Problems needing attention before the output of th

2022-08-01
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Problems needing attention before exporting parts

I Scanning color separation

the scanner calibration principle is to adjust the scanner to be able to faithfully copy the tone level information, color change and gray balance of the original. The specific method is to use a special emission or transmission color code to adjust the highlight, dark tone value and the gamma value of the intermediate value in the scanning software. If necessary, adjust the RGB or CMYK single channel value to make the tone, color and gray balance of the electronic image consistent with the color code. The operation steps are as follows:

1 After the scanner is turned on and stabilized for more than ten minutes, place the standard color code in the scanning area, start the scanning software, and scan with the default parameters

2. After scanning, use a probe to measure the color data of the gray ladder in Photoshop. Adjust the high light value and dark tone value in the scanning software as required, so that the first level of the gray scale is between 250 and 255, and the second level of the dark tone is between 0 and 5. If the dark tone value is large after scanning, it indicates that the dark tone is not enough. You can increase the dark tone value from 0 to a larger value to ensure that the value of level 22 is equal to or smaller than 5. Of course, the calibration of the white field is the same. Between the 19th and 22nd levels, there is little difference between the values, which is about 10. The dark tone level is not opened, and the tone is compressed and lost. This is determined by the performance of the scanner itself and has little effect on most originals. For originals with rich dark tone levels, it is recommended to scan with a roller scanner

3. Adjust the gamma value of the intermediate adjustment so that the 11th level value of the gray scale is about 125. If the value of level 11 is too small, increase the gamma value; Otherwise, decrease the gamma value

4. According to the relationship between the RGB values of each gray scale, adjust the values of the three in a single channel so that the values of each scale in the three channels are roughly equal. If r=g=125 and b=119 occur, increase the gamma value of channel B to make it not yellow. The scanned RGB image can be output only after it is converted to CMYK by color separation. During this period, the color separation correction shall be carried out for the image

II Graphics and image processing and edition composition

1 Color separation parameter setting mainly includes printing ink setting and color separation setting

(1) setting of printing ink

① if coated paper is used for printing, the ink can be Toyo inks or swop inks. Other parameters can be determined according to the specific paper

② dot gain refers to the enlargement of the point at 50% of the middle adjustment. If it is printed on coated paper, it is recommended to take 12% ~ 15%; If printing on offset paper, use 15% ~ 20%; 20% ~ 25% if printed on paper. The larger the value is set, the smaller the CMYK data after color separation

③ gray balance refers to the value of ink gray balance during printing. This value is available to every printing house

④ use point enlargement of gray image. Point, the gray image will change according to the compensation of point expansion. The larger the point enlargement value, the darker the display. Giving this option will also affect the conversion data from other modes to grayscale mode. For example, when converting a gray-scale image from RGB, which is unique in many disciplines and fields, the software will automatically call the point expansion value to compensate the value of the gray-scale image. The larger the point enlargement value, the smaller the gray image data

(2) for color separation setting, select the separation set up option under file/preference

① select the color separation type. There are two color separation types, GCR and UCR. One at a time. GCR is ash composition substitution; UCR is background color removal. The background color removal here is different from the previous background color removal on the electric unit, so it is recommended to use the GCR mode

② determine the black generation curve of the black version. When there are not many gray components in the image (such as landscape pictures, portraits, etc.), the black version is usually set as the middle note black version; If the image is an art photography with high saturation and high contrast, the black version can be set as a short black version with high contrast; When there are many gray elements in the image (such as the old paintings), the long tone black version is used

③ black limit different types of originals should have different values, ranging from 70% to 90%, generally 85%

④ the setting of total ink amount (Title ink limit) indicates the maximum value of the sum of four color dots. For example, 340% ~ 380% for offset printing with coated paper; Paper is about 260%

⑤ UCA amount this value mainly increases the value of CMY at the dark tone. For originals with rich dark tone levels, the value can be larger, such as 40%; Otherwise, the smaller the better

2. Color correction

photoshop mainly processes the scanned output pictures from two aspects: panchromatic correction and selective correction. For panchromatic correction, the curves curve can be used to correct the high and dark tone values, taking into account the gradient and gray balance of the image; For selective color correction, the local color block in the figure can be adjusted as necessary. The adjustment amount should not be too large, otherwise it is easy to produce hierarchical faults. After the graphics and images are processed, the edition can be assembled by the edition software. After the edition is assembled, the output and layout can be carried out, that is, the film is ready to be produced

