What color is the 25-degree gray photo?

gray refers to the value of gray chromaticity, such as 2 degrees and 6 degrees, which is actually the proportion of black. When black and white are mixed, it is called gray, and the proportion of black points is how many degrees of gray.

photography photometry takes 18% reflectivity as the exposure reference value. (Because the photometry system commonly used by cameras takes the gray of the 18-degree gray board as the reference value, when the measured value of the pure black subject or pure white subject is compared with the 18-degree gray board, there will be great errors, resulting in overexposure or underexposure of the actual photometry value! )

the gray scale of a black-and-white image * * * is 256, which is -255 in numerical terms. By how many degrees of gray scale, we actually express the gray scale of 256 as a percentage. People's skin color is close to 18 degrees of gray, which actually means that black components account for 18% in pure white, so we can also know that white accounts for 82%, from which we can calculate that in RGB.