The application of color management technology in the printing industry is increasingly important. In the color management process, the two most important links are the color matching between the original and the display and the color matching between the display and the print or printer output. In these two links, the monitor serves as an extremely important “bridge†in the entire color management process. The display accuracy of the display will directly affect the accuracy of the printed output. Therefore, the color management of the display is an important basis for color management.
First, the principle and method of display color management
The color management technology of the display is mainly divided into calibration and characterization of the display. Display calibration refers to the process of setting and adjusting the optimal or specific display state. Optimal state refers to a neutral, colorless state that is adjusted by matching the display to achieve optimal brightness, contrast, and a certain color temperature. A specific state is a situation that mimics the appearance of a particular environment.
The display calibration system is divided into two types according to the use mode and principle:
Pure software
1 use method. Such as Adobe Gamma, MonitorCalibrator and other software, through state observation and manual settings to achieve an ideal or specific working condition.
2 working principle. The adjustment of the effect change is accomplished by adjusting the LUT table of the display card. The LUT table is a conversion table between the pixel values ​​of the display image and the driving values ​​of the display driving circuit.
2. Hardware and software cooperation (including colorimeter or spectrophotometer)
1 use method. Such systems as PrifileMaker, MeasureTool, and EyeOne all have a target state feedback detection and adjustment structure composed of a monitor colorimeter. The display panel buttons of this system can adjust the brightness, contrast and color temperature, and the display interface can be detected through a colorimeter. The interactive adjustment of the display data and the panel buttons reaches a certain target state.
2 working principle. The display effect is adjusted by displaying the change of the LUT table in the card. After reaching the set target state, the calibrated mapping table in the display card needs to be solidified. Fig. 1 is a schematic diagram of the adjustment mode of the soft-hard combination mode. The feature is that after setting a certain state, the calibration change is obtained through the mapping mode of the display card look-up table. The disadvantage of this system is that there is no direct recovery compensation for the performance degradation of the display. The calibration compensation based on the LUT of the display card is just a mapping change under the existing display capability.
After the display is calibrated, the ICC Profile in the corresponding display mode can be done. This process is called characterization.
Second, monitor color management experiment and analysis
In this experiment, Eye-One Match 3.0 display calibration software was used to monitor the color of the monitor, and the accuracy of the display calibration was analyzed through the data obtained from the experiment.
Experimental equipment
Hardware: Great Wall M176 LCD monitor, Eye-One Pro colorimeter.
Software: Eye-One Match 3.0 monitor calibration software, ProfileMaker Pro 5.0.5, Adobe Photoshop CS3.
2 monitor color management experiment
This experiment chooses Eye-One Match 3.0 correction software to carry on the color management to the monitor, Eye-One Match 3.0 is the software that is specially used for the display color management.
1 Control of experimental conditions
a. Under different lighting conditions, the same color will have a different color appearance. Therefore, it is required that the display be calibrated and measured under the same light source, a neutral gray environment is established, the light source is standardized, and the surrounding strong light is turned off, and a hood is preferably used. The D65 light source was used in this experiment.
b. Before correcting and measuring the display effect of the monitor, first clean the monitor screen, and be careful not to squeeze the screen while wiping; open the monitor for at least half an hour to make it color stable; turn off the monitor's color management function and screen saver.
2 monitor calibration procedure
a. Target the display: The target color temperature is set to 6500k; the target gamma value is set to 2.2; the target whitefield brightness is set to 120cd/m2.
b. Ambient light inspection. The appropriateness of ambient light will ultimately affect the success or failure of the experiment. In the course of the experiment, the ambient light must always be stable and strong light must not be present. The software comes with an automatic ambient light detection page. When the ambient light is in the proper state, the black slider is within the green range.
c. Contrast adjustment. Adjust the display contrast to the maximum, place the measuring device in the corresponding position, click the start button, and start adjusting the contrast. During this process, the contrast of the monitor is constantly adjusted until a satisfactory result is finally obtained, that is, the black slider is within the green range.
d. brightness adjustment. First, set the brightness value of the monitor to the lowest value. After clicking the start button, increase the brightness value according to the software prompt until the black slider is in the middle of the green range.
e. Adjust the monitor's R, G, B tristimulus values. After selecting the color temperature of the white point, place the screen correction instrument in the corresponding position and adjust the three color values ​​of the monitor R, G, and B until the black slider is in the middle of the green range.
f. Measure color blocks. By measuring the 42 standard color blocks included in the software, the graphics of the graphics card are automatically adjusted to match the target settings, thereby adjusting the overall performance of the display. The software automatically locates the position of the Eye-one. There are constantly changing color patches. The software compares the color information obtained by the Eye-one with the original color information and makes adjustments, as shown in Fig. 2.
