Grating of photographic lamp Why is there a grid on the wall?

The grid of the photographic lamp has a grid pattern on the wall, which is the AC component of the driving output voltage and current of the lamp. According to the relevant data, it can be eliminated if the input and output filter devices are appropriately added. Because LED lamps are basically driven by direct current. This happens when the content of communication is too high. Nowadays, many manufacturers sacrifice product quality for the purpose of reducing costs. Because people's eyes are time-delayed. The refresh frequency is not high enough. So I can't see it, and the refresh frequency of the camera is fast enough. So it can capture.