The dispersion of light through a small aperture to produce an image is a phenomenon which has been observed for a very long time, probably before the dawn of history. It manifests itself in nature during a solar eclipse, when the reduced light levels permit the image of the eclipsed sun to be visibly projected through the tiny spaces between the leaves of a tree as multiple pictures of the solar corona on the ground.
A small aperture such as a pinhole will project an image onto a surface by the diffraction of light without a lens. This image usually goes unnoticed because the image is very faint and is overwhelmed by the ambient light levels. However, if one were to enclose oneself in a dark room (a camera obscura), the image would become very visible as the eyes grow accustomed to the low light levels. This phenomenon was discovered and used in the Renaissance as an aid to accurate perspective drawing. The addition of a lens further enhanced the sharpness and brightness of the image. The invention of photographic coatings in the 19th Century allowed the image to be captured permanently, and photography was born.
A photograph produced by a pinhole camera is equally sharp, whether the image is near or far from the camera. Generally speaking, the smaller the pinhole, the sharper the image is. Since the pinhole produces a very wide-angle image (about 140 degrees), the closer the film is to the pinhole, the wider the image appears, because the entire image circle is being captured. Increasing the distance between the film and pinhole results in a smaller part of the image being captured, and hence appears like a “telephoto” image.
Because the image is so faint, long exposure times are required, from several seconds to many hours and longer, even days or weeks in extreme circumstances. The interior of a building may require a half-hour to expose, which means that people moving through the view do not register on the film unless they hold perfectly still during the exposure. For this reason, a pinhole picture taken of a crowded space will appear to be empty if people are moving through it.
It is very interesting to devise different designs for pinhole cameras, and many intriguing variations have been done, such as multiple-pinhole, panoramic and countless surprising apparati of great ingenuity. The cameras may be as simple as an oatmeal container, may be elaborately crafted from durable materials such as metal and wood, or may even make use of an entire room or vehicle. Images produced by these cameras do not look like modern photographs. They have a softer, still quality like the photographs from the past.
For images of pinhole cameras and and their design sketches, see images at the end of the gallery photos.