A photograph (often just called a photo) is an image (or a representation of that on e.g. paper) created by collecting and focusing reflected electromagnetic radiation. The most common photographs are those created of reflected visible wavelengths, producing permanent records of what the human eye can see.
Most photographs are made with a camera, which focuses the light onto either photographic film or a CCD or CMOS image sensor . Photographs can also be made by placing objects on photosensitive paper and exposing it to light (the result is often called a photogram) or by placing objects on the platen of a flatbed scanner (see scanner art).
History and special effects
Most traditional photographs are produced with a two-step chemical process. In the two-step process, the film holds a negative image (colours 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 mostly due to their sharpness and accuracy of colour rendition. Most photographs published in magazines are still originally taken on colour transparency film. One of the most famous transparency films is Kodachrome.
Originally almost all photographs were black and white. Although methods for developing color photos were available as early as the late 19th century, they did not become widely available until the 1940s or 50s, and even in until the 1960s most photographs were taken in black and white. Since then, colour photography has dominated popular photography, although the black and white format remains popular for amateur photographers and artists. Black and white film is considerably easier to develop than colour.
Panoramic format images can be taken by using special cameras like the Hasselblad Xpan on standard film. Since the 1990s panoramic photos have been relatively easy for the general population to take on Advanced Photo System film. APS was developed by several of the major film manufacturers to provide a "smart" film with different formats and computerized options available. With the advent of digital photography this format has become less popular and will be discontinued in the near future.
Digital photos can be stored in various file formats, of which JPEG is the most popular. Many other graphic formats are used, including TIFF, PNG, GIF, and RAW.
Some photographs are forbidden, e.g. representing child pornography and those that are considered espionage.
Last updated: 08-17-2005 00:12:18