Isleworth Mona Lisa
According to Leonardo's early biographer Giorgio Vasari, Leonardo had started to paint "Mona Lisa" in 1503, but "left it unfinished". However, a fully finished painting of a "certain Florentine lady" surfaced again in 1517, shortly before Leonardo's death and in his private possession. The latter painting almost certainly is the one that now hangs in the Louvre. Based on this contradiction, supporters of the authenticity of the "Isleworth Mona Lisa" claim it is the unfinished "Mona Lisa", made at least partially by Leonardo, and the Louvre "Mona Lisa" a later version of it, made by Leonardo for his own use.
Mona Lisa
Before its completion the "Mona Lisa" had already begun to influence contemporary Florentine painting. Raphael, who had been to Leonardo's workshop several times, promptly used elements of the portrait's composition and format in several of his works, such as "Young Woman with Unicorn" (c. 1506), and "Portrait of Maddalena Doni" (c. 1506). Celebrated later paintings by Raphael, "La velata" (1515–16) and "Portrait of Baldassare Castiglione" (c. 1514–15), continued to borrow from Leonardo's painting. Zollner states that "None of Leonardo's works would exert more influence upon the evolution of the genre than the "Mona Lisa". It became the definitive example of the Renaissance portrait and perhaps for this reason is seen not just as the likeness of a real person, but also as the embodiment of an ideal."