The camera obscura (or pinhole camera) was the earliest way that people could project images onto a surface. The Latin name means ‘dark room’. The method works best when a pinhole is cut in a surface which projects the image from brighter surroundings onto the opposite surface of a darkened chamber. The image will be inverted and reversed as the rays of light travel through the hole and cross over to the opposite side of the surface projection.
Some have suggested that this technique was known as long ago as the Stone Age. Paleolithic cave paintings show distortions in the shapes of animals, which could possibly have happened because the artist in the cave was tracing a slightly unstable projection on the cave wall. Small holes in some Neolithic structures might also have been inspired by the religious desire to project the sun’s image.
At some point in the first millennium BC, Chinese sundials started to use a small hole in the gnomon (the part of the sundial that creates the shadow) to project a pinhole image of the sun, which gave a more accurate measure of the time of day. However, it is not until the fourth century BC that we have a clear reference to the camera obscura, in the writings of a philosopher called Mozi. He described the way an inverted image appears in a ‘collecting-point’ or ‘treasure house’.
How the pinhole image in a camera obscura is projected.
It is thought that the ancient Greeks used pinhole projections to study solar eclipses and other phenomena. For instance, Aristotle comments on the conundrum that light from the sun travelling through a square hole nonetheless projects a circular image of the sun. But other than that, there are no clear Western descriptions of the camera obscura until the eleventh century, so this is probably another case in which the Chinese were a long way ahead of the West.