Camera obscura – latin for ‘dark room’. – http://brightbytes.com/cosite/what.html
An optical device that led to photography and the photographic camera. Camera obscurer consists of a dark room or box with a hole in the side. When light from outside of the box comes through the hole is projects onto the opposite wall. The picture is as accurate as if you were looking at the outside itself, the colours and perspective are the same except the image is upside down. This is due to the fact that light travels in straight lines and when the light passes through the small hole turns the image upside down. This is the same as our eyes except our brains put it the right way round, you can do the same with camera obscurers except this involves mirrors.
If the hole is made smaller the image becomes more defined but dimmed from light but if the hole is made larger the definition becomes less and the image becomes brighter.
Camera obscura dates back to 390bc in the writing on Mozi a Chinese philosopher, he correctly asserted that the image is flipped upside down because light travels in straight line. It is a known fact that in the 17th century painters used camera obscurer to paint accurate portraits, it is thought that Johannes Vermeer painted ‘Girl with a pearl earring’ using a camera obscura although it is not certain. In 1490 Leonardo da vinci there was 2 clear descriptions of the camera obscurer in his notebooks, showing that he too as a painter used this device. Although at the time other artists saw this as cheating so use of the camera obscurer was not widely appreciated.
How to make a camera obscura – http://content.photojojo.com/diy/diy-turn-your-room-into-a-walk-in-camera/