The Camera Obscura is a natural Phenomenon, and has a long history. In its simplest form it is a small hole (aperture) through which light passes from an object outside into a darkroom. The image appears upside down on the wall opposite the hole.
Rene Descartes 'La Dioptrique' 1637A camera works just like a human eye - as seen in this picture of the eye as a camera obscura from Rene Descartes 'La Dioptrique.
The size of the hole will affect the sharpness of focus and the brightness of the image (look here, here and here to make your own camera obscura).
In the 4th Century BC Aristotle wrote about the phenomenon. Around the same time Mohist philosophers in China also noticed the phenomenon.
|The artist David Hockney has written a book and a documentary called ‘Secret Knowledge’ where he suggests that the Camera Obscura was used by renaissance artists.|
The documentary can be watched here – 'Secret Knowledge or here