III Output scheduling

output scheduling relies on rip technology. That is, raster image processor, which can convert graphics, images and text information into page language understood by various large format printers or phototypesetters, so as to complete output. It can control the printing accuracy, color and format size. No matter what kind of rip, there are two technologies for converting electronic documents into printing languages: one is color separation; Second, add. The color separation is generally four colors, and sometimes there is a spot color. The standard test method for structural performance of external windows, curtain walls and doors under the action of uniform static air pressure difference ASTM E330 (1) 999 is more. Rip can be divided into hardware and software. The hardware Rip is built into the printer imagesetter or a special hardware rip chassis; Software rip includes software body and various device drivers. The main part of the software realizes rasterization, and the image file is sent to the corresponding external device for output by a specific device driver. Hardware Rip is generally not flexible enough. The dispatching machine can only be used for dispatching and can not be used for other purposes. Moreover, once the main engine has problems, it is difficult to maintain; The software Rip is flexible, and the hair setter can be used for other purposes. When there is a problem with the host, replace the host and reinstall the RIP software. So the software Rip is more convenient to use. Now there are two kinds of rip in the market: one is the pspnt rip series of PKU founder; The other is the express rip series of harlequin. Founder pspnt Rip is very convenient for printing PS files generated by Feiteng or wits. In particular, PS files are generated at a very fast speed. As long as the picture path is taken during printing, the printing can be completed smoothly. However, the points it generates are sometimes false and not real enough; Printing PS files generated on Macs is very cumbersome. Sometimes, you can't print at all. In addition, in the lower version, color preview is not available for files printed on Macs. This problem was not solved until the latest founder century Rip was launched. However, the lattice information during preview cannot be stored. The points generated by Harlequin's express rip are much more tangible and clear. Whether it is a Macintosh or a PC, the layout files on it can be typeset and printed directly without the intermediate step of generating PS files. Of course, it cannot print PS files generated by wits or Feiteng. Of course, there are many difficulties in output layout:

① the problem of hollowing out the black version. After the black version is hollowed out, the black text is not directly pressed on the background color, and white appears around the text strokes. As the text is reflected on each color plate and the temperature change in the printing workshop, the paper will stretch, making the overprint inaccurate and affecting the printing effect. In order to avoid this phenomenon, you should select no hollowing out or black plate embossing in the corresponding options during hair arrangement

therefore, the temperature of the working environment of the experimental machine must be kept constant ② the consequence of changing from RGB mode to CMYK mode is that only the black version or the four color versions have the equivalent gray-scale image on the color separation chip, rather than the required color image. Therefore, you must check whether the image in the layout is in CMYK mode before publishing. In addition, it should be noted that after the image is processed in Photoshop and the layers are merged, the channel must be deleted. Otherwise, the image information will be missing during the transmission

③ the problem of bold font appears in freehand and PageMaker. If heavy is used for the Chinese font in freehand, it will cause paste when the film is released in most cases; If bold is used for Chinese in PM, it must be an overlapping word with teeth. Similarly, other font effects in PM will also have problems. To avoid the above problems, the first thing is to try to use the corresponding bold text, such as the bold song or big black. If there is no corresponding bold font, fill and stroke can be used in freehand. However, there is an experience that the size of the original font size cannot be exceeded by more than 3%. If the font itself is bold, the proportion is even smaller

④ there is gray during black overprint. If there is gray during overprint, the objects under the gray will penetrate. You should also pay attention to other specified overprint in the file, because the current version of the software can not see which objects have been overprinted. The solution to this problem is to add 1% yellow when defining gray

⑤ the result of misuse of JPEG compression format is that there are images on the screen and there are no images after output. The solution is to re store in Photoshop as TIFF or EPS format

⑥ scaling of graphs at present, it is very convenient for typesetting software to scale graphs, but the cost is multiple output time. So be sure to set the size and resolution in the image processing software, and then put them into the typesetting software

⑦ misusing DCS format will lead to three different consequences. First, the black-and-white printout has a picture, but there is no picture on the output film; Second, when printing in color, the printed color picture becomes a black-and-white picture; Third, although the printing is color, it is very rough. The reason for phenomenon 1 is that there is only a master file but no color separation file when outputting; The second reason is that the main file only contains the gray-scale image of low solution force; The third is that the main file only contains the color map of low solution force. Therefore, do not use DCS format unless there is a particularly good reason or a particularly good understanding of DCS

⑧ when EPS tape is misused, the result is that some pictures on the film are wrong when it is output on a certain line. The reason for this problem is that when the image is saved in EPS format, band plus information is selected. Therefore, do not move this option when saving EPS. Of course, EPS tape function can achieve some special effects, such as line effect or deliberately using different lines in the same layout to achieve special purposes

⑨ misuse the "pattern pattern" filling tool freehand has a pattern filling function, which can fill regular patterns within a certain range of graphics. This kind of pattern is dot matrix. The level I rip imagesetter equipped in the early stage does not support this filling output, while the level II imagesetter can output. But one thing to note is that you can't set a color other than the actual color for it. If you try to set a color of m30% and y30%, although it is displayed on the screen, the output must be 100% bright red of M and y

⑩ problems with fonts sometimes the typesetter lacks fonts, resulting in fewer words on the output film. This requires that the design and production should be prepared first to turn the text into a curve or path. If the text has special effects, the effect should be made first, and then it should be turned into a curve or path. When inputting words, you should also pay attention to using GB input method and Chinese characters with GB internal code as much as possible. And numbers

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