Gianfrancesco Penni
Born in Florence to a family of weavers, Penni entered Raphael's workshop very early in his life, and collaborated with him on several works, including the famous Rooms of the Vatican Palace, as well as the frescoes of Villa Farnesina, both in Rome. Heinrich Wölfflin and some other writers credited him with the entire execution of the Raphael Cartoons, with Raphael only creating the initial design, though more recent writers believe Raphael did much of the work himself.
Sprezzatura
Raphael as an artist exemplified "sprezzatura" from the beginning of his career, starting with his first signed work "The Marriage of the Virgin". "Inspired by his teacher Perugino's rendering of the same subject, Raphael's painting can be found to differ primarily from its model by its unique awareness of the importance of "sprezzatura"."