Gellée did not really appreciate copyists and went as far as publishing an album titled «Liber Veritas» (The book of truth) in which he had reproduced some 200 of his works in order to warn collectors.
Jacques Callot, a celebrated engraver, was copied by Jean Leclerc, Abraham Bosse or Claude Dervet.
As for the Le Nain brothers no one really knows who was the best artist between Antoine, Louis and Mathieu; perhaps Louis according to certain specialists.
Louis's works were often mistaken with those of Georges de La Tour while the
Le Nain brothers had themselves some imitators, notably Jean Michelin.
De La Tour only became known during the first third of the 20th Century and many of his works had been previously attributed to French, Italian and Spanish masters such as Herrera, Murillo or Zurbaran.
Many paintings have now been authenticated as by La Tour whose style closely resembled that of Gerrit Honthorst.
Charles Le Brun, official painter to the French court, often copied old masters and worked with the assistance of many aides, notably his nephew François Verdier, Claude Audran and Charles de La Fosse.
Le Brun's main rival, Pierre Mignard, copied the works of Rosso, Primaticcio, Carracci and Guido Reni but was also copied by Charles Dufresnois.
Philippe de Champaigne had two main assistants, his nephew Jean-Baptiste and Nicolas Plattemontagne who adopted his style and thus created some confusion about the authorship of several works.
There is also much confusion regarding the works of a family of painters called Parrocel as there were 16 painters bearing that name and it's not always easy to distinguish between the true authors of many paintings.
Ignace Parrocel's works were mistaken with those by Pierre or Joseph-François Parrocel while Charles Parrocel copied Rubens, Van Dyck or Jacques Courtois.