The hottest thing is all in color

2022-08-22
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Everything is in color

everything seems to be ideal: the customer's data has been put into production as scheduled, all pages have been completed, and the selected fonts are not missing - in short, the task has been completed very satisfactorily. But after printing, I suddenly realized that the effect was very different. The color of the original was much brighter. Even when I checked it on the screen, everything I saw was much better than what I printed

experts believe that "color management" can avoid these problems. But what is the real meaning of this term? In short, color management includes controlling the accurate, stable and consistent reproduction of colors, and the results can be predicted. The purpose is to make the final product as close to the original as possible. This topic may be a cliche for some people, but it is one of the most popular topics in some professional seminars, industry symposiums and lectures, that is, because of the content of this topic and its continuous uncertainty

in publications, a color image usually needs to go through a series of digital workflow. In addition to the host, this workflow starts with the scanner or digital camera capturing the image, reproducing the image on the display screen, proofing by the digital proofing equipment, and finally preparing for the actual printing. Generally, nothing will happen in this process, but one thing to note: color will not be easily captured, and it is more difficult to be accurately controlled

color is not a simple physical phenomenon, but a complex visual feeling affected by light, including the reflection property of the light-irradiated surface and slightly different psychological factors that affect everyone's color feeling. It is wrong to think that the rainbow contains all colors. Because color is not a single plane entity, far from assigning a wavelength to each color. In fact, we can't see the real color at all. Color is only the result of the synthesis of signals received by the pyramidal cells on our optic membrane in the brain

some systems have been tried to describe color. Usually, the color space we mentioned is some multi-dimensional coordinate systems, such as the widely used CIE color coordinate system, which uses three coordinate axes: red green, yellow blue and black white. However, no color space defined by any manufacturer can simply correspond to the color space defined by another manufacturer

different devices reproduce colors in different ways, and even cannot record and describe the same color in the same way. For example, scanners and display screens use color space to integrate red, green and blue primary colors to reproduce various tones; On the other hand, proofing machine and printing machine integrate CMYK color space to establish color. A typical prepress system can include a group of different equipment from different manufacturers, making the color management process more complicated

in previous years, the typical prepress part more or less adopted a self-contained equipment system, and its various parts can work closely to ensure complete adaptability. But now the digital equipment used in prepress operating system is mostly manufactured by different manufacturers, which also brings problems to color management. At present, it is often found that some prepress commercial equipment produced by different manufacturers form production lines, such as: using the scanners of Heidelberg, Kodak or itek, or using the digital cameras of Epson, Ricoh and Nikon for input, or directly using the images generated by customers with various software and hardware

problems caused by improper matching

when converting from one color space to another in the workflow, the problem of color management will be more serious. For example, the scanner uses RGB mode for input scanning, but what problems are abnormal with CM electronic tensile testing machine, and how to prevent the error of the testing machine from YK mode for output. Such things happen every day in the printing factory

although different devices use different color spaces and have certain coverage areas, it is still difficult to match completely. Even if two devices also use RGB color space, the results are very different. Paper and other substrates also affect the reproduction of color. These factors must also be taken into account in color management

the task of color management

the purpose of color management is to compensate for the color distortion caused by the input and output devices, ensure that the color data can be converted in a repeatable way, meet professional requirements, and finally establish a color expressiveness that does not vary from device to device. This is mainly achieved by the method of "equipment color calibration"

theoretically, color profiles should be based on widely accepted standards. The International Color Consortium has developed such a color space standard ICC profile and the necessary color management module for the modular software and hardware environment. It uses these standard files to convert colors into a color space that is not affected by devices when they are input or output

Apple Computer's MacOS operating system fully supports colorsync color management system. Colorsync is based on the technology developed by Linotype hell company (now Hyderabad prepress) and handles color conversion. This colorsync software will coordinate among the operating system, applications, ICC profile and CMM, and can even convert between different module systems using different color conversion methods. With the permission of Heidelberg prepress department, Microsoft used ICM technology in Windows operating system

the truth of color management

when an image is scanned or captured with a digital camera, the results must be viewed on the display screen. Here is the first pass. Both these two devices need to be calibrated and the correction curve should be calculated to make up for the difference. To calibrate the input device, a reference document is required. Usually, a color slide is used, but so far, with a color block test strip. This test strip should be consistent with the it8 standard used for all device color description documents. You can use a spectrophotometer to measure the original, of course, you can also use the measured color value document to omit this step. The second step is to measure an actual scanned image with a spectrophotometer, compare the result with the previously stored reference data, and establish a set of difference values. This is the profile supported by the corresponding software, which can be used to convert the scanning data into a color space that does not vary with the device, and also use the same method to calibrate the display screen, proofing machine and the final output device

the printer introduces uncertainties

naturally, the final output print is the final test of color management. Standard color control strips have been designed as the color calibration of printing machines. Such differences are not simply reflected in products and technology. The color reproduction quality of printed matter can be tested on printing sheets. However, due to the inherent limitations of the offset printing process itself and the need to maintain a balance of a large number of variable factors, a considerable amount of instability is added to this process, and profile can only calibrate a device under specific data settings, so it is very important to keep the printing conditions unchanged. Ink, ink bucket settings, paper and even temperature and humidity will affect the quality of prints

prospects

in fact, due to the weaknesses in the process, various devices need different profiles and processing schemes, and color management cannot often achieve the desired effect. As long as one link in the production process is improperly calibrated, or the wrong or outdated profile is used, the whole process flow will be destroyed. Manufacturers are also aware of these problems and have begun to propose efficient color management solutions, including powerful calibration tools designed for many devices

in fact, color management technology has not been widely used. Some people hesitate because of this complex thing. Many tools and systems on the market not only fail to help potential users find out the direction, but also make them more confused. Moreover, many statements about "color management" are swaying at will. Various statements only talk about some aspects narrowly, rather than describing this technology as a whole. Moreover, in essence, the fundamental problem of color is entirely a subjective phenomenon, which makes it difficult to control

however, in any case, the day when color management can be used to ensure the faithful reproduction of high-quality printing colors is not far away. In fact, as this article explains, there is an urgent need to advance color management

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