Wiki #27: Photographic Film

Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts, that are bound by gelatin. The size of the silver halide salt crystals can vary, reulting in different senstivities, resolutions, and contrast for in film. Different levels of sensitivity, resolution, and contrast allow photographers to use different film to achieve a desired "look" in their photgraphs. When light hits the film the silver crystals form a latent, or invisible, image which is later made visible through chemicals used in processing, The chemicals turn the silver crsytals into metalic silver, in black and white photography, resulting in a negative image. It is a negative image because the places where light hit the film appear darkest and black, while the places where no light reached remain light, resulting in the opposite of the original imagae. The image is then made positive when light is shone through the developed film onto light sensitive paper, whish also contains silver halide salt crystals. The reversed light shone through the film then creates a positive latent image, which is then prossessed and becomes a photograph.