Variation of indoor light from day to night

Generally speaking, on sunny days, after sunrise and before sunset, the color temperature of direct sunlight is low, and gradually increases near noon. The equilibrium color temperature of Sunlight film is 5500K, which is the color temperature of direct sunlight at noon. This color temperature is generally stable from three hours after sunrise to three hours before sunset. In fact, outdoor natural light is a combination of direct sunlight and diffuse light in the sky; At noon, the color temperature of pure sunlight is only about 5000K, and the color temperature of sky diffuse light is about 12000 ~ 18000 K, and the combined color temperature of these two light sources is 5500 K. In the weather covered by thin clouds, the direct sunlight is covered by thin clouds, and the color temperature is about 6500 K ~ 7000 K higher than that of sunny days. The light on cloudy days is diffuse light from clouds, and the color temperature is about 7000 K ~ 7500 K ..