Photo

A photograph (often shortened to photo) is an image created by light falling on a light-sensitive surface, usually photographic film or an electronic imager such as a CCD or a CMOS chip. more...

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Most photographs are created using a camera, which uses a lens to focus the scene's visible wavelengths of light into a reproduction of what the human eye would see. The process of creating photographs is called photography.

Motion pictures, such as film or video, are generally considered to be sequences of photographs.

History

The first permanent photograph was made in 1826 by a French inventor, Joseph Nicéphore Niépce, building on a discovery by Johann Heinrich Schultz (1724): that a silver and chalk mixture darkens under exposure to light. Niépce and Louis Daguerre refined this process. Daguerre discovered that exposing the silver first to iodine vapor, before exposure to light, and then to mercury fumes after the photograph was taken, could form a latent image; bathing the plate in a salt bath then fixes the image. These ideas led to the famous daguerreotype.

The daguerreotype had its problems, notably the extreme fragility of the resulting picture, and that it was a positive-only process and thus could not be re-printed. Inventors set about looking for improved processes that would be more practical. Several processes were introduced and used for a short time between Niépce's first image and the introduction of the collodion process in 1848. Collodion-based wet-glass plate negatives with prints made on albumen paper remained the preferred photographic method for some time, even after the introduction of the even more practical gelatin process in 1871. Adaptations of the gelatin process have remained the primary black-and-white photographic process to this day, differing primarily in the film material itself, originally glass and then a variety of flexible films.

Color photography is almost as old as black-and-white, with early experiments dating to John Herschel's experiments with Anthotype from 1842, and Lippmann plate from 1891. Color photography became much more popular with the introduction of Autochrome Lumière in 1903, which was replaced by Kodachrome, Ilfochrome and similar processes. For many years these processes were used almost exclusively for transparencies (in slide projectors and similar devices), but color prints became popular with the introduction of the Chromogenic negative, which is the most-used system in the C-41 process. The needs of the movie industry have also introduced a host of special-purpose systems, perhaps the most well known being the now-rare Technicolor.

Types of photographs

Non-digital photographs are produced with a two-step chemical process. In the two-step process the film holds a negative image (colors and lights/darks are inverted), which is then transferred onto photographic paper as a positive image. Another widely used film is the positive film used for producing transparencies, usually mounted in cardboard or plastic frames called slides. Slides are widely used by professionals due to their sharpness and accuracy of color rendition. Most photographs published in magazines are taken on color transparency film.

Read more at Wikipedia.org