What does the exposure basis 18 gray mean?

Add LZ You can understand at a glance.

As you can imagine, this "gray scale", in layman's terms, refers to the depth of color. You should know that black and white photos can be divided into shades, and different colors also have different shades. As you said, red, the color is red, so is it "deep red" or "light red" or "neither deep nor light red"? This change in depth is different levels of gray.

The utility in practice is not much to say, and everyone speaks very well. In life, it is not difficult to take 18% ash. The small gray cover of Kodak film box is just like the gray scale of 18%. Everything that looks similar in color depth, lightness and darkness can be regarded as the same gray level. Find one, have more time to practice and compare with the real thing, and you will have experience.