Application and Research on color management techn

2022-10-15
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Application and research of display color management technology

the application of color management technology in the printing industry is becoming more and more important. In the process of color management, the two most important links are the color matching between the original and the display, and the color matching between the display and the output of the print or printer. In these two links, the display plays a very important role in the whole process of color management. Whether the display result of the display is accurate or not will directly affect the accuracy of print output. Therefore, the color management of display is an important basis for color management

first, the principle and method of display color management

the color management technology of display is mainly divided into the calibration and characterization of display. Display calibration refers to the process of determining and adjusting the best or specific display state for a variety of performance experiments of tapes, chains, wire ropes, electric welding strips, bricks and components that generally require small inner friction coefficient and suitable outer friction coefficient. The best state refers to the neutral colorless state in which the display achieves the best brightness, contrast effect and a certain color temperature through adjustment. A specific state refers to a situation that mimics the appearance of a specific environment

the display calibration system can be divided into two types according to the use mode and principle:

1 Pure software

① usage. Such as Adobe gamma, monitorcalibrator and other software, through state observation and manual setting to achieve a certain ideal or specific working state

② working principle. Adjust the LUT table of the display card to complete the adjustment of the effect change. LUT table is the transformation table between the pixel value of the display image and the driving value of the display driving circuit

2. Software and hardware Cooperation (including colorimeter or spectrophotometer)

① use mode. Such as prifilemaker, measuretool, EyeOne and other systems, which have a target state feedback detection and adjustment structure composed of a display colorimeter. The display panel buttons of this system can adjust brightness, contrast and color temperature, and achieve a certain target state through the display data of the display interface detected by the colorimeter and the interactive adjustment of the panel buttons

② working principle. Adjust the display effect by changing the LUT table in the display card. After reaching the set target state, it is necessary to solidify the calibrated mapping table in the display card. Figure 1 is the adjustment schematic diagram of the combination of software and hardware. Its feature is that after setting a specific state, the change of calibration is obtained through the mapping method of the display card look-up table. The disadvantage of this system is that it has no direct recovery and compensation ability for the performance degradation of the display. The calibration compensation based on the display card LUT is only a mapping change under the existing display capability

after the display is calibrated, the ICC profile in the corresponding display mode can be made. This process is called characterization

II. Experiment and analysis of display color management

in this experiment, eye one match3.0 display correction software is used to manage the color of the display, and the accuracy of display correction is analyzed through the experimental data

1. Experimental equipment

Hardware: Great Wall m176 LCD, eye one Pro colorimeter

software: eye one match 3.0 display correction software, profilemaker pro5.0.5, Adobe Photoshop CS3

2. Display color management experiment

this experiment selects eye one match 3.0 correction software to manage the color of the display. Eye one match 3.0 is a software specially used for display color management

① control of experimental conditions

a. under different light source lighting conditions, the same color will have different color appearance. Therefore, it is required to be under the same light source when the display is calibrated and measured, establish a neutral gray environment and standardize the light source, turn off the surrounding strong light, and it is best to use a light shield. D65 light source is used in this experiment

b. before correcting and measuring the display effect of the display, first clean the display screen, and pay attention not to squeeze the screen when wiping; Turn on the display for at least half an hour to make its color stable; Turn off the color management function and screen saver of the monitor

② display correction steps

a. set the target of the display: set the target color temperature to 6500k; Set the target gamma value to 2.2; The brightness of the target white field is set to 120 CD/m2

b. environmental light source inspection. Whether the ambient light is appropriate will ultimately affect the success or failure of the experiment. During the experiment, the ambient light should be kept stable and no strong light should appear. The software has an automatic ambient light detection page. When the ambient light is in the appropriate state to carry forward the Guangda and Dazhong pharmaceutical industry, the black slider is in the green range

c. contrast adjustment. Adjust the contrast of the display to the maximum, place the measuring equipment in the corresponding position, and click the start button to start the contrast adjustment. In this process, we should constantly adjust the contrast of the display until we finally get a satisfactory effect, that is, let the black slider be within the green range

d. brightness adjustment. First, set the brightness value of the display to the lowest. After clicking the start button, increase the brightness value according to the software prompt until the slider is in the middle of the green range if the project succeeds in achieving the desired effect

e. adjust the R, G and B color values of the display. After selecting the white dot color temperature, put the screen calibrator in the corresponding position, and adjust the R, G, and B color values of the display until the black slider is in the middle of the green range

f. measure the color block. By measuring 42 standard color blocks of the software, the curve of the graphics card is automatically adjusted to match the target setting, so as to adjust the overall performance of the display. The software automatically locates the position of eye one, and there are constantly changing color patches. The software will compare the color information obtained by eye one with the original color information and make adjustments, as shown in Figure 2

③ display characterization

after correction, the characteristic curve of the display is obtained. The more linear the characteristic curve is, the more accurate the corrected screen is. Save the obtained ICC characteristic file to: windows system32spooldriverscolor, and apply it to the system to complete the color management of the display, as shown in Figure 3

3. Color difference analysis of display correction results

use Macbeth ColorChecker chart to accurately evaluate the accuracy of display characteristic files and analyze the effect of display color management. The Macbeth ColorChecker chart standard plate contains 24 color blocks, covering most of the colors in the color gamut, and many of them represent memory colors and neutral colors, such as skin color, plant and blue sky colors (as shown in Figure 4), which can accurately evaluate the color management effect of the display

III. experimental summary

through the experimental results, the average value of color difference generated by using eye one match 3.0 to manage the color of the display is 4.04, the maximum color difference is 7.8, and the color difference tolerance specified by the printing industry is △ eab=6. Therefore, from the perspective of objective evaluation of color difference, the color difference of the display can be accepted by the printing industry, which proves that using eye one match 3.0 color management software, using the correct experimental method, The accuracy of the produced feature file is very high, which can realize accurate color management

to do a good job in the color management of the display, we should pay attention to the following points:

① before the color management of the display, the display must be preheated for 30 minutes in advance, and the ambient light must be controlled in neutral gray

② select the correct display correction software for scientific and reasonable operation. Experiments show that eye one match 3.0 color management software can achieve accurate color management

③ adjust the display regularly. The display will gradually age over time, and the performance will decay, and the color reproduction performance of the display will change accordingly. Therefore, it is necessary to regularly compare with the proofing draft, and regularly calibrate the display with the screen calibrator. The correction items mainly include brightness, contrast, gamma value, fluorescent agent type, etc

④ manage the ICC files of the display well

⑤ keep the standard proofing draft properly, and replace it in time if there is fading; The image file of the standard sample shall be permanently saved so that it can be called out for direct use when the sample fades

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