Rembrandt lighting is a basic portrait lighting technique that uses a single key light at a 45 degree angle to illuminate one side of the face, leaving the other side in shadow but with a triangular catchlight. It creates a classic chiaroscuro effect. While the ideal triangle shadow is no wider than the eye and shorter than the nose, in practice it can be difficult to achieve perfectly so Rembrandt lighting is often used loosely to mean roughly half the face lit. The key light is sometimes supplemented by a reflector or lower powered fill light to lighten the shadows on the dark side of the face.