camera

History
The forerunner to the photographic camera was the camera obscura,a
Latin name literally meaning a dark room but more generally "...a
darkened chamber or box, into which light is admitted through a
pinhole (later a convex lens), forming an image of external objects on a
surface of paper or glass, etc., placed at the focus of the lens". In the
6th century, Greek mathematician and architect Anthemius of Tralles
used a type of camera obscura in his experiments. The camera obscura
was described by the Arabic scientist Ibn al-Haytham (Alhazen) in his
Book of Optics (1015–1021). Scientist-monk Roger Bacon also studied
the matter. The actual name of camera obscura was applied by
mathematician and astronomer Johannes Kepler in his Ad Vitellionem
paralipomena of 1604. He later added a lens and made the apparatus
transportable, in the form of a tent. British scientist Robert Boyle and
his assistant Robert Hooke developed a portable camera obscura in
the 1660s.
The first camera obscura that was small enough for practical use as a
portable drawing aid was built by Johann Zahn in 1685.At that time
there was no way to preserve the images produced by such cameras
except by manually tracing them. However, it had long been known that
various substances were bleached or darkened or otherwise changed
by exposure to light. Seeing the magical miniature pictures that light
temporarily "painted" on the screen of a small camera obscura inspired
several experimenters to search for some way of automatically making
highly detailed permanent copies of them by means of some such
substance
Early photographic cameras were usually in the form of a pair of nested
boxes, the end of one carrying the lens and the end of the other
carrying a removable ground glass focusing screen. By sliding them
closer together or farther apart, objects at various distances could be
brought to the sharpest focus as desired. After a satisfactory image had
been focused on the screen, the lens was covered and the screen was
replaced with the light-sensitive material. The lens was then uncovered
and the exposure continued for the required time, which for early
experimental materials could be several hours or even days. The first
permanent photograph of a camera image was made in 1826 by Joseph
Nicéphore Niépce using a sliding wooden box camera made by Charles
and Vincent Chevalier in Paris.
Similar cameras were used for exposing the silver-surfaced copper
Daguerreotype plates, commercially introduced in 1839, which were the
first practical photographic medium. The collodion wet plate process
that gradually replaced the Daguerreotype during the 1850s required
photographers to coat and sensitize thin glass or iron plates shortly
before use and expose them in the camera while still wet. Early wet
plate cameras were very simple and little different from Daguerreotype
cameras, but more sophisticated designs eventually appeared. The
Dubroni of 1864 allowed the sensitizing and developing of the plates to
be carried out inside the camera itself rather than in a separate
darkroom. Other cameras were fitted with multiple lenses for
photographing several small portraits on a single larger plate, useful
when making cartes de visite. It was during the wet plate era that the
use of bellows for focusing became widespread, making the bulkier
and less easily adjusted nested box design obsolete.
For many years, exposure times were long enough that the
photographer simply removed the lens cap, counted off the number of
seconds (or minutes) estimated to be required by the lighting
conditions, then replaced the cap. As more sensitive photographic
materials became available, cameras began to incorporate mechanical
shutter mechanisms that allowed very short and accurately timed
exposures to be made.
The electronic video camera tube was invented in the 1920s, starting a
line of development that eventually resulted in digital cameras, which
largely supplanted film cameras after the turn of the 21st century.