Printing 32 FAQs
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1. When making a plate, the original is divided into four colors: cyan (C), magenta (M), yellow (Y), and black (K). What is the color separation principle?
A: There are thousands of colors on the screen, such as color drawings or color photos. It is almost impossible to print this tens of thousands of colors in one color. The four-color printing method is used for printing. That is, the original is color-decomposed into four colors of cyan (C), magenta (M), yellow (Y), and black (K), and then the color is synthesized. The so-called "separation" is based on the principle of subtractive color method, which uses the red, green and blue color filters to selectively absorb light of different wavelengths, and decomposes the original into yellow, yellow and blue primary colors. In the color separation process, the color light absorbed by the color filter is the complementary light of the color filter itself, so that on the photographic film, a negative film of the black and white image is formed, and then the screen is added to form a negative dot of the dot, and finally the color is copied and dried. Plate. This is the earliest principle of photographic color separation.
Due to the development of printing technology, we can now color, sample and convert the original color into digital information through prepress scanning equipment, that is, the original color is decomposed into red (R), green (G), and the same method as photolithography. Blue (B) three colors, and digitized, and then use the computer to mathematically decompose the digital information into four colors of c (C), magenta (M), yellow (Y), and black (K).
2. Why do pre-press images need to be added?
A: Because the printing process determines that the printing can only use the dot to reproduce the continuous tone of the original, if the image is enlarged, it will be found that there are countless dots of different sizes. We see that the dot size is different, but they all occupy the same size spatial position. This is because after the original image is screened, the image is divided into a number of regularly arranged dots, that is, the continuous image information is turned into discrete dots. Image information. The larger the dot, the darker the color and the darker the layer; the smaller the dot, the lighter the color, and the brighter the layer. The fixed spatial position occupied by each dot is determined by the number of screen lines. For example, if the mesh point is 150 lpi, there are 150 dots in the length or width of one inch. The location of the dot space and the dot size are two different concepts. For example, C50% means that the dot size accounts for 50% of the dot space position, and 100% means that the dot size covers the dot space position, which is called "printing". In the field, 0% has no dots, only the dot space, so no ink is printed in this place. Obviously, the larger the number of nets, the smaller the space occupied by the dots, and the more layers that can be described, the more delicate. In fact, the level and color of the original are reproduced through this method of hanging nets.
3. What is the printing color?
A: The printing color is a color composed of different percentages of C, M, Y, and K, so it is more reasonable to call it a mixed color. C, M, Y, and K are the four primary colors used in printing. When printing the primary colors, these 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 combined to form. The primary color defined. Adjusting the size and spacing of the color grid points will create other primary colors. In fact, the four printed colors on the paper are separate, but they are very close. Because our eyes have a certain ability to distinguish, we can't distinguish them. The visual impression we get is the blending effect of the various colors, thus producing a variety of different primary colors.
Y, M, C can synthesize almost all colors, but still need black, because the black produced by Y, M, C is impure, requires more pure black when printing, and if Y, M, C are used to produce Black will have too much local ink problem.
4. What are the devices for the color desktop publishing system? What are the software?
Answer: The color desktop publishing system consists of three parts: graphic input part, graphic processing part and graphic output part. The specific components of each part are as follows:
(1) Graphic input part of the device: scanner, digital camera, computer. Software: Device driver software, and operating systems for MAC and PC.
(2) Graphic processing part of the device: computer. Software: 1. Computer software: Image processing software is Photoshop, Painter. 2. The graphics software is: FreeHand, CorelDraw. 3. The typesetting software is PageMaker, QuarkXpress. 3D image editing software: 3DS, Infihi-D, Strade-StudioPRO.
(3) Graphic output part equipment: computer, color printer, laser printer, laser imagesetter, direct plate-making machine, plate-making machine, etc., direct digital printing machine. Software: RIP, driver software, font library.
5. Why does the computer design system need to use large-capacity memory? What are the commonly used mass storage?
A: Many photos or computer-generated images are used in the design. Because of the need for print output, the resolution of the image is usually high, about 300Dpi. Therefore, the disk space occupied by the image is large. For example, a 4K imposition file, generally all storage files should exceed 100M. The commonly used 3.5-inch floppy disk does not meet the requirements for storing images, so large-capacity memory is used. Commonly used mass storage devices are: 1 optical disk (MO) drive with 230M and 460M or larger. 2 active hard drives. 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, imposition 3 out black and white or color proof, let customers modify 4 according to the revision of the manuscript 5 again, release the proof, let the customer modify, until Finalized 6 Let the customer sign out and then go out to the film. 7 Pre-press proofing 8 Send the proof to the customer, let the customer see if there is any problem, if there is no problem, let the customer sign. All pre-press design work 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 the computer design system to complete the design?
