This is one of a series of oil sketches by Rubens representing the life of Constantine, the first Christian Emperor of Rome. Commissioned by the French Royal tapestry works, they were later repeated as full-scale cartoons from which tapestries were woven (in the process the composition is reversed). Rubens often used painted sketches to transmit his ideas. He used a small oak panel prepared with a white chalk ground and a roughly applied brown priming.