The term luminism was introduced by mid-20th-century art historians to describe a 19th-century American painting style characterised by effects of light in a landscape, through the use of aerial perspective and the concealment of visible brushstrokes. Luminist landscapes emphasise tranquillity, and often depict calm, reflective water and a soft, hazy sky. The term has also been used to describe some later European works, such as the early paintings of Piet Mondrian.