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, and some creative design work can be completed.
2 Typographic design work in graphics or typesetting software: including inputting text, drawing graphics, and placing images.
3 After the customer has finalized the document, send the file to the output center to output the film. The laser imagesetter works in the PostScript language. The RIP (Raster Image Processor) describes the layout as a bitmap image and is divided into C (cyan), M (magenta), Y (yellow), and K (black). sheet. If the final requirement of the design is not the output film, but a large color inkjet sample, the output can be done with the inkjet printer.
8. What is 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, it is selectively absorbed by the object O. The light energy transmitted or reflected is Q. Then the density of the object O is: D = lg (Q out / Q in). Therefore, the density indicates 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 amount of light absorbed by the object is small, and its density is low. Density is a common physical quantity used by the printing industry to measure the light transmittance of a film and the color depth of a printed product. Greater China Graphic Arts Network
9. How to choose the correct output corner?
A: In order to avoid hitting the net, in theory, the difference between the colors should be 22.5 degrees, but the practice shows that the four angles of 15 degrees, 45 degrees, 75 degrees and 90 degrees are very good, and the yellow version is a visual stimulus. It is weak and has poor visual sensitivity. Therefore, it is generally set at 90 degrees. The vision is most sensitive to the 45-degree angle. Generally, the main color of the original is magenta or cyan is 45 degrees. For example, for the blue sky and white clouds, the blue version should be set to 45 degrees. For the morning glow and the sunset, the magenta version should be set to 45 degrees, and the magenta and blue non-45 degree angles can be set. For 15 degrees, the black version is set at 75 degrees.
10. After the file is output, only the black version has a corner line. Other versions have no corner lines. 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.
11. What should I do if the color version and the original color version are inaccurate?
A: Re-export all the color plates. Although this is the most stupid way, it is the safest way.
12. When outputting film, is it better to choose the film face up or down? What is the difference?
When the film is output, it is determined whether the film is facing up or down, depending on whether the film is positive or negative. When the film is released, the film is selected to face up or down, and the anti-positive film is obtained. When the negative film is taken out, the film is selected to face upward, and the positive film is obtained. Because for the positive film, the film can be directly printed, the film surface is just in contact with the PS plate, and the effect of the printing plate is good. For the negative film, it must be copied into a positive film before printing. When copying, the negative film is placed on the copying table, the film is facing up, and the copy film is stacked on top, so that the copy film is also in contact with the drug film. To ensure the quality of the copy. During the printing and copying process, the light source is not directly irradiated on the film surface.
13. What is the laser value? How to adjust?
A: The laser value refers to the amount of exposure of the laser. It not only determines the density of the film in the field and whether the software display dot value is consistent with the output point value of the imagesetter, but also closely related to the life of the laser. Therefore, the control machine should select a suitable laser value in the development and fixing conditions ( Under the condition of relatively fixed temperature and time, the film solid density D is ≥4.0, when the percentage of 50% dot is greater than 52%, the laser value can be appropriately reduced; when the percentage of 50% dot is less than 48%, The laser value can be appropriately increased, and the amplitude of the laser value should be increased and decreased so that the 50% dot percentage error is within ±2%. Similarly, when D is <4.0, when the dot value at 50% is greater than 52%, the laser value should be appropriately reduced. When the dot value at 50% is less than 48%, the laser value should be appropriately increased. . Different types of film laser exposure will be different, so each time you change the film model, the laser value should be re-tested. When the development, fixing and film are fixed, the laser exposure is relatively fixed, and there is no requirement. The place can be adjusted by the linearization of the film.
14. What is the image resolution? Why emphasize it?
A: The resolution of printed images has been introduced in the basic part of printing. We know that high-resolution images contain more pixels than the same-sized low-resolution images, and the image information is more and the details are clearer. One reason to determine the image resolution is to consider the output factor. Since images are used for different purposes, the resolution should be determined based on the purpose of the image. If an image is displayed on the screen, the resolution is 72Dpi or 96Dpi; if it is used for 600Dpi printer output, it needs 150Dpi image resolution; if printing, it needs 300Dpi high resolution. Row. The image resolution setting should be appropriate: if the resolution is too high, the running speed is slow, the disk space occupied is large, and the efficiency principle is not met; if the resolution is too low, the expression of the image details is not in accordance with the high quality principle. Greater China Graphic Arts Network
15. Why do images need to have an image file format? There are several image file formats that are often involved in prepress. What is the nature of each?
