Elements of the photographic process have been around for centuries. For example, lenses are first mentioned in one of Aristophanes' plays (dating from 434 BC), and the principle of the camera obscura has been known for a thousand years.
An example of the camera obscura is that bright sunlight, passing through a pinhole into a darkened room, will cast a reflection of the scene outside the room on to the wall opposite the hole. The portable camera obscura became popular during the seventeenth and eighteenth centuries, when it was used by architects and artists for tracing the outlines of buildings, landscapes and still life. During the seventeenth century, a simple convex lens was introduced in place of the pinhole and this created a bright clear image on the focusing screen.
In 1725 Johanne Heinrich Schulze, a German professor of anatomy, demonstrated how light rays affected certain chemicals by exposing salts of silver to the sun. By 1802 scientists Thomas Wedgewood and Sir Humphrey Davy had combined this with the camera obscura, but were unable to fix the images to make them permanent.
A Frenchman, Nicephore Niepce, discovered a process in 1826 for fixing and making permanent the captured image and subsequently made the world's first photograph. Although the exposure of this very rough image took almost eight hours, the fixing process was so successful that these images can still be viewed today. Niepce died in 1833 but his partner, Louis Jacques Mande Daguerre, continued experiments and in 1839 he introduced the world's first commercial photographic process the 'Daguerrotype'. This was a much faster process, turning exposure times from hours into minutes.