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3. Fixing the image. Unexposed AgX on the photography film is removed with thiosulfate (eq. 3). The soluble complex, [Ag(S O 2-] 3-, can be easily washed away to leave only the silver image.
The process above forms the negative in black-and-white photography; light shining through the negative produces the final photograph (the positive).
4.Toning (coloring) the image. The silver-based black and white photographs may be
altered, to produce different colored images. Ex. Ag with thiosulfate in acid solution produces sulfur that then reacts with the Ag-image to yield the brown Ag2S which creates sepia photographs.
Light
The silver halides located on the film are sensitive to:
2. Development. The small number of Ag metal atoms formed act as a catalyst and sensitizes the surrounding halide salt so the sensitized AgX is reduced, to produce black silver metal in the area exposed to light. Modern developers contain one of many reducing agents. The most common is hydroquinone, which reacts with Ag+ (in AgX).
Developer:"A solution for developing a film or photographic paper - i.e. for turning an exposed film's or paper's latent image into an image that can be seen"
Fixer:"The chemical solution used for fixation. It removes any photo-sensitive silver-halide crystals that were not acted upon by light or by the developer"
Collodion: "a colourless or yellow syrupy liquid that consists of a solution of pyroxylin in ether and alcohol: used in medicine and in the manufacture of photographic plates, lacquers, etc"
The methods created by Daguerre and Talbot were inconvenient because they required a long time of exposure, could be as long as 60 minutes. In 1840 Talbot improved by having a short exposure that left an invisible "latent" on the film. This could be developed into a visible image by treating it with a solution of Gallic acid and silver nitrate. The main difference between Talbot's method and the method existing today is the silver halide which is suspended in gelatin.
"1. Forming the image by exposure to light : A small number of X- ions in the AgX crystals that are located in the film are oxidized to form X. The electrons that are released from this oxidation reaction reduces the Ag+ to silver metal in the surrounding AgX crystal."
1. Exposure of the film in the camera
2. Development of the negative image
3. Dissolution of the developed silver image by treatment with an oxidizing agent
4. Exposure of the remaining silver halide to light or to a chemical fogging agent
5. Development of the silver halide, producing a positive image
6. Washing and drying of the film.
http://chemistryexplained.com
http://www.idc-online.com/technical_references/pdfs/mechanical_engineering/photographys01.pdf
http://www.chemistryexplained.com/Ny-Pi/Photography.html#ixzz3ZHSgrMpe
http://science.howstuffworks.com/innovation/everyday-innovations/instant-film.htm
http://www.sprawls.org/ppmi2/FILMSEN/#SENSITIVITY
http://www.idc-online.com/technical_references/pdfs/mechanical_engineering/photographys01.pdf
https://terpconnect.umd.edu/~Toh/ChemConference/ChemConf96/Bodner/Paper2.html
http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/photchem.htm
http://www.photographytips.com/page.cfm/2011
1. Exposure of the sensitive material, usually a gelatin emulsion of silver halides on a cellulose acetate film, in the camera
2. Development in the darkroom by treating the film with a solution of organic reducing agents such as hydroquinone and N-methyl paraaminophenol. The reagents reduce to metallic silver those silver halide crystals that acquired latent-image silver clusters. The brighter the subject of a photograph, the darker is the image that forms in this development, so that one obtains a negative picture.
3."Fixing" the image so that the film will not darken on further exposure to light. This is accomplished by dissolving the undeveloped silver halide grains in a solution of sodium thiosulfate:
4. Washing away the dissolved silver salts and drying the negative.
5. Printing, that is, shining diffuse light through the negative onto a sheet of sensitive photographic paper (a gelatin emulsion on paper).
6. Darkroom development of the exposed paper using developer solution much like that used in the film development step. This step produces a positive image, in which the tones are like those in the original scene.
7. Fixing, washing, and drying the print as in the analogous film processing steps.