Having attractive fill lighting is something that can really separate the pros from the amateurs when it comes to cinematography and photography. Close, soft light is most ideal, especially when filming and photographing women (where harsh light and shadow demarcations are undesirable), but the security mirrors which are the human iris have a tendency to reveal artificial shapes in distracting ways. Thus, circle or ring lights are the preferred way to get closeups, as the circles of illumination reflected in the liquid-coated human iris seem natural and organic.