How Does It Work?

The camera obscura is based on the principle that light travels in straight lines. Only a few of the rays of light from each detail of the scene outside the camera are properly aligned to pass through the hole into the room. These rays form the image.

The size of the hole in the camera obscura is important. Too big a hole makes a blurry image. Too small a hole makes a sharp image that can be dim and difficult to see. In the 16th century, Italian scholars noted that a lens placed in the hole of a camera obscura produces a bright, sharp image on a viewing screen held the right distance from the lens.