A: The image file format determines what type of information should be stored in the file, how the file is compatible with various application software, and how the file exchanges data with other files. Since there are many formats for images, the format of the image should be determined according to the purpose of the image.
The image file formats commonly used in design are:
TIFF format: TIFF is a tagged image file that holds an image composed of color channels. Its biggest advantage is that the image is not limited by the operating platform, and can be used regardless of PC, MAC or UNIX. It can store alpha channels and store color separation data in a single file.
EPS format: EPS format is used for printing and printing. It can store Duotone information, store Alpha channel, and store path and screen information.
GIF is an 8-bit format that can only express 256 colors. It is a common format for network propagation images.
PSD is mainly used as an intermediate transition of the image file to save the channel and layer of the image for later modification. The format is poorly versatile, and only Photoshop can use it, and few other applications support it.
JPE is both a file format and a compression method. This compression is lossy, and the loss varies in size, and some are too small to be discerned by the human eye.
16. What is the number of screens for printing images? What is the relationship between image resolution, scanning resolution, and laser imagesetter output resolution?
Answer: Since the printed matter is composed of dots, the number of screened lines in the printed image refers to the number of lines per inch of the printed matter in the horizontal or vertical direction, that is, the number of hanging nets. The number of screens is called because the earliest printed dots are wired. The unit of the number of hanging lines is Line/Inch (LPI). For example, 150Lpi means that there are 150 network cables per inch. Adding a picture to the image, the larger the number of nets, the more the number of nets, the denser the nets, and the richer the level of expressiveness.
Because the computer image is a dot matrix, that is, one pixel (the smallest unit of the image is called a pixel). The image resolution can be visually understood as how many pixels are represented by a line within a unit length in the horizontal or vertical direction. The more pixels used to describe the line, the higher the resolution. The unit of image resolution is generally Pixels
PerInch (pixels per inch), usually expressed in English as PPI. For example, if an image has a resolution of 300 PPI, it means that it has 300 pixels per inch in the horizontal or vertical direction; if the resolution of an image is 720I, it means that it has 72 pixels per inch in the horizontal or vertical direction.
Some devices have resolutions similar to those of images, except that they are expressed in dots, so they are represented as Dot Per Inch, or DPI for short. For example, an image scanner with a resolution of 1200 DPI has an image input accuracy of 1200 dots per inch, or pixels. The 3600DPI laser imagesetter has a graphic output accuracy of 3,600 laser dots per inch.
The image resolution PPI and the printing resolution LPI (the number of screen lines) are related and different: the image resolution is higher than the printing resolution, generally 2 × 2 pixels generate 1 dot, that is, the LPI is DPI About one-half.
17. What are the types of scanners?
A: 1 roller scanner: divided into high-end roller scanner and small desktop roller scanner.
2 flatbed scanner: three grades of high, medium and low, as high- and mid-range scanners for printing design.
3 hand-held scanners for offices and more.
4 film and transparent media scanners. Used to digitize positive and negative 35mm. Greater China Graphic Arts Network
18. What are the commonly used output devices? What is the field of their respective applications?
A: The designed page electronic file can be output by the following devices:
1. Black and white laser printer: used to print black and white proofs or final black and white drafts.
2. Color laser printer: used to print color effects or final color masters.
3. Color inkjet printer: used to print color effects.
4. Color Large Inkjet Printer: For printing large color effects or final color drafts.
5. Digital proofer: used to check the content and color of the page.
6. Laser imagesetter: used to output film sheets for printing.
7. Direct plate making machine: used to output printing plates.
8. Digital printing machine: prints directly from an electronic page. There is no need for film and plates.
19. What types of scanners are there? What's the difference?
A: There are two types of scanners: one is a roller scanner; the other is a flatbed scanner, which can be divided into high-end professional scanners and low-end flatbed scanners. The roller scanner is developed by an electronic color separation machine. The sensing technology is a photomultiplier tube, and Figure 5-1 is a working principle diagram of the roller scanner. The flatbed scanner is scanned by a CCD device. The different working principles determine the difference in performance between the two scanners:
(1) The highest density range is different: the highest density of the roller scanner can reach 4.0, while the average low-end flatbed scanner is only about 3.0. As a result, the roller scanner can sweep out more detail in the dark, and improve the contrast of the image.
(2) Different image clarity: The roller scanner has four photomultiplier tubes: three for color separation (red, green, and blue) and one for virtual mask. It can make the unclear object become clearer and improve the sharpness of the image, while the CCD does not have the function of this main surface.
(3) The image has different degrees of detail: after the image scanned by the photomultiplier tube is printed and printed, the details are clear, the dots are fine, and the texture is small, and the quality of the photo scanned by the flatbed scanner is relatively poor in terms of image fineness. some.
