Optics · a Light

A dark room with a pinhole gave the camera its name

Make a small hole in the wall of a dark room and the scene outside appears on the opposite wall, upside down. The effect was noticed long before anyone explained it. It is described in the Chinese Mozi text around the fourth century BCE, and a Greek work handed down under Aristotle's name notes that gaps between leaves cast crescents on the ground during an eclipse. Ibn al-Haytham, in Cairo in the early eleventh century, turned it into an experiment. He set several lamps outside the aperture and showed their images stayed separate on the wall, which means light travels in straight lines and rays do not mix. His term was the dark room. Kepler put that into Latin in 1604 as camera obscura.

Ibn al-Haytham · Cairo, early eleventh century