Fra Angelico (1400-1455, roughly) : Fra Angelico, or Giovanni da Fiesole, was a friar who painted altarpieces and panels, sticking only to religious subjects, as befitted a man of the cloth. He was a leading early Renaissance painter, showing off his newfound knowledge of perspective like every other painter of the era, but he also had a fine sense of line. IIRC, he was a fine portraitist for the time, also (but that doesn't mean much).