pinhole camera

A pinhole camera is a simple camera that uses a small hole, or pinhole, instead of a lens to form an image. Light rays from an object pass through this pinhole and project an inverted image onto a screen or film. The quality of the image depends on the size of the pinhole. If the hole is too large, the image will be blurred because each point in the object is projected as a patch of light. If the hole is too small, diffraction effects cause the image to blur. The optimal pinhole size balances these two effects, typically occurring when the diameter is approximately the square root of twice the wavelength of light times the distance between the pinhole and the film. This concept is a fundamental example in understanding how images are formed in optics.1