Prepress production questions (7-15)

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% C 100% M 100% Y 100% BK, that is, change the black from monochrome to four-color black.

11. What should I do if the color version and the original color version of the replacement are not set?
A: Output all the color versions again. Although this is the most stupid way, it is the safest way.

12. What is the difference between the output film and the good or upside down?
When the film is output, it is determined whether the film is facing upwards or downwards depending on whether the film is positive or negative. When a film is taken out, whether the film is facing upwards or downwards is an anti-positive film. When a negative film is selected, the medicine film is selected facing upwards to obtain a positive film. Because for the positive film, the film can be directly printed, the film surface is just in contact with the PS plate, and the printing effect is good. For the negative film, it must be copied into a positive film before the printing version, in the copy, the negative film is placed on the copy table, the film is facing up, and then stack the copy film, so that the film also happens to be in contact with the film surface To ensure copy quality. During the printing and copying process, the light source does not directly shine on the film surface.

13, what is the laser value? How to adjust?
A: The laser value refers to the amount of exposure of a row of lasers. It not only determines the density of the film on the ground and the value of the software display screen value and the output screen value of the imagesetter, but also closely relates to the life of the laser. Therefore, the control rower should select an appropriate laser value in the development and fixing conditions ( When the temperature and time are relatively fixed, the solid density D of the film is ≥ 4.0. When the percentage of dots with 50% is greater than 52%, the laser value can be appropriately reduced; when the percentage of dots with 50% is less than 48%, The laser value can be increased appropriately, and the amplitude of the laser value should be increased and decreased so that the percentage error of the halftone dot of 50% is within ±2%. Similarly, when D is less than 4.0, the laser value should be appropriately reduced when the halftone value at 50% is greater than 52%, and the laser value should be appropriately increased when the halftone value at 50% is less than 48%. . Different types of film laser exposure will be different, so each time you change the film type, the laser value should be re-tested, in the case of fixed, fixed and fixed film, the laser exposure is relatively fixed, there is not meet the requirements Places can be adjusted by linearizing 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 images of the same size and low-resolution, and there are more image information and more detailed representations. This is One of the reasons for determining image resolution considering output factors. Because of the different uses of the image, the resolution should be determined based on the use of the image. If an image is displayed on the screen, the resolution is 72Dpi or 96Dpi; if it is used for a 600Dpi printer output, it needs an image resolution of 150Dpi; to print, a high resolution of 300Dpi is required. Row. The image resolution setting should be appropriate: if the resolution is too high, the running speed is slow, and the occupied disk space is large, which does not conform to the principle of high efficiency; if the resolution is too low, the expression of the image details is affected and does not meet the principle of high quality.

15. Why does the image need to have an image file format? There are several image file formats that are commonly involved in prepress. What are their natures?
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 image formats, the format of the image should be determined based on the use of the image.
The commonly used image file formats in the design are:

TIFF format: TIFF is a tagged image file used to save the image composed of color channels. Its biggest advantage is that the image is not limited by the operating platform. It can be used universally regardless of PC, MAC or UNIX. It can save alpha channels and can store separation data in a file.

EPS Format: The EPS format is used for printing and printing. Duotone information can be saved, Alpha channels can be stored, and path and screen information can be stored.

GIF is an 8-bit format that can only express 256 colors. It is a common format for network communication images.

PSD is mainly used as an intermediate transition of image files to save the channels and layers of images for later modification. The format is so poor that only Photoshop can use it, and few other applications support it.

JPE is not only a file format, but also a compression method. This compression is lossy, loss of size is not equal, and some are small enough to be discerned by the human eye.