Traditional Culture Encyclopedia - Photography major - What is the gray board in photography and what is its function?

What is the gray board in photography and what is its function?

18% gray board is the standard of photometry of exposure meter or camera. When the brightness difference between the background and the subject is large, or although the brightness is different, the proportion of the subject in the picture is small, it may be because of the accuracy and method of photometry that the subject is inaccurate. At this time, the exposure meter (or the exposure meter in the camera) can be used in the same direction of the main body.