What is high-grade ash? How to achieve high-grade gray in the later stage of photography?

What is "advanced ash"? How is it formed?

For ordinary people, color and color are almost synonymous, but in the field of painting, color is a dynamic relationship between colors. We can't call an irrelevant and relatively simple color, such as a single piece of green. Under the concept of intrinsic color, we can say that its hue is green, and it is just a piece of color rather than a color relationship. Color is absolute, and color is relative. It may not care much about the accuracy of hue, but it attaches great importance to the changing relationship between specific objects and surrounding objects. For example, the dark part of a white interlining is painted with black characters on a white background, which will look straightforward and blunt. If the surrounding environment and light source are changed into a color that looks like white instead of white (maybe a little blue or a little purple or other colors), and the interaction of surrounding colors, this non-white color can show richer images, and it will not make people feel that the white interlining has become a blue interlining or interlining of other colors. This kind of color carrier with rich color relations produced by conditional conversion is called "gray".

Because the process of gray is complex and changeable, some phenomena are very easy to be misunderstood, black and white are indistinguishable and confused, and gray becomes an unpleasant color. Even in the color of language, there are generally gray, gloomy, gray and gray-headed, and then there are gray grandchildren, frustrated, excessively pale, disheartened and exaggerated. Long-term inherent concepts, whether the understanding of colors or the expression of emotions, may reflect the reality of the objective world under certain conditions, but they are easily modeled in the form of painting, and the concepts become rigid and irreconcilable with the dynamically generated "gray".

Beginners are most likely to make "gray" mistakes, for example, they can't distance themselves from each other in lightness, or introduce too many colors in pursuit of color richness unilaterally, or repeat colors too many times like mixing cement, so that colors lose their luster, or treat them evenly without inclination. In order to distinguish it from the phenomenon of turbid and messy colors and gloomy pictures, someone added the word "advanced" in front of the beautiful gray with proper color relationship. This is the origin of "advanced ash".

Everyone who paints knows this sentence: When you master gray, you master the essence of color.

Then Baidu: PS later color matching "advanced gray"