What do people use to measure light?

Under normal circumstances, the mode of spot metering is basically used to shoot portraits. When using spot metering mode for metering, we can see a red metering point in the viewfinder. When taking a portrait, we can put the metering point on the eyes, hair, face or clothes of the subject as needed.

Spot metering refers to metering a point, which is usually the center of the whole picture, accounting for about 9% of the whole picture. The advantage of this method is that it can measure the most suitable place in a certain picture according to the photographer's preference, and it is not affected by other factors, especially when the contrast between light and dark in the scene is strong, or the subject can measure the light correctly without interference from other nearby lights.