From the discovery.com article:

Italian Renaissance painter Caravaggio used revolutionary optical instruments to “photograph” his models more than 200 years before the invention of the camera, according to a researcher in Florence.

The 16th-century artist celebrated for his dramatic chiaroscuro (light and shadow) paintings mastered “a whole set of techniques that are the basis of photography,” Roberta Lapucci said.

Caravaggio worked in a “darkroom” and illuminated his models through a hole in the ceiling, said Lapucci, who teaches at the prestigious Studio Art Centers International in the Tuscan capital.

The image was then projected on a canvas using a lens and a mirror, she said.

Caravaggio “fixed” the image, using light-sensitive substances, for around half an hour during which he used white lead mixed with chemicals and minerals that were visible in the dark to paint the image with broad strokes, Lapucci said.

She has hypothesized that Caravaggio used a photoluminescent powder from crushed fireflies, which was used at the time to create special effects in theater productions.

One of the main elements of these mixtures was mercury — to which prolonged exposure can affect the central nervous system causing irritability and other symptoms — which Lapucci said would help explain Caravaggio’s notorious temper.