20. What is the Pantone color? Why use Pantone to set the color?
A: Pantone is a famous ink brand in the United States and has become a standard for printing colors. It uses all the inks produced by it to make chromatograms and color standards. Pantone's color code has become a recognized language for color communication. Users need a certain color and they can be calibrated according to color code. Due to the widespread use of the Pantone color code, the computer design software has a Pantone color library and uses it for color definition. When setting the color using the Pantone color library, the selection method is Pantone color, but it should be noted that most Pantone colors are spot colors. If you want to reproduce them in four colors, set the color type to the primary color. Figure 1-13 is an interface that defines the Pantone color.
21. What is color separation? Is color separation so important? How to color separation in Photoshop?
A: Separation is a printing term that refers to the decomposition of various colors on the original into four primary colors: yellow, magenta, cyan, and black. In computer-printed design or graphic design image software, color separation works. It is to convert the color mode of the scanned image or other source image into CMYK mode.
Generally, the scanned image is in RGB mode, and the image taken with a digital camera is also in RGB mode. Most of the images downloaded from the Internet are in RGB color mode. If you want to print, you must divide the color into four colors: yellow, magenta, cyan, and black. This is the requirement for printing. If the image color mode is RGB or Lab, it is possible to output only the dot on the K version, that is, the RIP interpretation only interprets the color information of the image as gray.
In Photoshop, the color separation operation is actually very simple: you only need to convert the image color mode from RGB mode or Lab mode to CMYK mode. The specific operation is to execute Image/Mode/CMYK. Thus the color of the image is represented by the colorant (ink), with a channel of 4 colors. When the image is output, the dots will be generated according to the channel data of the color, and divided into four color separation films of yellow, magenta, cyan and black.
22. In the color separation, when the image is transferred from RGB to CMYK, the naked eye can see that some colors on the screen will change significantly. What is the reason? What is the effect on the color of the image?
A: When the image is changed from RGB color mode to CMYK color mode, some bright colors on some images will change significantly. This change can be observed obviously, and it will change from bright color to dim. Some colors. This is because the color gamut of RGB is larger than the color gamut of CMYK, which means that some colors that can be represented in RGB color mode are beyond the range of colors that CMYK can express after switching to CMYK. These colors can only be Replace with similar colors. Thus these colors produce a more pronounced change. In fact, if there is color in the RGB color mode image beyond the color gamut, you can use Gamut Warning to preview.
23. What is the gamut space? What is the meaning of gamut space?
We edit images in RGB, CMYK, and Lab, the essential difference being working in different gamut spaces. The gamut refers to the range of colors that can be expressed by a certain color pattern. It also refers to the range of colors that can be expressed by specific media such as screen display, printer output, and print copy. The color of the visible spectrum in nature constitutes the largest gamut space, which contains all the colors that the human eye can see. In color mode, the Lab gamut has the largest space, and it contains all the colors in RGB and CMYK.
24. What mode is better for the color mode of the design image?
A: In Photoshop, the image's color mode has RGB mode, CMYK mode, GrayScale mode and other color modes. The use of any mode for designing an image mode depends on the end use of the design image. If the designed image is to be printed or printed on printed paper, it is best to use the CMYK color mode so that the color seen on the screen is closer to the output print color or the printed color. If the design is for electronic media display (such as web page, computer projection, video, etc.), the color mode of the image is best to use RGB mode, because the color of RGB mode is more vivid and richer, and the picture is better. And the image has only 3 channels, the amount of data is smaller, and the disk space is also small. If the image is gray, it is better to use the GrayScale mode, because even if the image is expressed in RGB or CMYK color mode, it still looks like a neutral gray color, but its disk space is much larger. In addition, if the gray image is to be printed, if it is expressed in CMYK mode, there are 4 editions in the film and printing. The cost is not big, and it may cause the color cast problem when the gray balance control is not good during printing. When the amount of ink is too large, the gray image will be colored.
25. How is gold and silver printed? What are the requirements for prepress design?
A: In the design, customers often require gold and silver printing. Since gold and silver cannot be realized by four-color printing, their printing and technology have special requirements. When printing, gold and silver are processed according to the spot color, that is, printing with gold ink and silver ink, so the film should also be a spot color film, a film film alone, and printing separately.
When designing a computer, you should define a color to represent gold and silver, and define the color type as a spot color to meet the design requirements. Since gold, silver and silver are opaque, gold and silver content can be set to Overpint when designing.
