A pinhole camera is the most basic type of camera, made up of a light-proof container (usually a box) with a tiny hole in the one side (hence the term "pinhole"). Film or photographic paper is placed on the inside of the box, opposite the hole. Light enters through the hole and creates an inverted image on the film.
Natural Pinhole Cameras
Images created in the same manner as a pinhole camera occur naturally. Descriptions of these types of images have been recorded for centuries. Mo Ti, a fifth century B.C.E. Chinese philosopher, observed them, as did Aristotle. Tenth-century Islamic astronomer, mathematician, and physicist Ibn al-Haitham observed such images, and through his observations discovered that it is light entering the eyes that causes us to see.
First Constructed Cameras
Al-Haitham is also credited with inventing the first pinhole camera. Observing how light entered the room through a hole in his shutters, he experimented with light and aperture until he could reproduce the effect. The first detailed description of a pinhole camera was made by Leonardo da Vinci, who wrote in the Codex Atlanticus about the pinhole camera he used to study perspective. The first actual photograph with a pinhole camera was taken in 1850 by Scottish scientist Sir David Brewster.
Pinhole cameras work on the concept of rectilinear propagation of light (rectilinear meaning moving in a straight line). This describes the movement of light rays, which bounce off the camera's subject, and are filtered by the hole. The rays create an image, and not a point of light, because they enter the hole at varying angles. Rays coming upward from the bottom of an object pass through the hole and toward the top of the box. Those coming down from the top of the object go toward the bottom of the box. This is why the image projected on the inside of the camera is inverted.
The size of the hole affects the focus of the photo taken. If the hole is too large, superfluous light coming through the hole will cause the picture to be out of focus. If the hole is too small, the rays will be diffracted, and the picture will also be out of focus. The best size for the hole in a pinhole camera can actually be calculated by a formula perfected by Lord Rayleigh, British Nobel Prize winner, and published in his book "Nature" in 1891.
Pinhole cameras are still in use today, despite the ample availability of highly advanced photographic equipment. While images are hard to enlarge, susceptible to chromatic aberrations, and less sharp than those from a camera with a lens, they have an incredible depth of field. A photographer using a pinhole camera adjusts exposure manually, and can take advantage of the limited settings to induce creativity in lighting, subject choice, and composition in her photographs.