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
Vasari emphasises that Raphael ran a very harmonious and efficient workshop, and had extraordinary skill in smoothing over troubles and arguments with both patrons and his assistants—a contrast with the stormy pattern of Michelangelo's relationships with both. However though both Penni and Giulio were sufficiently skilled that distinguishing between their hands and that of Raphael himself is still sometimes difficult, there is no doubt that many of Raphael's later wall-paintings, and probably some of his easel paintings, are more notable for their design than their execution. Many of his portraits, if in good condition, show his brilliance in the detailed handling of paint right up to the end of his life.