Frequently Asked Questions in the Printing Process (1-10)

1. When making a plate, the manuscript should be divided into four colors: green (C), magenta (M), yellow (Y), and black (K). What is the principle of color separation?

A: There are tens of thousands of colors on the screen in color drawings or color photos. It is almost impossible to print all these thousands of colors in a single color. The four-color printing method is used for printing. That is, the original is first color-decomposed and divided into four color plates of cyan (C), magenta (M), yellow (Y), and black (K), and color synthesis is performed at the time of printing. The so-called "separation" is based on the principle of subtractive color, the use of red, green and blue color filters for different wavelengths of the selective absorption characteristics of the color light, and the original is decomposed into yellow, goods, blue three primary colors. In the color separation process, the color light absorbed by the color filter is the complementary color light of the color filter itself, and the negative film forming a black and white image on the photographic film is re-screened to constitute a negative point of the screen, and the copy is finally printed in a variety of colors. Printing plate. This is the earliest photographic separation principle.

Due to the development of printing technology, we can now separate, sample, and convert the color of a manuscript into digital information by using a prepress scanning device. That is, the color of the manuscript is divided into red (R) and green (G) by the same method as photolithography. Blue (B) three colors, and digitized, and then use a computer to mathematically calculate the digital information into blue (C), magenta (M), yellow (Y), black (K) four-color information.

2. Why should prepress images be screened?

A: Because the printing process determines that the printing can only use the dots to reproduce the continuous leveling of the manuscript. If the picture is enlarged, it will be found that it consists of countless dots of different sizes. We see that dot size is different, but all occupy the same size of the spatial position. This is because once the original image is screened, the image is divided into countless regularly arranged dots, that is, the continuous adjustment of image information into discrete dots. Image information. The larger the dot, the deeper the color of the expression and the darker the layer; the smaller the dot, the lighter the color of the expression, and the brighter the level of expression. The size of the fixed space occupied by each network point is determined by the number of screen lines. For example, the number of screen points is 150 lpi, and there are 150 network points in the length or width of an inch. The location of network space and the size of outlets are two different concepts. For example, the meaning of C50% is that the size of outlets accounts for 50% of the location of the outlets, and 100% refers to the total coverage of the outlets, which is called in printing. "In the field," because there are no outlets, only 0% of the outlets are located in space, so no ink is printed on this place. Obviously, the larger the number of hanging nets is, the smaller the space occupied by the outlets is, and the more layers can be described, the more delicate they are. In fact, the level and color of the manuscript are reproduced through this method of hanging the net.

3, what is the printing color?

A: The process color is a color that consists of different percentages of C, M, Y, and K, so it's more reasonable to call it a mixed color. C, M, Y, and K are the commonly used printing four primary colors. In the printing of the primary colors, the four colors have their own color version, and the dots of the color are recorded on the color plate. These dots are generated by the halftone screen, and the four color plates are formed together. The defined primary colors. Adjusting the size and spacing of the dot-printed Internet sites can create other primary colors. In fact, the four printing colors on the paper are separated, but they are very close together. Since the resolving power of our eyes is limited, we cannot distinguish them. The visual impression we get is the mixing effect of various colors, and thus produces a variety of different primary colors.

Y, M, and C can synthesize almost all colors, but black is also needed because the black color produced by Y, M, and C is impure, and pure black is required at the time of printing, and if it is produced with Y, M, and C, There will be a problem of excessive local ink in black.

What are the equipments of the color desktop publishing system? What are the software?

A: The color desktop publishing system consists of three parts: graphic input section, graphic processing section, and graphic output section. The specific composition of each part is as follows:

(1) Graphic input device: Scanner, digital camera, computer. Software: Device driver software, and MAC and PC operating systems.

(2) Graphic processing equipment: computer. Software: 1. Computer software: Image processing software is Photoshop, Painter. 2. Graphics software: FreeHand, CorelDraw. 3. The typesetting software is PageMaker, QuarkXpress. 3D image mastering software: 3DS, Infihi-D, Strate-StudioPRO.

(3) Graphic output part of the equipment: computers, color printers, laser printers, laser imagesetters, platesetters, plate makers, etc., direct digital printers. Software: RIP, driver software, fonts.

5. Why does the computer design system need to use large-capacity memory? What are the commonly used large-capacity memories?

A: Many photos or computer-generated images are used in the design. Due to the need for print output, the image resolution is usually high, about 300 Dpi. So the image takes up a lot of disk space. For example, a 4K imposition file generally has more than 100M of all stored files. The commonly used 3.5-inch floppy disk does not meet the requirements for storing images, so large-capacity memory is used. Commonly-used large-capacity memories include: 1 magneto-optic (MO) drive, with 230M and 460M or larger discs. 2 active hard disk. 3ZIP (100M) drive. 4 rewritable discs.

6. What are the workflows for prepress design or computer design?

A: The general workflow has the following basic processes:

1 Clear design and printing requirements, accept customer data 2 Design: Including input text, images, ideas, make 3 out of black and white or color proofs, let the customer modify 4 Press the school draft modify 5 Re-release the school draft, let the customer modify until Finalization 6 After signing the customer out of the film 7 Pre-press proofing 8 Submit the proofing to the customer to see if there is a problem. If there is no problem, let the customer sign it. All work on prepress design is completed. If there is a problem in the proofing, you have to modify it and re-export the film.


7. What is the workflow for designing a computer design system?

A: The workflow in the design system is as follows: 1 First, the original is scanned according to the final size of the image, and the image is adjusted in the image software. At the same time, some creative design work can be completed.
2 In the graphics or typesetting software layout design work: including input text, draw graphics, put images.

3 After the customer finalizes the document, it sends the document to the output center to output the film. The laser imagesetter works with the Postscript language. The layout is described by the RIP (Raster Image Processor) as a bitmap and divided into four colors: C (Cyan), M (Magenta), Y (Yellow), and K (Black). sheet. If the final design requirement is not an output film, but a large-scale color inkjet sample, then the inkjet printer output is sufficient.

8, what is the density?

A: The light phenomenon of a color object generally has transmission, reflection, and selective absorption. As shown in Figure 3-20 (color), O is a color object. When the light energy of the incident light is Q in, it is selectively absorbed by the object O. The transmitted or reflected light energy is Q out. The density of the object O is: D = lg (Q out / Q in) Therefore, the density represents the nature of the amount of light absorbed by the object. The object absorbs a large amount of light and its density is high: the object absorbs a small amount of light and its density is low. Density is a common physical quantity used by the printing industry to measure the light transmittance of printed films and the depth of prints.

9. How to choose the correct output net?

A: In order to avoid collision, in theory, the color difference between the two should be 22.5 degrees, but the practice proved that the four angles of 15 degrees, 45 degrees, 75 degrees and 90 degrees works well, the yellow version of the visual stimulation Weak, poor visual sensitivity, it is generally set to 90 degrees, the most sensitive to the 45-degree angle of vision, the original main color of the original magenta or cyan is fixed at 45 degrees. For example, for the blue sky and white clouds, the cyan version should be set at 45 degrees. For the sunset and setting sun, the magenta version should be set to 45 degrees, and the magenta and blue ones should be set to a non-45 degree angle. For 15 degrees, the black version is set to 75 degrees.

10. After the file is output, only the black version has a horn. Other versions do not have horns. What should I do?

A: The only way is to re-output and change the color of the corner from 100% BK to 100%C100%M100%Y100%BK, that is, change the monochrome black to four-color black.

(to be continued)