The correction of pictures with poor manuscript quality in prepress production (2)

High-light density of more than 0.5, even more than 1.0 thick stuffy manuscript. Due to multiple shooting exposures or insufficient development, most of the image darkness levels fall on the toes of the negative image characteristic curve and the lower half of the straight line. The main body of this type of manuscript is darker and darker, and it is located in Levels 2 and 3 of the Shinsei Shinbiao System. There are few bright tone levels, and the dark tone levels are rich and the level difference is soft, and the area ratio is large. In the mid-range density range, the reproduction should be reduced by increasing the lightness in order to brighten the brightness and approach the standard lightness. The black and white field calibration density value should be larger, the level curve of medium and dark tone should be lightened slightly, and the medium brightness level including the main tone should be reproduced brightly so as to achieve better tone contrast. And visual brightness effect.

(6) Different manuscripts distributed at the midtone level

Some manuscripts with medium-to-dense contrasts have fewer intermediate tone levels, a greater density difference, and high and low tone levels, such as color films shot against the light, should be designed to adjust the level of darkness of this type of image subject. Good copy reproduction effect can be achieved.
The level of contrast in the image can be used as a density range compression adjustment when copying. The height of the initial density can also be changed by setting the high optical density and adjusting the recording settings. The contrast range of transmission originals is very different, and color prints have to be reproduced as a screen with a substantially uniform density range. This density range is mostly lower than that of color originals. When color separation is used for plate making, it must be compressed and adjusted.

The range of print density is large, which can reproduce the levels of some originals or original scenes, and also make the contrast between levels more openable. The sense of three-dimensionality is also strong. In particular, the subtle contrasts can be enhanced and the clarity of the image hierarchy can also be enhanced. On the Other hand, the color of the picture is also pulled open. The deeper ones are saturated and the shallower ones are brighter. However, the increase in the density of the printing ink layer is inconsistent with the increase in the number of dots, and it is impossible to achieve such a high density as a color transparency sheet. Only when the paper, ink, and equipment have the appropriate characteristics and the precision of the printing press can the quality be improved. Lower dot gain and higher ink layer density. The objective technical standard for determining this quality index is to use a color reflection densitometer to measure the printed solid density and 75% dot printing density of each printing ink layer, and calculate the printing K value. When this value is higher (0.3 to 0.4 for the yellow version, 0.4 to 0.55 for the magenta and cyan plates, and 0.5 to 0.6 for the black plates), the density of each of them is high, and the superimposition efficiency of each ink layer approaches 90%. The tone of the print is also better. In order to save ink, some people advocate reducing the density of the printing ink layer to reduce the dot gain, but this will reduce the leveling phenomenon of the dark tone layer of the image. The overall tone contrast is not the highest and the best printing level is not achieved. Level reproduction.

Due to the non-linear transmission of the printing process tone, compensation adjustments should be made before printing. In order to suit the printing process, it is necessary to adjust the printing area of ​​the three outlets, ie, 3%, 50%, and 80% outlet areas. Because 3% of small dots are easy to lose, it will affect the color gradation of the highlight area, and 50% of the dot area will easily increase, which will affect the midtones and changes in the color of the special characters. The 80% dot area is easy to merge, affecting the dark tone level, and in particular the dark color tone of the main color and the depth of the primary color, so that it is difficult to balance both the printing. Therefore, important colors and important parts of the manuscript should be adjusted so as to avoid these three dot jump zones.

IV. Manuscript definition problems and processing methods

(1) The solidity of the image hierarchy

First, it is necessary to base the factual (ie, sharpness) of the boundaries of the manuscript hierarchy. In the whole process of copying and reproduction, the transition width of the image level boundary is gradually widened, especially enlarged copying. The level boundary reality cannot be restored. The sharpness of the borders of the print hierarchy just seems to be emphasized by the separation of the colors.

(2) The clarity of contrast changes in two adjacent levels of the image

If the density of adjacent levels is very different, the visual experience is clear. It is possible to emphasize the contrast of the level boundaries during the color separation and to create an illusion of improvement. Subtle levels of contrast can be substantially enhanced.

(3) The resolution of the original or print screen hierarchy

The so-called texture. Prints are based on the fine-grained resolution of the original image, but are compromised by the resolution of the plate-making optics, the magnification, the thickness of the cable, and the impact of the four-color version. After the plate printing process, the fineness of the original layer cannot be restored.