A special type of lighting is light reflected consciously or accidentally from surfaces close to the photographed object. We call them residual light. It should not be underestimated. It is an important element of lighting and is the best, the most natural additional illuminating light. Lightens deep shadows to a very weak degree, but usually sufficient to extract their details. Therefore, it is recommended, so that the walls of the photo studio are bright, White. Painting the interior of the studio with dark paints is at least a misunderstanding.
Residual light plays an essential role in daylighting in a room, dimly illuminating the inky black shadows.
In the open air, this light occurs in the form of rays reflected from large ones, bright surfaces, for example: from the white walls, rocks, water. Residual light is also rays reflected from the blue sky and white clouds. All of this, of course, can happen on a sunny day, when the sun's rays directly illuminate the object.
The importance of residual light was recognized in the 1920s, when the industry began to produce highly sensitive emulsions with high irradiation tolerance. The residual light is too weak, so that, within the limits of the correct irradiation, it can react to low-sensitive emulsions.
The size of the screens should be adjusted as needed, because the same rules of the degree of dispersion apply here depending on the angle of light, what with non-reflected light.
Sometimes to get reflected lighting, we can use mirrors.