3 Display characterization
After the calibration is completed, the characteristic curve of the display is obtained. The more the characteristic curve tends to be linearized, the more accurate the screen is corrected. Save the resulting ICC profile to: \WINDOWS \system32\spool\drivers\color and apply it to the system to complete the color management of the display, as shown in Figure 3.
3. Monitor calibration results chromatic aberration analysis
Use the Macbeth ColorChecker Chart to accurately evaluate the accuracy of monitor profiles and analyze the effects of monitor color management. The Macbeth ColorChecker Chart includes 24 color patches that cover most of the colors in the color gamut, and many of them represent memory colors and neutral colors, such as the color of skin, plants, and blue sky (Figure 4) Show), can accurately evaluate the monitor's color management effects.
Third, the experimental summary
The experimental results show that after using the Eye-One Match 3.0 to monitor the color of the monitor, the average color difference produced is 4.04, the maximum color difference is 7.8, and the color industry tolerance specified by the printing industry is ΔEab=6, so the objective evaluation from the color difference is From the perspective of view, the color difference of the display can be accepted by the printing industry. It is proved that with the Eye-One Match 3.0 color management software, the correct experimental method is adopted, the accuracy of the obtained characteristic document is very high, and accurate color management can be achieved.
To do a good job in monitor color management, note the following points:
1 Before performing color management on the monitor, the monitor must be warmed up for 30 minutes in advance and ambient light is controlled at neutral gray.
2 Select the correct monitor calibration 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 monitor regularly. The display will gradually age over time, performance will attenuate, and the color reproduction performance of the display will change. Therefore, it is necessary to regularly compare with the proofs, and use a screen correction instrument to periodically correct the display. The corrected items mainly include brightness, contrast, gamma, and fluorescent type.
4 Manage display ICC files.
5 Properly save the standard proofs. If any fades should be promptly replaced, the image files of the standard proofs should be kept permanently so that they can be used directly when the proofs fade.
First, the principle and method of display color management
The color management technology of the display is mainly divided into calibration and characterization of the display. Display calibration refers to the process of setting and adjusting the optimal or specific display state. Optimal state refers to a neutral, colorless state that is adjusted by matching the display to achieve optimal brightness, contrast, and a certain color temperature. A specific state is a situation that mimics the appearance of a particular environment.
The display calibration system is divided into two types according to the use mode and principle:
Pure software
1 use method. Such as Adobe Gamma, MonitorCalibrator and other software, through state observation and manual settings to achieve an ideal or specific working condition.
2 working principle. The adjustment of the effect change is accomplished by adjusting the LUT table of the display card. The LUT table is a conversion table between the pixel values ​​of the display image and the driving values ​​of the display driving circuit.
2. Hardware and software cooperation (including colorimeter or spectrophotometer)
1 use method. Such systems as PrifileMaker, MeasureTool, and EyeOne all have a target state feedback detection and adjustment structure composed of a monitor colorimeter. The display panel buttons of this system can adjust the brightness, contrast and color temperature, and the display interface can be detected through a colorimeter. The interactive adjustment of the display data and the panel buttons reaches a certain target state.
2 working principle. The display effect is adjusted by displaying the change of the LUT table in the card. After reaching the set target state, the calibrated mapping table in the display card needs to be solidified. Fig. 1 is a schematic diagram of the adjustment mode of the soft-hard combination mode. The feature is that after setting a certain state, the calibration change is obtained through the mapping mode of the display card look-up table. The disadvantage of this system is that there is no direct recovery compensation for the performance degradation of the display. The calibration compensation based on the LUT of the display card is just a mapping change under the existing display capability.
After the display is calibrated, the ICC Profile in the corresponding display mode can be done. This process is called characterization.
Second, monitor color management experiment and analysis
In this experiment, Eye-One Match 3.0 display calibration software was used to monitor the color of the monitor, and the accuracy of the display calibration was analyzed through the data obtained from the experiment.
