Scanner color control technology

With the continuous development of the computer industry and the printing industry, new printing technologies and new equipment emerge in an endless stream. Direct plate making technology, digital printing technology, digital color proofing technology, and multi-color high-security printing technology have gradually been applied in production. These new technologies pose challenges to quality control processes based on human experience in traditional printing. The application of these new technologies requires that we must digitally control the consistency of printed products and achieve high efficiency.
In the current printing quality control, the most important part is the color control technology. What is commonly referred to as "what you see is what you get" in the printing process is actually to realize the true realization of color in the process of printing and copying. This depends on the “color management system” that is currently heard in the prepress industry. The so-called color management is the digital control of the scanning process, image display and processing, digital proofing process and printing process, so that the consistent color throughout the entire process. In layman's terms, from the manuscript to the proofing to the printing, the color is consistent from the human visual point of view.
According to our practical experience, the same original, scanned by different scanners, will generally show different results. In addition, an identical image, displayed on a different display, will have different color tones. A scraped page is printed on different color printers and the output is different. Similarly, the same set of printing plates, printed on different papers, such as newsprint and coated paper, or printed with different inks, such as European inks and Japanese inks, have different effects. In other words, there are several reasons for this. First, it is also a display, printer, and ink that are produced by different manufacturers. Its color characteristics are different, some reddish, some blueish. In addition, scanners and monitors all work in the RGB color space, and the printer's printers work in the CMYK color space. If we want to be able to control the correct delivery of colors in today's open systems, we must have the following conditions:
1. Be able to know the color profile of each device in the system. The documents that describe the characteristics of these devices currently use the ICC format defined by the International Color Council.
2, can control the color data. Matching correctly from one color space to another, this is called color matching in color management technology.
3, can find a color space independent of the device to correct the color.
According to the current development trend, professional prepress equipment currently on the market, such as high-end professional scanners, professional Apple COLORSYNC monitors, and professional color digital printers, all come with special ICC file formats. These documents can accurately reflect the situation of the equipment. However, in the current work, the environment is ever-changing, and the color characteristics of pre-press equipment will change due to changes in the environment. More importantly, in the current printing process, due to the use of different printing conditions, such as different paper and different inks, resulting in a complex back-end printing characteristics. How can the various changes in the back-end printing process and the pre-press process be coordinated to make the images appear more realistic on the display, and the digital proofing effect is closer to the printing effect. Major pre-press manufacturers invested in this area A lot of energy. So far, it should be said that gratifying results have been achieved. In general, the color management system is provided to the user along with the scanning equipment of various manufacturers, so in the following I will introduce the color control technology of various manufacturers in combination with the current scanning equipment of various manufacturers.
In the current market, there are desktop scanners based on A4 format with a small design room, an optical resolution of 1000 DPI, and professional roller scanners based on large-scale printing plants and plate-making magazines. However, I believe that most of the sensitive professional users of the holding device is often between the two, they are usually A3 size scan format, optical accuracy of 2000DPI or more, without distortion and amplification rate of more than 8 times, with scan positive film, negative film , ordinary print and three-dimensional items. Due to different optical principles, there is a slight gap between some high-level manuscripts and drum scanners. However, better color control software and relatively low prices make these platform-based scanners large numbers of publishers. , newspapers, small and medium-size platemaking centers, packaging and printing plants and advertising companies. In China, the representative of this product is:
(1) Heidelberg's fast-moving platform scanner, whose scanning and color control software is the famous LINOCOLOR.
(2) Israeli Saatchi EVERSMART series platform scanner.
(3) Microtek's ARTIXSCAN2020 and other products. The scanning and color control software it uses is the software COLORQUART of Danish SCANVIEW company.
(4) Color Screen scanner from Japan Screen Company. The scanning software that comes with it is COLORSCOPE PRO.
(5) Agfa's T5000 scanner, which uses a color management system coloonun e pro.
The color management soft year attached to these scanning devices supports color management based on the ICC format and is compatible with Apple's COLORSYNC color management system. However, from its kernel, it is still different.
Hyde Protection's LINOCOLOR, Saturn's color control software and SCANVIEW's COLORQUART color management software are all based on the CIELAB color space. CIELAB Color Width is based on human visual perception and accurately describes all the colors that human eyes can see in three-dimensional space. CIELAB space is device-independent and includes RGB color space and CMYK color space. Therefore, the CIELAB color space as a color management space, on the one hand, covers a larger color gamut, and on the other hand, an intuitive color correction method derived from the CIBLAB color space also brings convenience to users. In the color management system, the color matching method is the core content. Since printing is a continuously compressed copying process, the system must transform the color data from the other three-dimensional color space to the four-dimensional CMYK color space according to the actual printing conditions, which requires long-term experience and in-depth research. At this point, companies are different. Heidelberg proved to be more successful in this regard.
At the back end of the printing process, the output can be digital proofers, digital printers or out-film processing. Different types of digital proofers and different printing conditions have different characteristics. To measure these characteristics, companies have developed software that generates these color characteristics. Heidelberger's COLOR OPEN can generate print characteristics curves for displays and back-end printers and proofers. Saturn's PROFILEWIZARD and Agfa's Coltonunepro have similar functionality. If the color characteristics of the printer and the print proofer are measured, digital proofers can be used to simulate the effect of the printer in application software that supports ICC profiles for color management, enabling accurate digital proofing. In addition, since we can measure the characteristic curve of the back-end printing, we can separate the color according to the color characteristics of the back-end during color separation. In this way, the back-end printing effect and the front-end display and proofing effect can be coordinated.
In the current scanning software, each company will follow its own research on color and printing technology, along with the printing characteristics curve under different printing conditions. Under normal circumstances, these printing characteristics are generally more accurate, and users do not need to make more adjustments. Users can use these color separation curves to achieve screen software proofing on one hand, and on the other hand, they can get ideal printing results.
In general, it is easier to implement color management in a fixed system, but if the system constantly changes or the external conditions change, you must adjust it accordingly. But good scanners with color management systems do give you the benefits you see.