Data Management Method for Copying and Restoring Originals in Color Printing (1)

The purpose of the color print copy is to use the dots to restore the color of the original, that is, the print copy should be visually consistent with the original. Since the color of the manuscript (such as photographs) is represented by the density, and the color depth of the printed reproduction is represented by the percentage of dots of the ink, it is impossible for the printed copy to be completely consistent with the manuscript. The goal is to make the printed copy as close as possible to the original.

In recent years, China has imported a large number of advanced printing and copying equipment (such as color desktop platemaking system and Heidelberg four-color offset printing machine), and the printed copy has a large difference from the original. The quality of printed matter is also quite different from that of advanced countries. The main reason lies in the fact that staff often act on the basis of experience and do not organize production according to scientific methods. It is difficult to achieve the intended purpose by manipulating advanced printing and copying equipment based on experience. After nearly two years of hard work, Beijing Shangpin Plate Making Co., Ltd. put forward that "we must develop color printing as a high-tech industry to develop", "experience without theoretical basis is not a good experience," and "every step of color printing reproduction must be strictly implemented." "Data Management" and other viewpoints have made gratifying achievements. The summary of the past two years of Shang Pin Company's experience and some technical improvements made in the color printing reproduction are as follows. We hope to play a valuable role.

The color printing and copying are divided into two parts: the color printing plate making and the color printing. The color printing plate making mainly uses the color desktop plate making system. The system is generally divided into four parts: scanning, making, filming, and proofing. Each part should have a set of scientific detection methods, and empirical things without theoretical basis are not reliable. Since each unit uses different equipment, raw materials, and inspection tools, the data will be different. Only by determining the data of each unit based on theoretical and scientific detection methods can the purpose of restoration of the original document be ensured. Take Shangpin Company as an example to introduce how to determine the various test values ​​for each step.

The product company has a Klausfeld 646 electric extension. Through the high-end networking of SUN workstations, there is a PANTHER46/HS four-imagesetter, nine Apple computers, a Japanese KF-123 proofer, and others such as : Film Fixing Machine, Laser Printer, PS Plate Processor, Slab Printing Machine, and Transmission, Reflective Density Meter and other auxiliary equipment. The raw materials used are Kodak film, PS plate, DIC ink, import 157g coated paper. The company invented and produced electrical extension cleaning agent, rubber blanket recovery cleaning agent, ink cleaning agent, film detection signal strip, proofing detection signal strip, standard color Blocks and so on.

The Klausfeld electrical extension is mainly used for scanning, first of all to make it in the best working condition, to establish 16 levels of gray balance parameter values ​​and the amount of 24 standard color correction channels, to ensure that the original gray and color Faithfully restore. Second, implement the standardized calibration method, using the white and black ladders of the gray ladder rule as the calibration points for the white and black fields, using the AUTO key to set the white field to 0%, and the black field to the C version as 93%, you can restore the tone level of the original. Third, in order to detect the scanning effect and the accuracy of data transmission in the networked interface system, two Kodak gray grading scales (one reflecting ash scale and one transmitting ash scale) and one set of Kodak standard color blocks can be taken. The ruler and the standard color patch are scanned as a standard document, and the scanning result is transferred to an Apple computer. The scanned two ladders and the standard color chart are opened by Photoshop software, and each ladder or each color block is replaced by a straw tool. The detection value (CMYK) is recorded. Since the scan head of the electric extension is a densitometer, the C and M of each step and color patch are detected by the scan head aligning each step or color block of the two ladders. Y and K values ​​are recorded and compared with corresponding data detected by Photoshop softly. If the data are basically the same, it indicates that the parameters of the scanning set by the electric extension are transmitted to the Apple computer without loss of information.

Scanning is a key part of restoring originals

Scanning is the key to restoring originals. There are many platemaking centers that use platform scanners to scan and print out proofs. As a result, the level of the picture and the degree of sharpness to restore originals are all relatively poor, making it difficult for customers to accept. To make high-end print copies, we must first think of high-end network scanning with electricity extensions, or scanning with a roller scanner, in particular, there must be a scientific calibration method, otherwise it is difficult to restore the original.
Detection scan quality must be equipped with gray ladder ruler, standard color block, electrical extension scan head and Photoshop's pipette tool. The purpose is to detect whether the electrical extension machine faithfully displays the manuscript data in the computer image file, and also detect the calibration during scanning. The method is correct and provides a simple calibration method for restoring the original.

