Correction of pictures with poor quality of the original in prepress production (2)
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(5) thick and boring manuscript
A thick and boring original with a high optical density of 0.5 or more and even more than 1.0. Due to insufficient exposure or lack of development, the dark level of the image mostly falls on the toe and the lower half of the negative characteristic curve. The main part of this kind of manuscript is dark and dark, and it is in the 2nd and 3rd grades of the new standard system of brightness. The level of brightness is small, the level of middle and dark is rich and the level is soft, and the area ratio is very large. In the middle density range, the production should be lightened to improve the reproduction to brighten the brightness and approach the standard brightness. The black and white field calibration density value should be larger, and the medium and dark tone level curve should be slightly reduced. It should be made to brighten the middle and bright tone levels including the main body to achieve better tone contrast. And visual brightness effects.
(6) Originals with different levels of intermediate adjustment
Some medium-and high-density contrast originals have fewer mid-levels and larger density differences, while higher and lower-key levels are more and more flat. For example, color films taken in backlighting should be designed to make the horizontal and dark coordination of such image subjects. A better copy reproduction effect can be obtained.
The size of the image level contrast can be adjusted for density range compression when copying. The height of the initial density can also be changed by the adjustment of the high optical density setting and the recording setting. The contrast range of the transmitted originals is very different, while the color prints are reproduced as a picture with a substantially uniform density range. This density range is much lower than that of the color original. When the color separation plate is made, the compression adjustment is inevitable.
The density of printed matter is large, which can reproduce some originals or the level of the original scene, and also make the contrast between the levels of each level open, and the stereoscopic effect is strong. In particular, it enhances the subtle contrast and enhances the sharpness of the image hierarchy. On the other hand, the color of the picture is also opened, and the deep is saturated and the shallow is clear. However, the improvement of the density of the printed ink layer is inconsistent with the increase of the dot size, and it is impossible to achieve the high density as the color transparent film. Only under the excellent conditions of paper, ink, equipment, and precision of the printing machine can the Lower dot gain and higher ink layer density. The objective technical criterion for determining this quality index is to use a color reflection densitometer to measure the printed solid density and 75% dot print density of each printing ink layer, and calculate the printed K value. When the value is higher (yellow version 0.3~0.4, magenta version and green version 0.4~0.55, black version 0.5~0.6), their respective solid density is higher, and the overprinting efficiency of each color ink layer is close to 90%. The tone of the print is better. In order to save ink, some people advocate reducing the density of the printed ink layer to reduce the dot gain, but this will reduce the leveling phenomenon of the image dark layer. The overall tone contrast is not the highest, and the best printing order is not achieved. Reconcile the level.
Since the printing process tone is a nonlinear transmission, compensation adjustment should be made before printing. In order to be suitable for the printing process, it is necessary to adjust the three dot jump areas of the printing, that is, 3%, 50%, and 80% dot areas. Because 3% of small points are easy to lose, it will affect the color level of the highlight area. The 50% dot area is easy to increase, which will affect the middle tone and the change of the skin color of the special characters. 80% of the dot area is easy to level, which will affect the dark level, especially the level of the main color of the dark tone and the depth of the primary color, making it difficult to print both. Therefore, the important color and important parts of the original should be adjusted to avoid the three dot jump areas.
4. Original document definition problem and processing method
(1) The solidity of the image hierarchy
First, there must be a solidity (ie, sharpness) of the boundary of the original document as the basis. In the whole process of copy reproduction, the transition width of the image hierarchy boundary is to be gradually widened, especially to enlarge the copy. The level of boundary solidity cannot be restored. The sharpness of the borders of the prints is only apparently highlighted by the separation of the separations.
(2) The clarity of the contrast between the two adjacent levels of the image
If the density of adjacent layers is large, the visual experience is clear. It can be emphasized by the contrast of the hierarchical boundary in the color separation, which will cause the illusion of improvement, and the contrast of the subtle level can be substantially strengthened.
(3) Resolution of the original or printed image hierarchy
The so-called texture. The print is based on the subtle resolution of the original image, but is subject to the influence of the resolution, magnification, thickness of the wire and the four-color version of the plated optics. Through the plate-making process, the subtlety of the original level cannot be restored.