Hottest printing image information processing 3

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Printing image information processing

III. photographing process of monochrome continuous tone image manuscript

the photographing process of monochrome continuous tone image manuscript is basically the same as that of line manuscript, except that when photographing, the screen should be placed in front of the photosensitive sheet, as shown in Figure 3-20. After passing through the lens, the light beams with different brightness reflected or transmitted from the original meet the screen before reaching the photographic plate. Because the hole has the function of redistributing the luminous flux, the light beams passing through the hole are divided into small parts of the luminous flux corresponding to the original, forming points on the photographic plate. The bright parts on the original form large points on the negative film, and the dark parts on the original, Form dots on negative film

in Figure 3-20, the continuous adjustment manuscript of

monochrome is shot. Generally, the photographic film is used, and the contact screen is used to shoot at a 45 ° point angle. The process flow is as follows:

install the manuscript → install the photographic film and screen → add aiming → exposure → development → fixing → water washing

during exposure, the main exposure and auxiliary exposure shall be carried out according to the characteristics of the manuscript. Auxiliary exposure includes flash exposure and highlight exposure

the main exposure is to shoot the original through the screen. Through the main exposure, the basic situation of hierarchical reproduction is determined. Flash exposure: the light emitted by the light source does not pass through the original but passes through the screen. The purpose is to make the dark part of the original fill small dots on the negative film, extend the middle or cover the dust plug to adjust to the dark tone. The high light exposure is carried out after the main exposure and flash exposure are completed. The screen is removed during exposure to open the level of the light adjustment part and improve the contrast of the high light part

the negative image and negative film taken shall meet the following quality requirements: the layout shall be clear without yellowing and dirty spots, the image warp film shall be free of scratches, the spots shall be bright and clean, and the density shall meet the printing requirements

negative image plus negative film can be reproduced or copied into positive image plus negative film according to the needs of plate making. Negative or positive film with dots is called "plus" film relative to continuous adjustment of originals or films. The addition film can also be taken with wet film or gelatin dry film. However, due to the complex process and difficult quality control, it can only be used in special cases

in the process of adding, there are terms to express the reproduction of tone, such as deep, flat, light, cut, etc

depth: it means that the area of image points is too large

flat: it means that the area of the bright part of the image is too large, and the area of the dark part is too small, and the level is not obvious

light: the area of image points is too small

sharp: it means that the dot area of the bright part of the image is too small, the dot area of the dark part is too large, and the contrast between light and shade is too large

IV. photographic process of color image originals

color image originals can be photographed by indirect color separation addition and direct color separation addition to obtain color separation plus negative or positive negative

(I) indirect color separation and addition, Therefore, it is also called "two-step process method", and the process is shown in Figure 3-21.

figure 3-21 indirect color separation and addition process Direct color separation and addition

direct color separation and addition process is to install the color filter and the contact screen on the plate making camera at the same time, and record the step call point on the original directly on the color separation film, so that the two processes of color separation and addition can be completed at one time, so it is also "direct hanging". The process is shown in Figure 3-22

Fig. 3-22 we found that the direct color separation and addition process when heating wood flour

the direct color separation and addition process needs to make a mask, compress the contrast of the original, correct the color difference, and use a strong light source, a contact screen with correct layers and a panchromatic film with high photosensitivity. At present, in China, it is mainly used for color separation and addition of Chinese paintings and originals similar to the style of Chinese paintings

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