At the turn of the 16th century, especially in Northern Italy, artists began to use new techniques in the manipulation of light and darkness, such as the tone contrast evident in many of Titian's portraits and the development of sfumato and chiaroscuro by Leonardo da Vinci and Giorgione. The period also saw the first secular (non-religious) themes. Debate has ensued as to the secularism of the Renaissance emphasized by early 20th-century writers like Jacob Burkhardt due to the presence of these - actually few - mythological paintings. Botticelli was one of the main painters whose secular work comes down to us today, though he was deeply religious (a follower of Savonarola) and painted plenty of traditional religious paintings as well.. ❚