Problems to note before exporting

One. Scan separation

The scanner calibration principle is to adjust the scanner to be able to faithfully copy the original's tone level information, color change, and gray balance. The specific method is to use a dedicated emission or transmission color scale to adjust the gamma values ​​of the highlights, shadows, and intermediate values ​​in the scanning software. Adjust RGB or CMYK single-channel values ​​as necessary to make the electronic image's tone, color, gray balance, and color scale consistent. The steps are as follows:

1. After the scanner is turned on for more than ten minutes, the standard color mark is placed in the scanning area, and the scanning software is started to scan with the default parameters.

2. After the scan is complete, measure the grayscale color data with a probe in Photoshop. According to needs, the highlight value and the dark tone value are adjusted in the scanning software so that the first level of the gray scale is between 250 and 255 and the dark level is between 0 and 5 in the 22nd level. If the value of the dark tone after the scan is large, it means that the dark tone is not black enough. You can increase the value of the shadow tone from 0 to a larger value to ensure that the 22nd level value is comparable to 5 or less. Of course, the calibration of the white field is also the same. Between the 19th and the 22nd level, the values ​​are not much different, roughly 10 or so, the dark tone level has not been opened, and the tone is compressed and lost. This is determined by the performance of the scanner itself and has little effect on most manuscripts. For originals with rich dark shadow levels, scanning with a roller scanner is recommended.

3. Adjust the midtone gamma so that the gray level 11 is around 125. If the 11th level is too small, increase the gamma; otherwise, decrease the gamma.

4. According to the relationship between the RGB values ​​of each level of gray scale, adjust the values ​​of the three channels so that the value of each scale in the three channels is approximately equal. If R=G=125, B=119, then the gamma value of B channel can be increased to make it not yellowish. The scanned RGB image must be converted to CMYK before it can be output. During this time, the image was also color-coded and corrected.

Second, graphics, image processing and group edition

1. Setting of color separation parameters This mainly includes printing ink settings and separation settings.

(1) Setting of printing ink

1 If coated paper is used for printing, the ink may be TOYO INKS or SWOP INKS. Other parameters can be based on specific paper.
2 dot gain refers to the expansion of outlets at 50% of the midtones. If printing on coated paper, it is recommended to take between 12% and 15%; if printing on offset paper, use 15% to 20%; if printing on newsprint, it is 20% to 25%. 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 at the time of printing. This value is available for every printing factory.
4 Grayscale images use dot gain. By clicking this item, the grayscale image will change based on the dot gain compensation. The larger the dot gain value, the darker the display. The give option will also affect the conversion data of other modes to grayscale mode. For example, when you convert a grayscale image from RGB, select this item and the software will automatically invoke the dot gain value to compensate the grayscale value. The larger the dot gain value, the smaller the gray scale data.

(2) Separation settings Select the separation set up option under file/preference.

1 Separation Types There are two types of separations, GCR and UCR. You can choose one at a time. GCR is a gray component replacement; UCR is a background color removal. The background color removal here is different from the background color removal on the previous electric extension, so it is recommended to use the GCR mode.

2 determine the black version of the tone curve (black generation) when the gray content of the image is not very much (such as landscape pictures, portraits, etc.), usually set the black version of the tone of the black version; if the image is high saturation, High-contrast art photography can be used as a black version with a short tone and high contrast; when there are many gray components in the image (such as old paintings), the long version of the black version is used.

3 black limit The different types of manuscripts should have different values, from 70% to 90%, usually 85%.

(4) The total ink limit (tital ink limit) indicates the maximum value of the sum of four color dots. Such as coated paper offset printing, take 340% to 380%; newsprint is about 260%.

5 UCA Amount This value mainly increases the value of CMY at the dark tone. This value can be larger for dark manuscripts, such as 40%; otherwise, the smaller the better.

2. Color correction

Photoshop scans the output of the picture mainly from two aspects of processing: the full-color correction and selective teaching is. For full-color correction, the curves can be used to correct high and dark tone values, taking into account the tone and gray balance of the image; for selective color correction, the local color blocks in the figure can be adjusted as necessary. The amount of adjustment can not be too large, otherwise it is easy to produce hierarchical faults. After the graphic image is processed, the groupware can be used to create a version. After the group version, the output can be output, that is, the film can be prepared.

