How to give full play to the side light in portrait photography

There are two kinds of indoor portrait shooting, one is on-site light photography, which uses on-site light as the only light source to shoot images. There is also an indoor portrait that uses artificial light, that is to say, a photographic lamp is used to distribute the light. Generally, a main light, an auxiliary light and a background light are needed. The light ratio of a general digital camera is 1: 2. As long as this light ratio is set, exposure can be carried out in the strong light area, which means that the main light is twice as bright as the auxiliary light. The background light is set behind the subject to illuminate the background, making the subject stand out in the background.