FAQ 1 in the hottest printing process

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FAQ during printing (1

1. During plate making, the original should be divided into four colors: cyan (c), magenta (m), yellow (y) and black (k). What is the color separation principle

answer: there are thousands of colors on the picture of color paintings or color photos. It is almost impossible to print these thousands of colors in one color. The printing method is four-color printing. That is, first decompose the original into cyan (c), magenta (m), yellow (y) and black (k) four-color plates, and then synthesize the colors during printing. The so-called "color separation" is to use the selective absorption characteristics of red, green and blue color filters to different wavelengths of color light according to the principle of subtraction to decompose the original into three primary colors: yellow, magenta and green. In the process of color separation, the color light absorbed by the color filter is the complementary color light of the color filter itself, so that on the photosensitive film, a negative film of black-and-white image is formed, and then added to form a point negative film, and finally copied and dried into various color printing plates. This is the earliest principle of photographic color separation

due to the development of printing technology, now we can use prepress scanning equipment to separate, sample and convert the original color into digital information, that is, using the same method as photographic plate making, we can decompose the original color into red (R), green (g) and blue (b), and digitize it, and then use the computer to decompose the digital information into green (c), magenta (m), yellow (y) and black (k) through mathematical calculation

2. Why should prepress images be added

answer: because the printing process determines that printing can only use dots to reproduce the continuous gradation of the original. If you zoom in, you will find that it is composed of countless dots of different sizes. We can see that although the point sizes are different, they all occupy the same space position. This is because once the original image is added, the image is divided into countless regularly arranged points, that is, the continuous tone image information is changed into discrete point image information. The larger the point, the darker the color and the darker the layer; The smaller the point is, the lighter the color is, and the brighter the level is. The size of the fixed space occupied by each point is determined by the number of lines added. For example, if the number of points added is 150lpi, there are 150 points in the length or width of an inch. Point space position and point size are two different concepts. For example, C50% means that the point size accounts for 50% of the point space position, and 100% means that the point size all covers the point space position, that is, the so-called "field" in printing. 0% because there is no point, there is only the point space position, so there is no ink printed on this place. Obviously, the larger the number of hanging eyes, the smaller the space occupied by the point, and the more layers that can be described, the more delicate. In fact, the level and color of the manuscript are reproduced through this hanging method

3. What is printing color

answer: printing color is the color composed of different percentages of C, m, y and K, so it is more reasonable to call it mixed color. C. M, y and K are the four primary colors commonly used in printing. When printing primary colors, these four colors have their own color plates, and the points of this color are recorded on the color plate. These points are generated by the halftone screen, and the defined primary colors are formed by combining the four color plates. Adjust the size and spacing of points on the color plate to form other primary colors. In fact, the four printing colors on the paper are separated, but they are very close. Because our eyes have certain restrictions on the ability to distinguish, we can't distinguish them. The visual impression we get is the mixing effect of various colors, resulting in various primary colors

y, m, C can synthesize almost all colors, but black is also needed, because the black produced by Y, m, C is impure, and a purer black is needed during printing, and if y, m, C are used to produce black, there will be too many local inks

4. What are the devices of the color desktop publishing system? What are the software

answer: the color desktop publishing system consists of three parts: image and text input part, image and text processing part and image and text output part. The specific composition of each part is as follows:

(1) the equipment of image and text input part: scanner, digital camera, computer. Software: device driver software, and MAC and PC operating systems

(2) graphics and text processing equipment: computer. Software: 1. Computer software: image processing software is Photoshop and painter. 2. Graphics software: freehand, CorelDRAW. 3. The typesetting software is PageMaker and QuarkXPress. Three new materials can respond to electrical signals. Dimensional image making software: 3DS, infihi-d, strate studiopro

(3) image and text output equipment: computer, color printer, laser printer, laser Imagesetter, direct plate making machine, plate punching machine, etc., direct digital printer. Software: Rip, driver software, word library

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

answer: many photos or computer-made images are used in the design. Because of the need of printing output, the resolution of the image is usually high, about 300dpi. Therefore, images occupy a lot of disk space. For example, for a 4K patchwork file, generally all stored files should be more than 100m. The 3.5-inch floppy disk usually used cannot meet the requirements of storing images, so large capacity memory is used. Common mass storage devices include: ① optical disk (MO) drives, with disks of 230m and 460m or larger. ② Active hard disk. ③ Zip (100m) drive. ④ Rewritable disc

6. What are the workflow of prepress design or computer design

answer: the general workflow has the following basic processes:

① clarify the design and printing requirements, and accept customer information ② design: including input text, images, creativity, and typography ③ issue black-and-white or color proofreading, and let the customer modify ④ modify according to the proofreading ⑤ issue proofreading again, and let the customer modify, The difference between ZhiBei Thermal Power Co., Ltd. and Nanfang hydropower Co., Ltd. is particularly obvious until the final version ⑥ let the customer sign and then issue the film ⑦ prepress proofing ⑧ send it to the printing proofing, let the customer see if there is a problem, if there is no problem Shanghai), let the customer sign. All the pre press design work is completed. If there is a problem in proofing, you have to modify it and re output the film

7. What is the workflow of the computer design system to complete the design

answer: the workflow in the design system is as follows: ① first, scan the original according to the final size of the image, adjust the image in the image software, and complete some creative design work at the same time

② carry out typesetting design in graphics or typesetting software: including inputting text, drawing graphics, and placing images

③ after the customer finalizes the document, send the document to the output center to output the film. The laser Phototypesetter works in postscript language. The layout is described as a lattice image by Rip (raster image processor), and is divided into C (cyan), m (magenta), y (yellow) and K (black). If the final requirement of the design is not to output the film, but a large-scale color inkjet sample, it can be output by the inkjet machine

8. What is density

answer: light phenomena of color objects generally include transmission, reflection and selective absorption. As shown in the figure (color), O is an object with extremely high color requirements, such as color. When the light energy of the incident light is Q input, it is selectively absorbed by object o. The transmitted or reflected light energy is Q output. Then the density of object o is: d=lg (Q out/Q in), so the density represents the nature of the amount of light absorbed by the object. If an object absorbs a large amount of light, its density will be high; if an object absorbs a small amount of light, its density will be low. Density is a commonly used physical quantity in the printing industry to measure the light transmittance of film and the color depth of printed matter

9. How to choose the correct output angle

answer: in order to avoid collision, in theory, the difference between match colors should be 22.5 degrees, but practice has proved that the four angles of 15 degrees, 45 degrees, 75 degrees and 90 degrees are very good. The yellow version has weak visual stimulation and poor visual sensitivity, so it is generally set at 90 degrees, and vision is the most sensitive to 45 degrees. Generally, the main color of the original magenta or green is set at 45 degrees. For example, for the picture of blue sky and white clouds, the green version should be set at 45 degrees, for the picture of sunrise and sunset, the magenta version should be set at 45 degrees, the non 45 degree angle between magenta and green can be set at 15 degrees, and the black version should be set at 75 degrees

10. After the file is output, only the black version has a corner line, and other versions have no corner line. What should we do

answer: the only way is to re output, and change the color of the corner line from 100%bk to 100%c100%m100%y100%bk, that is, from monochrome black to four-color black

(to be continued)

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