Three output distribution

The output is based on RIP technology. That is, a raster image processor, which can convert graphics, images, and text information into a variety of large-format printers or pages of the language of the machine to understand the ability to complete the output. It can control the printing accuracy, color and format size. No matter what kind of RIP, there are two kinds of technologies for converting electronic documents into print languages: First, color separation; second, screening. Separation is generally four-color, and sometimes there are more spot colors. RIP is divided into hardware and software. The hardware RIP is built into the printer imagesetter or a dedicated hardware RIP chassis; the software RIP includes the software body and various device drivers. The software body is rasterized, and the formed image file is sent to a corresponding external device for output by a specific device driver. Hardware RIP is generally not flexible enough. The issuing machine can only dispatch, it can not be used, and once the host has a problem, it is not good to repair; while the software RIP is flexible, the issuing machine can be used. When the host computer has a problem, you can reinstall the RIP software by changing the host. So software RIP is more convenient to use. There are two types of RIPs on the market today: one is the PSPNT RIP series from Peking University, and the other is Harlequin's Express RIP series. Founder's PSPNT RIP is very convenient when printing Fenton or wits-generated PS files. Special PS file generation, very fast. As long as you take the picture path while printing, you can print successfully. But the dots it generates are sometimes false, not real enough; printing is very troublesome when generating PS files on a Mac. Sometimes it is impossible to print at all. In the lower version, color preview is not available for files printed on Mac. Until the latest Founder Century RIP was launched, this problem was solved. But when previewing dot-matrix information, it cannot be stored. The Harlequin Express RIP generates outlets that are relatively solid and clear. Whether it is a Mac or a PC, the layout files on it can be printed out in a row, and can be printed directly, without the need to generate an intermediate point in the PS file. Of course, it cannot print wits or fly-through generated PS files. Of course, there are many difficulties in outputting the output:

1 Problems with black prints After black prints were blacked out, the black text did not directly press against the background, and white text appeared around the text strokes. Because the text is reflected on each color plate, plus the change in the temperature of the printing shop, the paper will expand and contract, making overprinting inaccurate and affecting the printing effect. In order to avoid this phenomenon, when publishing, you should choose not to empty or black imprint in the corresponding options.

The consequence of converting the 2RGB mode to the CMYK mode is that there are only grayscale maps on the color separation sheet that have the equivalent of the map or the 4 color versions, rather than the desired color map. So be sure to check before posting that the image in the layout is in CMYK mode. In addition, we must also pay attention to, in Photoshop in the map processing, and merge the layers, be sure to delete the channel. Otherwise, image information will be missing when publishing.

3 Bold Font Problems This problem appears in Freehand and Pagemaker. If Freehand's Chinese font uses heavy, most cases will produce a paste word when a film is produced; while in PM Chinese uses bold, it must be a toothed overlap word. There are also problems with other font effects in PM. To avoid the above problems, the first step is to use the text in the corresponding bold text. For example, choose bold song or big black. If there is no corresponding bold typeface, you can use fill and stroke in Freehand. However, there is an experience that the size of the word can not exceed 3% of the original size. If the font itself is thick, the proportion is even smaller.

4 If there is a gray net when overprinting, if there is a gray net during overprinting, objects under the gray net will pass through. Others should also note that overprinting is specified in the file because the current version of the software does not see which objects were overprinted. The solution to this problem is to add 1% yellow when defining grey.

The consequence of the misuse of the 5JPEG compression format is that there is an image on the screen and the output is missing. The solution is to save it back to TIFF or EPS format in Photoshop.

Scaling Problems in Figure 6 Now that the layout software zoom map is convenient, the cost is multiple output times. Therefore, be sure to set the size and resolution in the image processing software and then put it into the layout software.

7 Wrong use of DCS format This will produce three different consequences. First, there are plans for black and white printouts, but there are no plans for the output of the film; second, when the color is printed, the color image is changed to a black and white image. Third, although the print is a color image, it is very rough. The reason for the occurrence of phenomenon 1 is that there is only the main document at the time of output, but there is no separation document; secondly, the main document only contains the grayscale image of the low solution force; and the main document only contains the color image of the low solution force. Therefore, do not use the DCS format unless you have a particularly good reason or have a particularly good understanding of DCS.

8 Misuse of the EPS with the network is the result of a network cable output, the number of pictures on the film is wrong. The reason for this problem is that when the image is stored in the EPS format, the screening information is selected. Therefore don't feel free to move this option when saving EPS. Of course, the EPS band network function can achieve some special effects, such as line network effect or intentionally using different network lines in the same plane to achieve a special purpose.

9 Wrong use of "pattern" pattern filling tool Freehand has a pattern filling function that can fill a regular pattern within a pattern. Such patterns are dot-matrix. Earlier equipped level I RIP imagesetters do not support this filled output, and level II imagers can output. But one thing to note is that you can't set a color other than the field. If you try to set a color of M30% and Y30%, although they are all displayed on the screen, the output must be 100% large red for M and Y.

10 Problems with fonts Sometimes fonts are missing on the machine, resulting in fewer characters on the film. This requires the preparation of the design and production first, turning the text into a curve or path. If the text has special effects, it should be effected before it is turned into a curve or path. When inputting words, please also pay attention to using GB input method and Chinese characters in GB inner code. The numbers and English characters are in English. When the software has text left-right alignment, try not to use spaces to move words. If you must use spaces, use English spaces. Be careful with punctuation. Chinese simplified punctuation is below the character. Traditional Chinese punctuation is in the middle of the character.

Source: Beijing Printer Forum