The second problem is overprinting
When there are two colors adjoining on the page, for example: a blue circle under a yellow background, a white round hole must be dug on a yellow background under the blue circle, otherwise the blue circle presses on the yellow background. It will turn into a green circle, which is not what we want to achieve, but in the printing process, the paper on the printing press is stretched, and there will be a slight shift, and it is also difficult for the printing machine to always maintain a good position. This makes it impossible to print the blue circle on the white hole, resulting in a white gap between the circle and the background. Overprinting is the solution to this problem.
Overprinting can be used to create a transition between two colors, filling the seams that are not allowed to appear. When there are two colors on the paper, the deeper color determines the light-colored border. So there are two common overprinting methods. Dilation is used to superimpose light-colored objects on dark backgrounds; contraction is used to superimpose dark objects on light-colored backgrounds. It seems that dark colors always determine the boundaries of objects. So both methods use superficial color for superimposition while the dark part remains unchanged.
In DTP design and production, computer software such as FreeHand and Illustrator draw a graphic, its internal color and border color can be defined separately. Using this feature, you can complete the superimposition of graphics. The specific method is to set the border of the graphic as overprint, and the color is the darkest color in the graphic and background colors. For example, when superimposing, the principle of light color and dark color should be observed so that the shape of the figure does not change significantly. White--yellow--cyan--green--magenta--red--blue--black Some black celebrity inscriptions or logos can be directly defined as imprints. Comrade Deng Xiaoping's name for my school title: higher education press, we use directly defined as imprinting, or to make it into a four-color ink with a background component.
The third problem is imposition
Previously, the imposition was the last process before platemaking. It is time-consuming and labor-intensive to finish it by hand. It is easy to cause quality problems due to slippage. Now it can be used as the last step in the DTP design, with the corresponding imposition software and a large photo-setter.
Imposition is to arrange multiple pages of electronic pages on a printed text sheet. The commonly used printing paper size is 787 x l02 mm and 850 x ll68 mm. Through computer imposition, a piece of film that meets the requirements of printed paper is produced.
In order to ensure that the printed text is cut and folded, the pages can be arranged in the correct order, and the order of the impositions should also be noted:
When binding a book, 3mm of raw edges should be cut from the sky, corner, and book mouth of the book. So when making a make-up, there is a 6mm incision between the pages. This part of the work plays a very important role in four-color printing. It is extremely difficult to try to combine 16-page 16-color four-color film on one-page printing paper, and it is much easier to use computer to complete it.
In short, color desktop publishing eliminates pure computer creation. Post-processing of electronic pages is inseparable from the separation of color and printing expertise. Designers should be aware that a considerable part of their work is professional work of plate making and printing. Only when these aspects reach a professional level can we meet the requirements of color desktop publishing design to capture the market and advance the development of color desktop publishing.