The ideal and reality of the hottest color managem

Ideal and reality of color management

color reproduction is an important task of plate making and printing. For a long time, the color inconsistency between the original, display, proofing, printing and other links has caused great confusion to users. The color that users see on the screen is completely different after printing, or the color of the printed finished product is inconsistent with that of the signed sample, causing unnecessary disputes between merchants and customers. This situation puzzled the industry for many years until the proposal of color management, which made people see the hope of changing this situation

there are many kinds of color devices, such as scanners, digital cameras, monitors, printers, printers, etc. different types of devices, even the same type of devices with different models, have different color performance capabilities. For example, different scanners scan the same original with different results, and different displays display different effects on the same image, not to mention the color difference of printed products caused by different ink and paper. The fundamental reason for this difference is that each device represents color in its own color space. In other words, the definition of color is related to the device, such as defining the RGB value of a color, It is suitable for a certain display of users. When the same value is transferred to another display, the color effect obtained may produce a production volume of more than 70million tons/year. The reason is that when a color is transferred from one device to another, the conversion between color spaces does not match well

the mode of color management is: from the color in a device color space, combined with the feature file of the device, it is converted to the intermediary color space, and then combined with the feature file of the target device, and then converted to the target device color space. In this process, due to the use of device independent color space as an intermediary, so as to ensure the consistency of color

from this, we can summarize three elements of color management:

(1) there must be a device independent color space as an intermediary for color conversion between different devices

(2) there must be a standard specification for each device to describe its color characteristics and parameters

(3) there must be an accurate conversion algorithm to realize the conversion of colors between different spaces

in order to standardize the standard of color management, Jinan new era Gold Testing Instrument Co., Ltd. has been producing experimental machines for so many years, the international cocor consortium has formulated the ICC specification, which is supported by the majority of manufacturers today. ICC specification is the result of negotiation among many manufacturers, which is independent of equipment and platform. It describes the method of mutual conversion between equipment color space and intermediary color space

the formulation of ICC specification is an element of color management, which has been clarified

(1) the color space as an intermediary is CIE XYZ or CIE lab

(2) the file format describing the color characteristics of the equipment is the format specified by ICC. For CMYK type devices, multidimensional lookup tables are usually stored in ICC files; For RGB type devices, ICC documents usually store the algorithm of mutual conversion between RGB and CIE lab

(3) the color matching algorithm is completed by the manufacturer according to ICC specifications

take an example of digital proofing. Let's see how color management works. There is a color value (CMYK) suitable for printing. According to the ICC characteristic file of the printing environment, we can calculate the visual chromaticity value (CIE LAB) after printing. Now, according to the ICC characteristic file of the color printer, we can calculate another group of (CMYK) colors required by this (CIE LAB) color. This group of (CMYK) values is certainly different from the original (CMYK) values, but after being output by this color printer, You will get the same visual effect as printing, that is, the same (CIE LAB) chromaticity value

the implementation of color management requires a stable color environment. If digital proofing is required and automatic data saving, processing, printing and dynamic playback of experimental process can be realized, the result is consistent with the printing result, then the surface quality of modified polypropylene material must be improved before, and the printing environment must be stable, which is not well done by some units with lax quality control. If the display, proofing and printing are required to be consistent with the original, the premise is that the quality of the original must be guaranteed. Foreign countries strictly abide by the principle of color reproduction. If the quality of finished products is not high due to poor originals, the plate makers do not have it, and the customers will not be held accountable. This is difficult in China, because the quality of the originals is uneven. Customers' requirements for plate makers are not to be faithful to the reproduction of the originals, but to improve the quality of the originals to a higher level. Under such realistic conditions, the implementation of the so-called whole process color management will not achieve the desired effect. Some domestic manufacturers have been aware of this problem. They are accumulating and analyzing the characteristics of domestic originals, hoping to classify domestic originals and summarize the scanning and color separation parameters of each type of originals. On this premise, it is meaningful to implement the whole process color management. (end)