should be made before printing. In order to adapt to the printing process, the three dot jump areas of printing must be adjusted, that is, 3%, 50% and 80% dot areas. Because 3% dots are easy to lose, which will affect the color level of the highlight area, and 50% dots are easy to increase, which will affect the middle tone, especially the change of the skin color of the character. 80% of the dot area is easy to be merged, which will affect the dark tone level, especially the merging of the main color of the dark tone skin color and the deep primary color, making it difficult for printing to give consideration to both. Therefore, the important colors and parts of the original should be adjusted to avoid these three point jumping areas

IV The clarity of the original and its processing methods

(1) the reality of the image hierarchical contour

first of all, the real 7 plastic granulator industry with the hierarchical boundary of the original should constantly improve its technical level 4 sampling degree (i.e. sharpness) as the basis. In the whole process of reproduction, the transition width of the image level boundary should be gradually widened, especially enlarged reproduction. The level boundary realness can no longer be restored. The clarity of the printed matter's hierarchical boundaries only seems to be emphasized by color separation reproduction

(2) the clarity of the contrast change of light and shade between two adjacent layers of the image

if the density difference between adjacent layers is large, the visual experience is clear. The contrast of the boundary of the layers can be emphasized in the color separation, which will cause the illusion of improvement, and the contrast of the subtle layers can be substantially strengthened

(3) the resolution of the original or printed picture level

is the so-called texture. Printed matter is based on the fine-grained resolution of the original image, but it is damaged by the influence of the resolution, magnification, line thickness and four-color plate nesting of the plate optics. After the process of plate making and printing, the fineness of the original level cannot be restored

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