Some friends always feel that the contrast, lack of sharpness, and color cast may occur when the image is scanned, which may be caused by poorly set black and white fields in the scan. In general, the so-called “highlight point†should be: The brightest point in the image that begins to appear at the bright tone level, but it is not the “brightest point†that is the brightest part of the image. "Dark tone point" is generally the end point of the image tone level, but it is not the darkest point.
Coated paper printing requires bright spots that cannot be screened (ie, the four-color dots are all 0). Therefore, be careful when selecting areas with high light. The brightest four-color settings are: C5, M3, Y3, and K0. Or can be brighter: C4, M2, Y2, K0, if the original is too bright or too dark, the set value can be changed, but it should ensure that the value of the brightest point is basically the above value, no net phenomenon can occur . The setting of the black field should pay attention to the total amount of ordinary offset ink in the range of 320-360. Too thin will cause the printed image to be unsaturated in color and the color is not bright, and the dark tone part C version must be larger than the M version and the Y version. K version can not be less than 80, otherwise there will be color cast, dark tone gray phenomenon, the general set value is: C90, M85, Y85, K80, if the printing factory conditions are good, the printing product requirements are high, you can do: C95 , M90, Y90, K85, such a good contrast of print, rich levels.
The printing of newspapers is web printing, which is fast and the ink drying time is short. Therefore, the ink cannot be too thick in the process of copying, and the total dot area rate of four-color printing should be limited. At the same time, a large proportion of gray components should be used instead. . According to the characteristics of newspapers, the minimum dot area rate that can be completely transmitted to newsprint is between 6% and 8%. When selecting the highlight point, the area ratio of the highlight spot of the image should begin to appear brighter than this range, otherwise the transmission of the highlight spot will be incomplete or completely lost, so that the original tone of the image will be changed into a white Extreme light of paper. The dark spots can not be like ordinary offset printing, the total amount of ink can only reach 270-300, so can be set as: C60 ~ 65, M50 ~ 55, Y50 ~ 55, K90 ~ 95