A portrait can painted in differing hues and backgrounds with subtle changes to the subject as in Van Gogh's L'Arlésienne and Claude Monet's Rouen Cathedral.
Another type is where the same subject is painted at different times of day or seasons of the year for example Claude Monet in his Poplars, Haystacks.
This was a common practice for Leonardo da Vinci, Michelangelo and most of the other classical artists although most of their studies and sketches did not survive.
used with permission, This poem may be copied if authorship is included and used for educational purposes only) John Coplans supplied a critical approach in an exhibition at the Pasadena Art Museum in 1968.
Pasadena Art Museum 1968, New York Graphic Society, 1968 • Eric Ericson: “To Everything a Season”, What Say You?