French art movement of the late 19th century that, inspired by scientific knowledges about the physical compositions of colours, tried to render them in an exact as possible way. To this purpose the impressionists went into nature (plein-air-painting), to catch their subjects as they were. The surrounding light conditions let contours blur and the visual impression prevails (Atomization of the objective world).
The double portrait depicts two real persons that are related to each other, often man and wife. It follows the physiognomy of the persons and it ensures a recognizability. Effigies of couples and friends are typical examples of the double portrait, which is quite different fom the representation of two random persons.