In the field of books and packaging and printing, color printing has become the mainstream of printing, and the quality of printed materials is also increasing. However, due to subjective and objective factors, there are not many quality grades, and it is still not comparable to foreign quality products. We know that the quality of color prints is subject to many factors such as the tone level of the color original image, the dot gain value, and the color balance. Among them, the quality of the prepress image is directly determined. The quality, although some corrections can be made in the printing and printing, but there is basically no way to print the boutique. Therefore, when making an image before printing, if the quality of the original is found to be insufficient, you should try to correct it. Below, we briefly introduce some processing techniques and methods.
(1) Original density
The difference between the maximum and minimum density in the original (ie contrast), the maximum density of prints available today is 1.8, the maximum print image is 1.7, and the black ink density of the finished original is 1.8. In general, all densities of the original can only be reproduced in the range of 0 to 1.8 on white paper, and therefore, for the original, there is a density range suitable for stencil printing. When the density range of the original is too large, the sensitivity of the scanner and the electric extension to the portion exceeding the density range is lowered, so the color separation plate is flat. According to practice, the original is 0.3 to 2.1, which is most suitable when the contrast is 1.8. The color negative document density difference is controlled within 2.4; if the original contrast is less than 2.5, reasonable compression is performed when copying, and the effect is also ideal. If the original contrast is greater than 2.5, even if the tone is compressed during copying, the layer will be lost too much. Poor.
(2) Original color cast
Generally, the overall color cast, low-key color cast, high-tone color cast, and high-low key are different colors (ie, cross color cast). Therefore, when considering the whole, we must look at the overall consideration. If we can't see a color cast, we will deal with one color immediately, otherwise it will cause other color casts.
(3) Original level
The quality of the replicas is mainly composed of three indicators: level, color and clarity, and the level is the most important. The level of the normal manuscript should be such that the picture is not bright and dark, high, medium and low-key, and the density changes are many, and the tone is rich.
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