How to correctly select the black version in the printing plate making of the photo original with the color of the characters as the main body in paper box printing?

For the photo manuscript with the skin color of the characters as the main body, there are generally two situations in the actual production:

First, the figure photos with light on the front;
Secondly, the photo of the person's face backlighting is positive to the light. In order to make the softer transition between the solid color and the tone tone in the character's skin tone soften, to adapt to the needs of the facial tone of the character, the long tone black plate scanning can be used. The starting point of the image reproduction hierarchy curve can be extended appropriately, while enhancing the facial tone level of the character, it will reduce the inherent color of the black plate to the extreme net and transition to the middle color tone, which will make the black plate in the facial skin area dot very small, while the layer is strong and strong, and the edges are not hardened. With this method of long and short adjustment, the black plate can achieve the purpose of protecting the tone without affecting the color in paper box printing. For the picture with backlight as the central theme of the character's face because

The color position is in the shadow area, and the color is cold and gray. We should choose the black version of the skeleton and increase the dot size of the black plate accordingly, so as to compensate for the loss of printing density caused by the step down of the three primary colors, strengthen the dark tone and increase the given value of the dot, so that the dark version can enhance the steepness while reducing the middle color adjustment, and make the dark backlight photograph change.