26. What is spot color and spot color printing?
A: Spot color means that when printing, instead of printing C, M, Y, K four colors to synthesize this color, it is specifically used to print the color with a specific ink. Spot color inks are pre-mixed by the printing house or produced by the ink factory. For each spot color of a print, there is a special color version corresponding to the print. Use spot colors to make colors more accurate. Although the color cannot be accurately represented on the computer, the pre-printed color sample card of the standard color matching system can see the exact color of the color on the paper. For example, the Pantone color matching system creates a very detailed color sample card. .
For non-standard spot color colors set in the design, the printer does not necessarily accurately allocate it, and the exact color cannot be seen on the screen, so do not use your own defined spot color if it is not a special requirement.
27. What are the common color schemes used in computers? What is the best way to define colors in general?
A: A method is needed to describe different colors, whether on a computer or when printing. The color method is also called color model or color mode. There are many types of color models, each of which can describe colors from different angles, but different color modes are suitable for different situations and the accuracy is different.
Computer color mode
1, RGB mode: also known as RGB color space. It is a color-light color mode that is widely used in our lives, such as televisions, computer monitors, slides, etc., which use light to color. Scanning and publishing often requires scanning images. The first thing the scanner extracts is the RGB color information on the original image. The RGB mode is an additive color mode, and any color can be described by the amount of radiation of R, G, and B. When the computer defines the color, the three components of R, G, and B have a value range of 0-255, 0 means no stimulation amount, and 255 means maximum stimulation amount. When R, G, and B are both 255, white light is synthesized, and when R, G, and B are both 0, black is formed. This mode is often used when displaying color definitions on the display. Images such as TV, slideshow, network, multimedia, generally use RGB mode.
2. CMYK mode: also known as CMYK color space. For those who work in the printing industry, CMYK is the most familiar. This mode is a subtractive mode that follows the subtractive method and the law. The CMYK mode essentially refers to the C, M, Y, and K dot sizes printed when the color is reproduced, so the values of C, M, Y, and K range from 0% to 100%. CO%MO%YO%KO% indicates white, and C100%M100%Y100%K100% indicates black.
3, HSB mode: hue (HUE), saturation (Saturation), brightness (Brightness) mode.
28. Since the RGB image is better than the CMYK image, the color is more beautiful. Can you output the RGB image directly? What are the consequences of doing this?
A: Since the color gamut of RGB is larger than CMYK, some colors are displayed on the screen, but the four-color ink is not printed. If you want to know the consequences, just give it a try. Due to the difference of RIP, the RGB image may only have a picture on the black color on the color separation film, and there is no picture on the other color version. It is also possible that the information (mesh point) of the picture on the four color film is exactly the same, that is, the gray image of the equivalent value. Although some distribution software or RIP can convert RGB to CMYK, it is best to use scan software or Photoshop for mode conversion.
29, save the color map as DCS format, there are pictures when printing black and white, but there is no picture on the output film. Why is that?
A: Saving the image as a DCS format will result in five files.
30. What is RIP? Why do you like to use software RIP now?
A: RIP is the abbreviation of RasterProcessing. It refers to the software or hardware card that interprets PostScript code as bitmap image in the photo system. It is generally called raster image processor. It plays an important role in the color publishing system. Its function is to quickly interpret the produced page as a command to control the output point of the laser recorder. It can automatically convert the text, graphics, images and other elements in the page. Digital dot matrix information, and then use this information to control the output device for recording, whether its work is "off" or "on".
The replacement of hardware RIP requires complex technology and long time, and can not adapt to the rapid development of software technology; and software RIP is widely used because of its fast update, high processing quality, high speed, and display of post-processing results. And a software RIP can drive multiple imagesetters at the same time, and the network function is strong.
31. Why not set the resolution in typesetting and graphics software?
A: The typesetting graphics software is object-oriented software. The representation of text and graphics is expressed in the language of the algorithm. The objects produced are independent of resolution. They are output at the output of the output device. If the output device has a high resolution, the image output resolution of the created page is high. Therefore, graphics software and typesetting software do not need to set the resolution. The image imported in the typesetting and graphics software will read the dot matrix information of the original image when it is output, which is related to the resolution of the original image.
32. How many types of text in CorelDraw?
A: CorelDraw divides text into two different types, one is art text and the other is paragraph text. Although both texts are created using text tools, they have different characteristics, and the text is With more graphical object features, you can apply more special effects to the art text; while paragraph text can use more text formats. Based on the different characteristics of the two types of text, they can be used for different purposes. If you only need to use a small amount of text or apply more formatting to the text, such as a short title and description, you can use the word text; You need to process a large amount of text to apply more formatting, such as newspapers, brochures, etc., you can use paragraph text.