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.
Raphael
Raphael was one of the finest draftsmen in the history of Western art, and used drawings extensively to plan his compositions. According to a near-contemporary, when beginning to plan a composition, he would lay out a large number of stock drawings of his on the floor, and begin to draw "rapidly", borrowing figures from here and there. Over forty sketches survive for the "Disputa" in the Stanze, and there may well have been many more originally; over four hundred sheets survive altogether. He used different drawings to refine his poses and compositions, apparently to a greater extent than most other painters, to judge by the number of variants that survive: "... This is how Raphael himself, who was so rich in inventiveness, used to work, always coming up with four or six ways to show a narrative, each one different from the rest, and all of them full of grace and well done." wrote another writer after his death. For John Shearman, Raphael's art marks "a shift of resources away from production to research and development".