Device-independent color spaces are mainly used for color modules and for conversion between RGB and CMYK modules beside the system.
Each color monitor has its own color gamut due to different RGB phosphors even if it is manufactured by the same manufacturer in the same year Limitation, because the colors generated by the two different formats of RGB and CMYK will vary from device to device, which is the characteristic of the color space to which the device belongs.
Some color spaces allow colors to be expressed in a device-independent manner. Color does not depend on any particular device, but a true color statement after being perceived by the human eye. These color statements are called device-independent color spaces, and were developed by the International Standards Committee (CIE) in 1931, so they are called CIE-based color spaces.
The goal of CIE is to establish a standard system for repetitive color communication for manufacturers of paints, inks, dyes and other colorants.
The most important function of these standards is to provide an overall framework for color matching. Device independent color spaces are used to convert color data from one device-specific color space to another device-specific color space. Those representing the entire visible color range are conversion spaces. , Which means any color selected on the display screen is the color gamut of the neutral color space.
CIE L * a * b * is a three-dimensional color space based on human color perception, and is the most widely used color space for CIE. L * a * b * color space is based on a color that cannot be green and red at the same time, nor at the same time. It is the theory of blue and yellow, and the result may be that a single shade can be used to describe the red / green and yellow / blue properties. The CIE L * a * b * space represents that the color is related to the reference white point. As the specific meaning of white light, it is usually based on the whitest light that a device can produce. The CIE color space constitutes an independent color basis for devices used for color management.
Although color can be reproduced in the way that comes to mind, there are only two basic methods—additive color and subtractive color, both of which are commonly known as tricolor, and are based on the different principles of the three primary colors to create full color. Understanding these two systems will enable you to understand the principles of many color reproduction jobs in printing. It is the basis for understanding the tone reproduction, gray balance, and color correction of halftone color reproduction. It is useful for obtaining appropriate contrast, color balance, and color tone. Its decisive.
Printing is based on the subtractive color method and is usually printed on white, near-white paper, or any other white object. Since the surface of the "white" paper reflects all the light waves in equal amounts, white appears. When the color is copied, we will I will intuitively think that the color is in the paper. In fact, after printing on the surface of the paper with transparent ink (cyan, magenta, yellow), the color appears after filtering out the red, green, and blue light waves through multiple combinations. Considering the transparent four-color ink, such as the red, green, and blue wavelengths that our eyes feel, rather than the combination of copying the color on paper, we found that by combining two ink color light waves and subtracting another ink color light wave.
In theory, the combination of all three-color inks can avoid all reflected light waves and produce black. Even the best four-color inks will not absorb light waves uniformly. When cyan, magenta, and yellow inks are combined, the combined three-color inks absorb The wavelength is not consistent, and the red part of the spectrum reflects more, resulting in a brownish tone instead of black. In order to make up for this shortcoming in printing, it is necessary to use black ink in the color printing process.
Paper has a significant effect on color reproductions. Paper reflects unabsorbed light waves to the viewer, and coated paper has a strong reflective surface that can produce a wider color range than uncoated paper. Rough uncoated paper The surface diffuses light and reduces the amount of reflection for the viewer, so the color is dark.
A problem that has been explored since there were color replicas before. Before the 1970s, most of the color separations were placed in front of the plate-making camera or magnifier lens with red, green, and blue filters. Skilled technicians used their own experience to obtain a good set of color reproductions. From the original manuscript through multiple procedures to make color correction film, color separation film, and screen, and then dot erosion in order to obtain the ideal halftone screen. Later, some manufacturers used the contact exposure method to change the dot size. With multiple adjustments, it takes a long time, and it may not necessarily obtain the desired color.
After the 1970s, the era of high-end electronic or laser scanners used countless knobs and buttons for color adjustment. Although these expensive analog scanners lacked computer memory and digital devices to store images, the later models used computers to convert RGB digital color signals into CMYK color separations. The originals were installed on one transparent cylinder, while the other cylinder The color separation film is installed, and the scanner is calibrated by experts trained in high-level technology to make the best input and output settings. However, rescanning is still quite common, especially for prints that pay particular attention to color. If the colors are not matched, the adjustment of the scanner or the knowledge of the operator is usually not a limiting factor, but is affected by the quality of the ink and paper.
With the addition of sophisticated color control on the scanner, from pre-press, post-press or post-press, from using the naked eye to adjusting the color control through several density meters, quality control charts, ink and paper testing, printing has been transferred from the process to Technology.
In the 1980s, advances in minicomputers, memory, and storage devices enabled color electronic prepress systems (CEPS) for storage, display, color correction, and image matching. For example, Scitex Response and Hell Chromacom and other tens of millions of yuan systems can obtain high-quality color reproductions, but they also require a long time to learn.
In the 1990s, desktop powerful electronic prepress systems appeared. Innovative page description output (PostScript), image platforms such as Apple, Microsoft, and publishing software such as Adobe Photoshop, Quark Xpress can use desktop hardware to make high-end color quality, and its easy-to-use, low-cost combination system quickly replaces Expensive stand-alone system.
Scanning and color separation, which once required highly trained experts, became popular. Anyone, including photographers, designers, typists, and computer operators, can operate a computer, scanner, and printing machine to complete color separations. Full operation. The desktop computer system uses an open system and can theoretically support various color computer peripheral devices without limitation. Today, although many such color publications can work consistently, they still have to face the same problem, how to make accurate colors.
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