One use of studio lighting is to create a chiaroscuro effect, similar to Rembrandt lighting. The chiaroscuro technique shadows part of the subject’s face, completely or, mostly obscured by darkness, with other part in bright light. This term is also used in paintings and art, which came hundreds of years before its use in photography.
This is a strong example of the classic use of Rembrandt lighting in classic art. Both of the woman’s face have dark and light areas, and the first lady has her face turned, but still shows a defined circular curve of darkness on her face