The simplest and most likely oldest optical device used to generate an image of an object is the pinhole camera. The famous Greek philosopher and naturalist Aristotle first described the construction and operation of a “dark chamber” over 2000 years ago. In this dark chamber, a small opening was made for light to pass through (in Latin: a camera obscura). With this, Aristotle unknowingly discovered the basic principle of photography.
When light enters a small hole into an opaque hollow container, an upside-down image is generated on the back surface. When the surface on which the image appears is made of transparent material, the image can be viewed from outside of the container.
The sharpness and brightness of an image produced by a pinhole camera is solely determined by the diameter of the hole allowing light to pass through. Exposure times range anywhere from five seconds to several hours.
Compared to cameras capable of focusing, the luminosity of pinhole cameras is 10 to 500 times weaker and the image is noticeably fuzzier. The image produced can be captured with the help of light-sensitive material(s) or an image sensor.
Starting at the end of the 13th century, astronomers began using the camera obscura for observing solar eclipses and other astronomic phenomena. This helped them observe the eclipse without damaging their eyes by looking directly into the bright sunlight. Walk-in camera obscuras were built for such observations and can still be found in some places today.
Pinholes are also used in the fields of X-ray and gamma radiation to produce corresponding images since no traditional lenses can be used for this purpose. Complex or large-sized versions are equipped with converging lenses.
Pinhole cameras made with wooden or plastic housings can be purchased starting at around 30 Euros while simpler models made of cardboard are even cheaper. Because the simple principle of a pinhole camera is easy to craft with simple materials, there are numerous tutorials and craft kits available for purchase on the Internet that will help you create your very own camera obscura.
Even digital cameras with interchangeable lenses or SLR cameras can be used as a pinhole camera. For this purpose, some manufacturers (such as Nikon) offer special lenses.