It should be noted when using Apple Computer

When using Apple Computer, you should pay attention to: The pictures scanned by the extension can only be repaired dirty, cropped, try not to adjust the picture level, clarity, contrast, etc., do not zoom in, zoom out, should try to solve these problems when the extension scan problem. The picture format must be CMYK format. If there are major defects in the original, it can be adjusted as appropriate by the customer. This is a task that cannot be accomplished by the traditional version mechanism. Shangpin Company mainly uses software such as Photoshop, FreeHand, Quark, PageMaker, etc. It mainly uses Hanyi fonts and Founder fonts. Computer production can be combined with text and pictures, and make inkjet proofing for customers to proofread, before leaving the film must also be a laser sample for customers to compare. The tools used to detect the quality of production include color ink jet printers, screen corrections, laser printers, and standard color blocks printed at standard densities using the fixed ink paper used by the company. The purpose is to prevent unnecessary errors when publishing, so as not to waste film.

Filming is the most problematic process

Filming is a process that is most likely to cause problems, but it will never change, as long as the percentage of dots in the image is faithfully shown on the film. To this end, our company has designed a set of signal strips that detect the quality of the sheet, as follows:

The color of each color block is filled in with the data below the block: C:x% M:x% Y:x% K:x% (x indicates the data under the block). Make a PageMaker file, normalize the PageMaker file, develop, fix, and measure the percentage data of each block with a transmission densitometer. If the difference between the upper and lower points of the set data does not exceed 2, then the photosetter and the developer adjust It is very consistent, otherwise it will be necessary to readjust the redistribution data of the imagesetter. Shangpin Company stipulates that every time a roll of film is replaced, every time the developing machine is cleaned, it must be detected once with the signal bar, and the formal hair piece can be made only after meeting the standard requirements. Fortunately, each version of the software has a signal strip after it has been sent. If you don't feel comfortable, you can also check the signal strips around the scanned film.

The quality of the film directly affects the effect of printing and proofing

The quality of the film directly influences the effect of printing and proofing. One must ensure that the percentage of the outlets of the film is accurate, and the other is to ensure that the density of the film at 100% is within a suitable range. The product of the product will be 100% of the film. The density value is set between 3.8 and 4.5. Why is this specified? If the percentage of outlets displayed on the computer is 50%, the percentage of film outlets only reaches 45% or reaches 55% after being output by the photo-composing machine. This indicates that there is a problem with the photo-composing machine, which will inevitably result in a reduction or increase in the number of proofing outlets. The purpose failed.

The requirements for proofing are: 3% of outlets are not lost, 95% of outlets are not pasted, PS version is not dirty, and these three points are contradictory. At 100%, the density of the film is too high. It is easy to paste about 95% of the dots in the image. The image shows a dark mole. Just like a person's hair can not see the hair, but can only see a dark one. If the density is too low at 100%, it is easy to lose 10% or less of the dots in the print. Some people may say that when the density of the 100% external film is too low, the exposure time of the PS plate will be reduced, and 3% of the dots will not be lost. But at this time, the PS version will definitely appear floating. Therefore, according to the PS version used, the exposure time of the printing machine, and the fixing condition, the density value at an optimum 100% dot is adjusted.

The photosetter has a fast hairpiece and the percentage of outlets is controlled very accurately; while the electric extension has a slower development rate, the percentage of outlets can only control a few points, but the shape of outlets looks good. Shangpin Company rarely uses electric extensions for hairpieces. The main reason is that the percentage control of outlets of electric extensions is not very accurate. Although the shape of outlets is not very good, as long as the right PPD is selected, the generation of moire can be avoided.
Tools for detecting sheet quality include: transmission densitometers, self-made signal strips, and signal strips after various types of publishing software are taken out. The purpose is to detect whether the percentage of outlets set in the computer file is faithfully displayed on the outgoing film, and whether the density at 100% of the printed film meets the requirements for proofing.