Photography

Photography is the result of combining several technical discoveries. Long before the first photographs were made, Chinese philosopher Mo Didescribed a pinhole camera in the 5th century B.C.E.,^[4] Ibn al-Haytham (Alhazen) (965–1040) studied the camera obscura and pinhole camera,^[4][5]Albertus Magnus (1193–1280) discovered silver nitrate,^[6] and Georges Fabricius (1516–1571) discovered silver chloride.^{[citation needed]} Daniel Barbaro described a diaphragm in 1568.^{[citation needed]} Wilhelm Homberg described how light darkened some chemicals (photochemical effect) in 1694.^{[citation needed]} The fiction book Giphantie, published in 1760, by French author Tiphaigne de la Roche, described what can be interpreted as photography.^{[citation needed]}

Invented in the first decades of the nineteenth century, photography (by way of the camera) seemed able to capture more detail and information than traditional mediums, such as painting and sculpting.^[7] Photography as a usable process goes back to the 1820s with the development of chemical photography. The first permanent photoetching was an image produced in 1822^[3] by the French inventor Nicéphore Niépce, but it was destroyed by a later attempt to duplicate it.^[3] Niépce was successful again in 1825. He made the first permanent photograph from nature with a camera obscura in 1826. However, because his photographs took so long to expose (8 hours), he sought to find a new process. Working in conjunction with Louis Daguerre, they experimented with silver compounds based on a Johann Heinrich Schultz discovery in 1724 that a silver and chalk mixture darkens when exposed to light. Niépce died in 1833, but Daguerre continued the work, eventually culminating with the development of the daguerreotype in 1837. Daguerre took the first ever photo of a person in 1839 when, while taking a daguerreotype of a Paris street, a pedestrian stopped for a shoe shine, long enough to be captured by the long exposure (several minutes). Eventually, France agreed to pay Daguerre a pension for his formula, in exchange for his promise to announce his discovery to the world as the gift of France, which he did in 1839.

Mid 19th century "Brady stand" photo model's armrest table, meant to keep portrait models more still during long exposure times (studio equipment nicknamed after the famed US photographer, Mathew Brady).

Meanwhile, Hercules Florence had already created a very similar process in 1832, naming it Photographie, and William Fox Talbot had earlier discovered another means to fix a silver process image but had kept it secret. After reading about Daguerre's invention, Talbot refined his process so that portraits were made readily available to the masses. By 1840, Talbot had invented the calotype process, which creates negative images.John Herschel made many contributions to the new methods. He invented the cyanotype process, now familiar as the "blueprint". He was the first to use the terms "photography", "negative" and "positive". He discovered sodium thiosulphate solution to be a solvent of silver halides in 1819, and informed Talbot and Daguerre of his discovery in 1839 that it could be used to "fix" pictures and make them permanent. He made the first glass negative in late 1839.

In March 1851, Frederick Scott Archer published his findings in "The Chemist" on the wet plate collodion process. This became the most widely used process between 1852 and the late 1880s when the dry plate was introduced. There are three subsets to the Collodion process; theAmbrotype (positive image on glass), the Ferrotype or Tintype (positive image on metal) and the negative which was printed on Albumen or Salt paper.

Many advances in photographic glass plates and printing were made in through the nineteenth century. In 1884, George Eastman developed the technology of film to replace photographic plates, leading to the technology used by film cameras today.

In 1908 Gabriel Lippmann won the Nobel Laureate in Physics for his method of reproducing colors photographically based on the phenomenon of interference, also known as the Lippmann plate.

Control	Description
Focus	The adjustment to place the sharpest focus where it is desired on the subject.
Aperture	Adjustment of the lens opening, measured as f-number, which controls the amount of light passing through the lens. Aperture also has an effect on depth of field and diffraction – the higher the f-number, the smaller the opening, the less light, the greater the depth of field, and the more the diffraction blur. The focal length divided by the f-number gives the effective aperture diameter.
Shutter speed	Adjustment of the speed (often expressed either as fractions of seconds or as an angle, with mechanical shutters) of the shutter to control the amount of time during which the imaging medium is exposed to light for each exposure. Shutter speed may be used to control the amount of light striking the image plane; 'faster' shutter speeds (that is, those of shorter duration) decrease both the amount of light and the amount of image blurring from motion of the subject and/or camera.
White balance	On digital cameras, electronic compensation for the color temperature associated with a given set of lighting conditions, ensuring that white light is registered as such on the imaging chip and therefore that the colors in the frame will appear natural. On mechanical, film-based cameras, this function is served by the operator's choice of film stock or with color correction filters. In addition to using white balance to register natural coloration of the image, photographers may employ white balance to aesthetic end, for example white balancing to a blue object in order to obtain a warm color temperature.
Metering	Measurement of exposure so that highlights and shadows are exposed according to the photographer's wishes. Many modern cameras meter and set exposure automatically. Before automatic exposure, correct exposure was accomplished with the use of a separate light metering device or by the photographer's knowledge and experience of gauging correct settings. To translate the amount of light into a usable aperture and shutter speed, the meter needs to adjust for the sensitivity of the film or sensor to light. This is done by setting the "film speed" or ISO sensitivity into the meter.
ISO speed	Traditionally used to "tell the camera" the film speed of the selected film on film cameras, ISO speeds are employed on modern digital cameras as an indication of the system's gain from light to numerical output and to control the automatic exposure system. The higher the ISO number the greater the film sensitivity to light, whereas with a lower ISO number, the film is less sensitive to light. A correct combination of ISO speed, aperture, and shutter speed leads to an image that is neither too dark nor too light, hence it is 'correctly exposed,' indicated by a centered meter.
Autofocuspoint	On some cameras, the selection of a point in the imaging frame upon which the auto-focus system will attempt to focus. ManySingle-lens reflex cameras (SLR) feature multiple auto-focus points in the viewfinder.