Several ways to adjust the contrast of picture before book printing
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When compressing the original gradation contrast, in general, the following methods are often used to compress certain parts.
1 Under normal circumstances, the normal manuscript, the contrast is appropriate, should make the low-key level to be flattened, especially when it is necessary to emphasize the middle tone and the brightness level.
2 The original is boring, and the tone is flat. If the emphasis is on the dark tone and the middle tone level, the middle tone level will be flattened accordingly.
3 The contrast of the original is boring, and the whole painting-face-low-adjustment-face-product-large is supposed to open the low-key level, but the middle-tone level is flat.
4 The intermediate adjustment level is relatively flat, the contrast is small, and the brightness adjustment level can be compressed, so that the middle adjustment level contrast is larger.
5 Original contrast is basically suitable for printing and copying. It is a photo with a middle tone. The dark tone - face - product - is small, and the dark tone level can be compressed to emphasize the middle tone level.
6 often encounter color photos, these originals are thin, the contrast is small, for these originals, you can compress the light and dark levels, making the contrast of the intermediate level is larger.
7 encountered the original light level flat, the contrast is small, you can open the bright level, but the middle level is flat.
The contrast of the natural color positive film of the transmission manuscript is relatively large, about 3.0, usually the compression contrast is needed to achieve the copying requirements of the printed matter; while the contrast of the manuscript of the reflective manuscript is small, the original is boring, according to different original features. Make a bright copy. For example, the copying point of a portrait is the color of the character, and the two colors of y and m are the key; the focus of the landscape is the natural scenery, and the two colors of y and c are the main points. Flexibly use the hierarchical travel button, adjust the reasonable level curve, correct the deficiencies of the original, maintain the main part, and correspondingly lose the secondary part, boldly choose, try to replicate the better effect. However, if the adjustment of the level curve is unreasonable, it may cause the image to be reversed first, the level is unclear, and the hue is inaccurate.
The color reproduction of printed matter mainly has the disadvantages of insufficient basic color, and the opposite color is excessive. To copy high-quality printed products, it is necessary to deepen the basic color without losing the level. The basic color should reach 100%, the moderate basic color should be full, the light basic color should be appropriate, and the bright basic color can not be lost.
The opposite color should be appropriate. Since the purity of the ink on the market is not bright enough, the hue and transparency are poor, and the whiteness of the paper is poor and the smoothness is poor. Therefore, when using the color, it should be noted that the brighter color complementary color (the opposite color) is smaller and thicker. The complementary color of the color should be used. The brightest face-face-product color complementary color can be used, so it plays the role of color change and contrasting layer. When used properly, the basic color can be made more vivid, thick and rich in color.
The color reproduction of the printed matter is actually an additive color reproduction of the primary colors y, m, and c of the color material with the reduced color light as the primary color. The three primary colors of y, m, and c color are the basic three primary colors of all colorful colors. Black - version - can not afford any color change, black - version - the role is only to stabilize the gray balance, play a skeleton role in the color picture, make the dark tone darker, emphasize low-key levels and contours, enhance the picture The thickness and three-dimensionality. The three primary colors of y, m, and c pigments transition to the black field, that is, y+m+c=approximate black. A part of the formed neutral color (three primary colors) is removed from the three primary colors of y, m, c and replaced with black ink. This is the method of background color removal (UCR) for electric extensions and Apple computers. There are many reasons for the removal of the background color: 1 Improve the suitability of printing, generally used in the dark adjustment, in the dark adjustment area, if printing with three primary colors, the dot-face-product is often very high, in high-speed multi-color printing It is easy to produce problems such as excessive thickness of the ink layer and paste-----.