Is there no need for color separation technology?
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At present, many CMYK files received by printing companies, if they directly print the plates for printing, the printed results will not follow the color drafts from the customers, or the color and level of the pictures are not good. The biggest reason is that the customers come to the files. "Separation" is not handled properly. There are two common examples. One is that the total ink volume of the CMYK file is too large, because some software sets the total ink volume in the color of 400%, and there is excessive ink in the same position during printing, which causes the ink to dry too slowly. There is a phenomenon of over-bottoming and dragging. On the uncoated paper (uncoater paper) commonly known as book paper, because the ink is too thick, not only difficult to dry, but also lead to deep dot paste together, the level is unclear. The second example is that the designer relies on the effect printed by the printer in the production process. When the print is dark and color cast, they have to modify the file until a satisfactory color is printed, but the CMYK value of the file is fundamental. Not suitable for printing. The example I have seen is that the value of a position in the file is 8%, but the color position of the color paper provided by the customer is 24% shaded at the same position. If the friend who knows the printing will realize that the 8% dot is too small, How can I print 24% shades in normal printing?
The above situation has revolutionized the prepress technology along the desktop top publishing revolution initiated by the Apple Macintosh desktop computer in 1985. The previous prepress processes included art design, image processing, and typesetting. And color separation can be done in a desktop computer. The process of the past professional is made simple by computer and software operation, so many professional jobs fall into the hands of non-professionals. Designers must have multiple roles, and must know how to type, image and color. Work, but do they have enough expertise? In addition, the industry of wording and color separation has gradually been eliminated!
In the course of teaching color management and related courses, the author asked what "separation" is. Most of the students said that they did not know. When asking this question among friends in the printing industry, many people think that the work of "separation" is no longer Re-exist. Friends who have been involved in the past few years have no idea of the "separation" work. For some time in the industry, they think that without the film and film of photography, they will no longer need the "separation" work.
In many people's minds, "separation" is to attach the manuscript to the glass cylinder of the electronic color separation machine. After scanning the original and color separation, the four-color film with the dots is directly output, which is called "separation." The implementation of the "separation" has been different, the original 掹 is attached to the glass of the scanner, through the scanner's photomultiplier tube (PMT-Photo-Multiplier Tube) or charge coupled device (CCD-Charge) -Coupled Device) Converts the color and light and dark information on the original into an electronic message, which becomes the pixel of the image (Pixel), which is called "Scanning". The scanned RGB image is converted to a CMYK image by ICC profile or color setting. This process is called "Color separation".
The CMYK file will be output to the film or plate. This is called "Output". Therefore, the three processes of "Scan", "Separation" and "Output" add up to the definition of the past "separation". .
Because of the popularity of desktop computers and software, many people can easily complete the "separation", but what is the setting behind the process of converting RGB to CMYK, most people say they don't know, then the CMYK files are separated. Whether it is suitable for the actual printing conditions is not known.
To understand the role of color separation, we begin with the principle of color reproduction. In the traditional film photography color transparent film is the use of RGB color filter, the image is recorded separately on the CMY three-layer color film, the CMY three-layer color on the color film is the principle of subtractive color to form different colors.
The transparent film is affixed on the glass of the scanner to scan the RGB image information, and the RGB value is converted into an RGB working color space, such as AdobeRGB or sRGB, by Scanner ICC profile or scan color setting. In digital photography, the image is taken by the RGB CCD, and then converted into the RGB working color space by the ICC profile of the digital camera. Generally, the small digital camera uses sRGB, while the professional digital camera uses AdobeRGB.
When the image is stored in RGB mode, it can be converted to CMYK mode by appropriate software. The most popular software is Adobe PhotoShop, in addition to other software such as Binuscan CMYK Production+ and Photo Retouch Pro, Aurelon ICISS, Alwan The company's CMYK Optimizer and most of the color conversion functions in the output RIP.
Despite the help of color separation software, operators must also understand printing and color separation techniques, such as standard print density, dot gain, overlay ratio, print contrast; color separation such as color correction, Gray balance, tonal range, color relative image, black plate generation, GCR, UCR and total ink volume, etc., can understand the function of using software, separate good image files, and print the ideal color effect.
In 1976, the author entered the three-year part of the Kwun Tong Institute of Technology to give a fake photo-engraving course. The traditional color separation plate-making technique was studied. From the lens color filter color separation, horizontal screen machine online, direct amplification machine direct color separation and other technologies, to the last year to learn to operate the electronic color separation machine. At that time, the apprenticeship of color separation technology took 3 to 5 years to complete the division. There is no "separation" project in the current design and printing courses. There is no apprentice training in the "separation" industry. I believe that the technology of color separation will gradually be lost. Therefore, the education sector should set up appropriate color separation courses. And the industry should also retain the position of color separation technician.