Analysis of High-fidelity Print Color Space II

2.gcr (full replacement of gray components)

The so-called gcr is to replace the gray component contained in each version of cmy with a black version. In the four-color printing, gray is represented by the intermixing of the cmy, and the gcr is expressed by completely replacing the gray component with the black ink, and the corresponding portion is removed from the cmy plate. By using this method, the black ink is not only used. It is a tertiary color that is related to a gray component, etc. To express the luminance gradation of the primary color and the secondary color, the gray balance of the turbidity and the gray-scale region generated due to the color intermixing is not degraded, and stable color reproduction is achieved.

The four-color printing press prints the second color and the third color on the ink of the first color, wet and wet, but the gcr, as shown in FIG. 3, reduces the total ink volume and eliminates the ink overprint to obtain a stable color. Color reproduction. At the same time, it can also reduce the amount of ink. When using gcr, when there are many dark shadows in the image, if the gcr is used excessively, it will produce a density lower than the usual 4-color performance, and the phenomenon of tone reversal will occur in the dark tone. Therefore, the printing conditions must be fully considered before the work. , pre-tested to set.

3. FM screening (mf screening)

The problem when using am screening is how to set the angle in the respective separation. The dot points assigned to each color are within 90 degrees (3x30 degrees). In the four-color printing, the c, m, and k plates are arranged at an interval of 30 degrees, and the y printing plate with the highest brightness is used at an interval of 15 degrees.

Fifth, high-fidelity printing with color proofing

Can not reproduce the high-fidelity printing directly with the proofer, but the use of Heidelberg's coloropen software, made of icc outline map, can be four-color image data directly with seven-color images on the monitor screen and proofer output. The monitor screen is composed of rgb light emitting elements and has a wider color space than prints printed with four color inks, and is not a problem for high fidelity print reproduction. The difference in the production of high-fidelity printing ICC contour map is that it will create a 4-color contour map color table, using the edermcs software first by 5-8 color separation, the 8-color printing press to print color table (test form). The printopen is then entered after measurement with a spectrophotometer to create a high-fidelity print profile.

For image correction software, as long as the icc contour image for high fidelity is installed, the image data can be directly processed with 4 colors of cmyk, and 5 or 8 colors are displayed on the monitor screen as usual, and color correction is performed. When the proofer is used to output the proofs in page units, the icc contour diagram for high-fidelity printing is not limited to the four-color image data. Therefore, all the images and peace nets (equal dot patterns) and hierarchies become high-fidelity print performances. problem. It can be seen that the only printing machine proofing is the proofing method of the final printed matter, so a printer with a reliable quality management device is needed.

Six, automatic adjustment of ink volume

For quality management of prints using spot ink, a quality management device such as a Heidelberg image manager of a spectrophotometer must be installed for measurement and management. In actual operations, for high-fidelity printing, the cmy and rgb editions are entered as the standard values ​​for the ink data of the edermcs, in addition to the k edition, and applied to quality management. As for the quality management device, the spectrophotometer is used to accurately measure the color patches on the control strip, and the numerical value is determined by the lab value. In the case of a densitometer, the thickness of the ink film can be measured, but the difference in the color cannot be measured correctly. If a spectrophotometer is used, the color is represented by the lab value. For special colors used in high-fidelity printing, the printer can be continuously printed under the same conditions at all times.

When using ctp to directly output the plate, digital data can be output by rip. As long as the cip3 data is produced at the same time, the printing process time can be shortened. The cip3 data is transferred to Heidelberg's prepress interface. After being converted into the ink fountain data of the printer, it is then delivered to the cp2000 connected to the printing press. The amount of ink supplied to the printer is automatically set. The best ink density can be obtained without hands.

The printing sequence when using an 8-color printing press is k, c, m, r, air, g, bv, y in accordance with the seven colors. In principle, the ink with high transparency should not be smeared mechanically and then refined. . The main point is that the ink cartridge must not be mixed with other colors, and it should not be used as an 'empty', and it is necessary to move y as the final printing cylinder, which can improve overprinting and color reproducibility.

Seventh, printing automatic registration

High-fidelity printing of more than 5 colors, for the printing register set the rules of the line, due to the increase in the number of colors to bring the rules line superimposed, so to identify their own rules line is very difficult. If there is a rule line misalignment at ordinary times, it is possible to identify all the colors by means of a magnifying glass, and if it is superimposition, it is difficult to recognize using a 25 times magnifying glass. If you are using manual work to register, you can easily register by simply shortening any of the rules of the cmy or rgb version. If you use Heidelberg's automatic register system, rely on the use of special registration marks, rely on sensors to automatically identify, which can completely solve the trouble of the register operation, 7 colors or 8 colors, limit the registration to 100 Resolved within.

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