It has been known for some time that Caravaggio used to work in a 'dark room' as he painted, and it had been suggested that the preponderance of left-handed figures in his artwork indicated that he had made use of the camera obscura. However, recent evidence suggests that he had actually developed* a photographic process using materials including lead and crushed up fireflies- 200 years prior to the 'invention' of photography.

According to this New York Times Article- it also accounts for his chiaroscuro style of painting and for his violent temper. Prolonged exposure to mercury can have an adverse affect on the central nervous system.

*no pun intended