Practical Color Management Screen Correction and Twilight Light Source (2)

It is difficult to reproduce all colors on a computer screen. Everyone understands that it is impossible to display the images on paper without any deviation because the colors on the screen and the paper are used. A completely different physical image emerges.

Phosphor screen calibration and characterization

It is difficult to reproduce all colors on a computer screen. Everyone understands that it is impossible to display the images on paper without any deviation because the colors on the screen and the paper are used. A completely different physical image emerges. The color display of different brands of screens can vary greatly, and the temperature of the screen is another factor: the color of the display may be different after the same screen is turned on for several hours, and the hardware aging also affects the stability of the color display. : Phosphorus on the screen will decay over time. Finally, the external light source of your work environment will also work, because when they are projected on the fluorescent screen, they will mix with the colors emitted by the screen.

The color temperature of the unadjusted screen is higher, and its color temperature is between 8000 and 9500K, which is obviously blue. In order to make the color between the screen and the original or finished product close, you should set your white point to match the color temperature of the room light bulb when you color it. And the purpose of setting the appropriate gamma (Gamma) is to adjust the contrast of the screen display to be consistent with the print or print. The screen calibration steps are as follows:

(1) Fix the light in the working position first, or use the standard color light box for color matching.

(2) Turn on the screen for at least 30 minutes to allow the screen tube to reach a stable state.

(3) Close the desktop pattern and change the background of the screen to a medium gray so as to avoid interference with the background color.

(4) Start the screen calibration software.

(5) Follow the software instructions to adjust the light and darkness of the screen. Use adhesive tape to press the system or lock it with software.

(6) Select the color temperature and contrast of the white point. Usually the printing requirements are: WhitePoint is 5000K and Gamma is 1.8.

(7) The colorimeter or spectrophotometer is sucked on the screen at the designated position.

(8) Follow up with the measured data and ICC Profile storage.

From the Control Panel, open the Monitors & Sound or Monitors window, select the Color button, and then press Calibrate. Follow the instructions in the window to do it. It is recommended to use Expert Mode so that there are more options for color temperature and gamma settings. Select an appropriate color temperature value until the white spot on the screen is similar to the white color in the black light box. Select the appropriate gamma value until the image contrast on the screen is similar to the one in the black light box. The value usually used for printing is 1.8. Start the screen calibration software and select the color temperature and contrast value of the white point. Usually the printing requirements are: White Point is 5000K and Gamma is 1.8. The colorimeter or spectrophotometer is sucked in the designated position on the screen. Compare the actual measured color to the ideal color, so that you can adjust the color temperature and gamma to achieve a set target. The colorimeter can be used to measure the actual white color temperature and contrast of the screen.

The above is the general screen calibration procedure. The following is for everyone to explain the actual work situation. First, use AppleColorSync's Default Calibrator, which is a free and easy screen calibration tool to help you calibrate the screen gamma and white. point. The method of use is very simple. Do not follow the instructions of the software (see the figure above), because the accuracy will be poor if you rely on eye observation. If you want more accurate screen calibration, you may need some equipment. These devices include a Colorimeter, which measures the color of the light emitted by the screen through an instrument attached to the screen. The screen calibration software commands different colors on the screen. Color Measure The color emitted by the screen, sending the data back to the computer, comparing the actual measured color to the ideal color, so that you can adjust the color temperature and gamma settings to achieve a set target.

Finally, how to determine whether the color and brightness of the screen display are moderate, and teach everyone a simple method. Open a blank window on the screen, and then put a blank sheet of paper under the ochre light source. Then use a piece of crepe paper to open two holes. Use the crepe paper to observe the color and darkness of the two holes if the color temperature is not correct. Can pull the software in the color temperature control to correct, if the darkness is not correct, you need to change the intensity of the light source, so you need to have a dimmable light box easier to get the desired effect. If you want to have more accurate readings, you can use the key photometer for photography to measure whether the white reading on the screen and the white light under the black light source are consistent, and the color temperature can be measured with the color temperature meter.

Lastly, let's remind everyone that if you have a screen calibration application on your system, you cannot use other calibration software such as Adobe Gamma or Apple Color Sync Default Calibrator at the same time.

After the screen is calibrated, it must be recalibrated only when the conditions are changed, or it is proposed to recalibrate once a month when its "drift" of the luminaire changes. There is a good way to fix the brightness and contrast adjustment of your screen with adhesive tape after the calibration is done, and keep the lighting conditions constant.

Regarding how to use the appropriate ICC Profile for screen color preview or digital printing, we will leave it to the next stage and introduce it to everyone. If readers want to quickly grasp the methods of color management, please pay attention to our color management courses. .