Experimental equipment
Hardware: Great Wall M176 LCD monitor, Eye-One Pro colorimeter.
Software: Eye-One Match 3.0 monitor calibration software, ProfileMaker Pro 5.0.5, Adobe Photoshop CS3.
2 monitor color management experiment
This experiment chooses Eye-One Match 3.0 correction software to carry on the color management to the monitor, Eye-One Match 3.0 is the software that is specially used for the display color management.
1 Control of experimental conditions
a. Under different lighting conditions, the same color will have a different color appearance. Therefore, it is required that the display be calibrated and measured under the same light source, a neutral gray environment is established, the light source is standardized, and the surrounding strong light is turned off, and a hood is preferably used. The D65 light source was used in this experiment.
b. Before correcting and measuring the display effect of the monitor, first clean the monitor screen, and be careful not to squeeze the screen while wiping; open the monitor for at least half an hour to make it color stable; turn off the monitor's color management function and screen saver.
2 monitor calibration procedure
a. Target the display: The target color temperature is set to 6500k; the target gamma value is set to 2.2; the target whitefield brightness is set to 120cd/m2.
b. Ambient light inspection. The appropriateness of ambient light will ultimately affect the success or failure of the experiment. In the course of the experiment, the ambient light must always be stable and strong light must not be present. The software comes with an automatic ambient light detection page. When the ambient light is in the proper state, the black slider is within the green range.
c. Contrast adjustment. Adjust the display contrast to the maximum, place the measuring device in the corresponding position, click the start button, and start adjusting the contrast. During this process, the contrast of the monitor is constantly adjusted until a satisfactory result is finally obtained, that is, the black slider is within the green range.
d. brightness adjustment. First, set the brightness value of the monitor to the lowest value. After clicking the start button, increase the brightness value according to the software prompt until the black slider is in the middle of the green range.
e. Adjust the monitor's R, G, B tristimulus values. After selecting the color temperature of the white point, place the screen correction instrument in the corresponding position and adjust the three color values ​​of the monitor R, G, and B until the black slider is in the middle of the green range.
f. Measure color blocks. By measuring the 42 standard color blocks included in the software, the graphics of the graphics card are automatically adjusted to match the target settings, thereby adjusting the overall performance of the display. The software automatically locates the position of the Eye-one. There are constantly changing color patches. The software compares the color information obtained by the Eye-one with the original color information and makes adjustments, as shown in Fig. 2.
3 Display characterization
After the calibration is completed, the characteristic curve of the display is obtained. The more the characteristic curve tends to be linearized, the more accurate the screen is corrected. Save the resulting ICC profile to: \WINDOWS \system32\spool\drivers\color and apply it to the system to complete the color management of the display, as shown in Figure 3.
3. Monitor calibration results chromatic aberration analysis
Use the Macbeth ColorChecker Chart to accurately evaluate the accuracy of monitor profiles and analyze the effects of monitor color management. The Macbeth ColorChecker Chart includes 24 color patches that cover most of the colors in the color gamut, and many of them represent memory colors and neutral colors, such as the color of skin, plants, and blue sky (Figure 4) Show), can accurately evaluate the monitor's color management effects.
Third, the experimental summary
The experimental results show that after using the Eye-One Match 3.0 to monitor the color of the monitor, the average color difference produced is 4.04, the maximum color difference is 7.8, and the color industry tolerance specified by the printing industry is ΔEab=6, so the objective evaluation from the color difference is From the perspective of view, the color difference of the display can be accepted by the printing industry. It is proved that with the Eye-One Match 3.0 color management software, the correct experimental method is adopted, the accuracy of the obtained characteristic document is very high, and accurate color management can be achieved.
To do a good job in monitor color management, note the following points:
1 Before performing color management on the monitor, the monitor must be warmed up for 30 minutes in advance and ambient light is controlled at neutral gray.
2 Select the correct monitor calibration 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 monitor regularly. The display will gradually age over time, performance will attenuate, and the color reproduction performance of the display will change. Therefore, it is necessary to regularly compare with the proofs, and use a screen correction instrument to periodically correct the display. The corrected items mainly include brightness, contrast, gamma, and fluorescent type.
4 Manage display ICC files.
5 Properly save the standard proofs. If any fades should be promptly replaced, the image files of the standard proofs should be kept permanently so that they can be used directly when the proofs fade.
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