Tuning and Soft Proofing (3)

What is color temperature, Gamma and LUT
Suppose there is an idealized Black Body. When we provide heat to this black object, it generates radiation/radiation. Some of the spectrum of the emitted electromagnetic waves is visible to the human eye (these are the light ). When heat is applied to the black object at different temperatures, the energy and spectral distribution (light color) of the emitted light will also differ from this temperature. It is the color temperature we often say. In the monitor, low color temperature is the color reddish yellow warmer, high color temperature is the color blue and cold. In general, the standard color temperature for the prepress process is 5000K, so the monitor should also be calibrated to 5000K.

The gamma value is actually the relationship between input and output. The scanning system has Gamma, the display system has Gamma, and the print also has Gamma (but usually called Dot Gain). The lower the gamma value is, the lighter the color is, the higher the gamma value is, the darker the color is, and the Gamma1 is linear. The gamma value in the display system is the relationship between the RGB values ​​in the file (input) and the light output (output) of the display. The shop often emphasizes that the Gamma value of the Mac machine must be 1.8 and the PC is 2.2 when tuning the monitor. In fact, there is no explicit provision for this. The reason why the Mac is set to 1.8 is because Apple's Gamma (Dot Gain) was 1.8 when it launched the first LaserWriter. Therefore, it is recommended that the display system of the Mac be adjusted to 1.8 so that the screen and print product are the same. But today, when we use CMS, because the ICC Profile of the monitor has recorded the gamma value of the entire display system, even if we use Gamma4, the desktop will become very dark, but it can be seen in the software that supports ICC. The color will still be correct. In general, Gamma2.2 is a suitable setting. Because the gamma of the picture tube is mostly about 2.2, when using 2.2, the adjustment system does not need to make too many gamma modifications in the LUT, so that the gradual change is smoother.
There are three LUTs, which are RGB. The input and output are also from 0 to 255. When the output of each Channel is also 255, it is equal to 256 levels per channel, the overall color available is 256X256X256, etc., and the color is 167,000. That is, the power of the 8th of each Channel2, or 2 to the 24th, or 24-bit color.

To mention that, there is no standard for the brightness and contrast of the display, which means that when there are multiple displays with the same brand, or a display mixed with other brands, the brightness and contrast of each part are adjusted after the additional display adjustment system is adjusted. There may also be differences. Some of the additional monitor adjustment systems are purely based on the human eye to adjust the luminosity and contrast, and others are recommended to adjust the luminosity and contrast to a certain value after measuring the instrument. Both words, the latter is more accurate. However, if the monitor is in use at a high time, the photometric output is insufficient, and it is difficult to match the brightness and contrast with other newly used monitors. All of Barco's displays have the same standard of brightness and contrast, so when setting the factory's value, each part can be the same. (To be continued)