Plane Output (Printing) Precautions (6-9)

6. Principle of lithographic printing

There are several types of printing methods, such as offset printing, letterpress printing, and gravure printing, etc. China's book and packaging printing currently uses letterpress printing, while foreign letterpress printing has been replaced by lithographic printing. Compared with letterpress printing and gravure printing, lithographic printing technology has its unique features and is summarized as follows:
1) The practical application of the natural law of oil and water immiscibility in lithography. Lithography uses the laws of water and oil incompatibility to achieve the purpose of printing. At present, lithography is still inseparable from water
2). The lithographic printing plate, the blank part and the graphic part utilizes the law of water and oil immiscibility almost on the same plane of the printing plate, through the technical treatment, forms the lipophilic hydrophobicity on the printing plate of the same plane. The graphic part and the blank part of the hydrophilic oleophobic. In the printing process, the wetting mechanism first applies a uniform amount of water to the blank portion of the printing plate, and the blank portion does not absorb the ink, and then the ink is used to make the graphic portion absorb an appropriate amount of ink, and the graphic is completed by the embossing mechanism. Transfer the copy to achieve the purpose of printing.
3). The lithographic printing method is an indirect printing. The pattern on the printing plate is "formal". The ink on the lithographic printing plate is not directly transmitted to the paper, but is transferred to the blanket cylinder first. The ink is then transferred to the printing material, so the graphic is "informal" indirect printing. The rubber blanket wrapped on the surface of the blanket has two characteristics: First, it has better hydrophobic and oleophilic characteristics, it can fully transfer ink, and restrict the transmission of moisture. Second, the blanket has elasticity and can be larger. In the case of printing pressure and compressive deformation, the imprint of the solid surface enlargement rate is small.
4). Dot fineness - The color of the flat-printing products is ever-changing, beautiful, and the formation of its color is made up of network dots and color inks, and the dot fineness is the main one. It is guided by the light color theory. The overlapping, parallel means of the dots are based on the theory that the three primary colors or the three primary colors plus black (four colors), through the photo separation or electronic color separation, decompose the color of the picture into yellow, magenta, cyan, black, etc. with different reticulation angles. Color version, and then use four-color printing plate, overprinting overlap to reproduce numerous levels and colors, to obtain very colorful art replicas.
5). Multi-color printing, wide range of printing format - lithographic printing can print monochrome text version, but mainly multi-color printing. The printing format can be large or small (four-on-two-sheets) and can also be printed with multi-colored products on the screen and on the field. The finished product is flat and colorful, which is not comparable to other printing methods. The graphic part and the blank part of the lithographic printing plate are on the same plane. The two parts have completely opposite properties for the water and oil intimacy. The graphic part is oleophilic and hydrophobic, while the blank part is hydrophilic and oleophobic. The role of the graphic part is to adsorb the ink to reject the fountain solution. During the printing process, the blank part is first moistened by the fountain solution, and then the graphic part is coated by the ink, and then the graphic part of the ink is transferred to the paper. Lithography is based on the principle of immiscibility between oil and water, transferring the graphic on the plate to the paper.

7. Simplify the EPS image

If you want to say the final reason, in the PostSript file, the overly complicated path is the culprit that makes the file not print correctly. Too many nodes with paths or smooth settings will increase the complexity of the file, causing the laser printer or imagesetter to crash, resulting in fatal "Limitcheck" or "VMError" PostSript errors. In particular, when sending files to high-resolution output devices, you should split complex paths and set high smoothness in Illustrator or Macromedia, or use the eeHand instruction to simplify the path. When using Adobe Streamline strokes, use path simplification to reduce path complexity. Use high tolerance readings in Photoshop to reduce the number of nodes when the selection becomes a clipped path. Do not nest EPS images in other EPS files. Like this: Several EPS images are imported into an Illustrator file, stored as EPS, placed on a QuarkXPress page, stored as an EPS, and placed into another QuarkXPress file. If you are lucky, that file happens to print. However, as each layer is put into the EPS, the chance of success will be less and less. If you have to convert a full-page QuarkXPress EPS to a file that can be dot-patched by Photoshop. Let Photoshop turn the file into a bitmap and save it as Photoshop's EPS or TIFF. Neither of these two formats adds extra layers to the PostSript language.

8. Smooth the gradient

Gradients using mathematical operations by QuarkXPress and Illustrator work well over short distances of a few inches, but if you try to make a subtle gradient of the entire page, PostSript's limit may lead to a banding effect, and the gradient will be in Photoshop. Make a bitmap (using Add Noise) and enter it in other applications. However, you can't use Photoshop to handle layers made in Illustrator. Compared to gradients created directly in the Photoshop palette, Illustrator files processed by Photoshop do not produce the ideal intermediate gradient.

9. Use a good font

Many output centers do not want to see TrueType words. PostSript has become a standard. TrueType usually has the same word name as the corresponding PostSript word, causing conflicts. TrueType must be manually downloaded into the RIP of the imagesetter. This is a time-consuming task. Contact the export center in advance. Do not use font commands to create bold or italic effects. It is best to select the desired font effect directly from the application font menu. If the font does not have the desired bold or skewed effect and the font command is used, the MAC will forge a bold or italic effect for each character - but this is only on the screen. If it is output on the printer, the final printing effect looks as if it has not been used at all. So what's the effect of using the underline? Don't use fonts that do not have the effect that the font itself has. If you are using a beautiful serif or fine-brushed font (Bodoni is a good example), and the size of the word is set to be very small, do not separate the words. Otherwise, even slight misalignment of the plates will cause overprinting of the most sensitive parts.