In the field of books and packaging printing, color printing has become the mainstream of printing, and the quality of printed matter is also increasing. However, due to the influence of subjective and objective factors, there are not many high-quality products, which can not be compared with foreign high-quality products. We know that the quality of color prints is subject to many factors in the reproduction process, such as the tone level of the color original image, dot expansion value, color balance, etc., and the quality of the pre-press image production directly determines the quality of the color printing, although some deficiencies can be partially corrected in plate printing, but basically there is nothing to be done to print out the fine. Therefore, when making images before press, if you find that the quality of the original is insufficient, you should find ways to correct it. Below, a brief introduction to some processing techniques and methods.
(1) Color bias of the original manuscript
Generally divided into overall color bias, low profile color bias, high profile color bias and high profile color bias of different colors (that is, cross color bias). Therefore, the correction should be considered as a whole, can not see a color immediately deal with a color, otherwise it will cause other color.
(2) Manuscript density
The difference between the maximum and minimum density in the manuscript (that is, the contrast), the maximum density value that can be reached by the general print is 1.8, the maximum density of the printed paper image is 1.7, and the density of the black ink in the manuscript is 1.8. In general, all the density of the manuscript can only be reproduced in the range of 0 to 1.8 on white paper, so for the manuscript, there is a density range suitable for plate printing. When the density range of the original manuscript is too large, the sensitivity of the scanner and the extension to the part beyond the density range is reduced, so the level of the color separation plate is flat. According to practice, the original manuscript is 0.3~2.1, that is, the most appropriate when the contrast is 1.8. Color negative original density difference is controlled within 2.4; If the contrast of the original is less than 2.5, the effect is also ideal when copying reasonable compression, if the contrast of the original is greater than 2.5, even if the step compression is carried out when copying, the level will be lost too much, and the effect is poor.
(3) The original level
There are three main indicators to measure the quality of replicas: level, color and clarity, and the level is the most important. The level of the normal manuscript should have the characteristics of the picture is not bright and dark, high, medium and low profile, more density changes, rich levels and so on.
