![]() ![]() ![]() This negative image is composed of metallic silver formed in the first developer step. Following the first developer and rinse, the film is bleached to remove the developed negative image.This process has three additional stages: The film is then fixed by converting all remaining silver halide into soluble silver complexes. Exposed silver halide oxidizes the hydroquinone, which then oxidizes a nucleating agent in the film, which is attacked by a hydroxide ion and converts it via hydrolysis into a nucleating agent for silver metal, which it then forms on unexposed silver halide, creating a silver image. In graphic art film, which is a special type of black and white film used for converting images into halftone images for offset printing, a developer containing methol-hydroquinone and sulfite stabilizers may be used. An example of a black and white developer is Kodak D-76 which has bis(4-hydroxy-N-methylanilinium) sulfate with hydroquinone and sodium sulfite. It is then fixed by converting all remaining silver halide into a soluble silver complex, which is then washed away with water. Two examples of enlargement techniques are dodging and burning.Īlternatively (or as well), the negative may be scanned for digital printing or web viewing after adjustment, retouching, and/or manipulation.įrom a chemical standpoint, conventional black and white negative film is processed by a developer that reduces silver halide to silver metal, exposed silver halide is reduced faster than unexposed silver halide, which leaves a silver metal image. Many different techniques can be used during the enlargement process. The negative may now be printed the negative is placed in an enlarger and projected onto a sheet of photographic paper. Once the film is processed, it is then referred to as a negative. Film is then dried in a dust-free environment, cut and placed into protective sleeves.(In very hard water areas, a pre-rinse in distilled water may be required – otherwise the final rinse wetting agent can cause residual ionic calcium on the film to drop out of solution, causing spotting on the negative.) Film may be rinsed in a dilute solution of a non-ionic wetting agent to assist uniform drying, which eliminates drying marks caused by hard water.The washing time can be reduced and the fixer more completely removed if a hypo clearing agent is used after the fixer. Residual fixer can corrode the silver image, leading to discolouration, staining and fading. Washing in clean water removes any remaining fixer.A common fixer is hypo, specifically ammonium thiosulfate. The fixer makes the image permanent and light-resistant by dissolving remaining silver halide.A rinse with clean water may be substituted. A stop bath, typically a dilute solution of acetic acid or citric acid, halts the action of the developer.The developer converts the latent image to macroscopic particles of metallic silver.The film may be soaked in water to swell the gelatin layer, facilitating the action of the subsequent chemical treatments.Photographic processing transforms the latent image into a visible image, makes this permanent and renders it insensitive to light. Black and white negative processing is the chemical means by which photographic film and paper is treated after photographic exposure to produce a negative or positive image. ![]()
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