What is the meaning of the gray card, black card and white card in photography?

Gray card: it is the benchmark for accurately detecting exposure. Photos with rich layers and saturated colors come from accurate exposure. If the light of the shooting scene is too bright or too dark, it may lead to exposure deviation. The gray card can balance the scene with complex light into 18% neutral gray. By recording the reflected light of the gray card with an exposure meter, you can get an accurate exposure value!

Photographers who consulted the records of Chengdu Center learned that most gray cards and white cards were used to measure white balance manually. Of course, the white card can also be used as a reflector (but it is only suitable for very small objects, and the area is always limited). Black cards are usually used to block stray light, or one of the props used to block the lens in order to make the exposure of different parts of the picture average.