Screen correction considerations
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Screen calibration definition
In the past, many people said that the screen calibration is to adjust the screen to look like printed matter. The general practice is to use a printed manuscript as a benchmark and then use some software such as Gamma provided by Adobe or directly use it. The adjustment function on the display to achieve a color similar to or the same color as the print. But this is a way of not having an ICC workflow before, this way can only achieve the purpose of the draft, or it may not be the same result for each software. The main thing is that there is no central control part to unify the color, so Apple developed a system extension program called ColorSYnc a few years ago. This is the ability to use the system software to centrally handle color, but the central controller needs some information about the color characteristics of different devices. This information is called ICCProfile, and to generate these ICCProfiles requires appropriate hardware and software to be successful.
The first job of screen calibration
Screen calibration can be divided into two parts. The first is the environment control. Because the screen is a transmissive display, the surface of the screen tube is also affected by the light around the environment, such as when the light is directly on the screen. The contrast of the image will decrease in real time. The reason is that the light in the room is reflected on the glass of the picture tube, so that the black part cannot produce enough black. If the indoor lights are turned off, the contrast on the screen suddenly increases, but I believe that no one likes to work in an all-black environment, making workers feel uncomfortable. A better method is to properly control the lighting in the room so that the light cannot directly shine on the picture tube glass. A very effective method is to add a light blocking part to the screen.
Stable and standard lighting
Just said that the light in the room is properly controlled so that the contrast of the screen has good results, but many friends will ignore the illumination of the original. When we control the light can not illuminate the screen, the illumination on both sides of the screen is insufficient, and the color temperature Not allowed, so it is best to have a stable and standard reading light box. This light box is usually precision designed, generally an international standard of 5000K color temperature, and the light reflection angle does not cause reflection, and the illumination is average.
Color temperature ClolrTemperature
The color temperature is used to refer to the degree to which the light color is relatively white to quantify the light color performance of the light source. According to the scientific theory, a standard black body with complete absorption and radiation capability is heated, and the temperature gradually increases. The temperature of the black body is heated to the temperature when the light source is close to the light source, which is defined as the correlated color temperature of the light source. , referred to as the color temperature, for the absolute temperature K (Kelvin, or Kelvin temperature) as a unit.
The lighter the color, the higher the color temperature; if it is red, the lower the color temperature. During the day, the light color of the day also changes with time; in the 40 minutes after sunrise, the light color is yellower and the color temperature is 3000K; the midday sun is white, rising to 4800~5800K, and the cloudy day is about 6500K at noon; the light color is red before sunset. The color temperature dropped to about 2200K. In the artificial light source, there are tungsten light bulbs 2000~3400K, general beige light tubes 2600~4000K, general white light tubes 6000~8000K, and our design printing industry needs 5000K standard color light tubes.
Why do you have a standard shade? Because of the 5000K color temperature source.
(a) in the middle of the visible spectrum,
(2) It is a white light with a balanced color.
(3) It will not be biased towards any color,
(4) Internationally recognized standards.
It is very difficult to copy all the colors on the computer screen. Everyone understands that it is impossible to display the image on the screen without deviation on the screen, because the colors on the screen and the paper are completely different. Physical phenomena are produced.
Screen calibration and characterization
It is very difficult to copy all the colors on the computer screen. Everyone understands that it is impossible to display the image on the screen without deviation on the screen, because the colors on the screen and the paper are completely different. Physical phenomena are produced. The color display of different brands of screens can be very different, and the temperature of the screen is another factor; after the same screen is turned on for several hours, the displayed colors may also be different, and the hardware aging also affects the stability of the color display; Phosphorus will decay over time. Finally, the external light sources in your work environment will also work, as they will blend with the colors emitted by the screen when they are projected on the screen.
The unadjusted screen has a higher white point color temperature, and its color temperature is between 8000 and 9500K, which is obviously blue. In order to make the color between the screen and the draft or printed product close, you should set your screen white point (WhitePoint) to match the color temperature of the indoor bulb when you look at it. And setting the appropriate gamma value (Gamma) is to adjust the contrast of the screen display to match the draft or print. The steps for screen calibration are as follows:
(1) Fix the light at the working position first, or use the standard color light box for the color.
(2) Turn on the screen for at least 30 minutes to allow the picture tube of the screen to reach a stable state.
(3) Turn off the desktop pattern and change the background of the screen to medium gray, so as to avoid the interference of the background color.
(4) Start the screen calibration software.
(5) Follow the software instructions to adjust the light and darkness of the screen, and use the tape to be pressed or pressed with software.
(6) The white color temperature and the contrast value are selected. The usual printing requirements are WhitePoint 5000K and Gamma 1.8.
(7) A colorimeter or spectrophotometer is sorbed at a specified position on the screen.
(8) Store the measured data and ICCProfile.
The above is the general screen calibration steps, the following is the actual working situation, first use AppleClolrSync's DefaultCalibrator, which is a free and simple screen calibration tool to help you calibrate the gamma and white point of the screen. The method of use is very simple, just follow the instructions of the software, because the single * eye observation to correct, the accuracy will be poor, if you want more accurate screen calibration, you may need some equipment, these devices contain a colorimeter, It measures the color of the light emitted by the screen through an instrument attached to the screen. Screen calibration software commands emit different colors on the screen. The color emitted by the chroma metering screen sends the data back to the computer, comparing the actual measured color to the color that should be displayed, so you can adjust the color temperature and gamma settings to achieve a certain set of goals.
Finally, how to check whether the color and lightness of the screen display are moderate, teach you a simple method, open a blank window on the screen, then put a blank paper under the color light source, and then open two with a piece of paper. Hole, through the paper to observe the color and darkness of the two holes. If the color temperature is not correct, the color temperature control in the software can be corrected. If the light darkness is wrong, the intensity of the light source should be changed, so the dimming is required. The light box is easier to get the desired effect. If you want more accurate readings, you can use the light-weight meter that is easier to use to measure the white level on the screen and the white paper reading under the color source. The color temperature can be measured by the color temperature meter.
Finally, please remind everyone that if you have a screen calibration program on your system, you can not use other calibration software such as AdobeGamma or AppleClolrSyncDefaultCalibrator at the same time.
After the screen calibration is completed, it needs to be recalibrated only when the conditions change, or it is proposed to recalibrate once a month if its illuminant "drift" changes. A good way to do this is to fix the brightness and contrast adjustments of your screen with adhesive tape after the calibration is complete, and keep the lighting conditions intact.