BLACK AND WHITE NEGATIVE FILM PROCESSING [Film Technology]

BLACK AND WHITE NEGATIVE FILM PROCESSING 
[Film Technology]

The latent image in negative will not be visible. This will be subjected to chemical changes with the help of some chemical changes. Then the exposed silver halide molecules will change to black coloured metallic silver molecules. Unexposed molecules will continue as unchanged. Then the metallic silver molecules will be diluted and the unexposed silver halide molecules will apart from the emulsion. In the fixing stage of processing the metallic silver molecules will be fixed in the emulsion. After bleach, wash and film drying the processing is completed and a negative image will be obtained in the film.

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BLACK AND WHITE FILM DEVELOPING [Film Technology]

BLACK AND WHITE FILM DEVELOPING 
[Film Technology]

The process of image formation can be much amplified by the use of a developing agent. This is a chemical reducing agent that act as donating electrons to positively charged silver ions in the emulsion and converting them to metallic silver. This reaction takes place most rapidly around the tiny particles of silver in development centres that have already formed during exposure. The silver may be thought of as acting as a catalyst for the reaction, and exposed crystals are developed up to two hundred times faster than unexposed ones. The reaction of development may be as Ag⁺br^-₊(dev)->Ag₊(dev)⁺+Br^- The initial developing agent and silver bromide react to produce grains of metallic silver which, being insoluble, remain in the film emulsion, and oxidized developing agent and bromide ions, both which pass into solution. Thus the exposed areas of the film are visibly darkened by the formation of metallic silver. The image can be made permanent by passing the film into a fixer solution, which dissolves away the unwanted silver bromide.

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BLACK AND WHITE FILM EMULSION [Film Technology]

BLACK AND WHITE FILM EMULSION 
[Film Technology]

A chemical compound sensitive to light applied on the black and white film. It is a gelatin layer consists of  silver bromide or silver iodide known as halides. While expose as a result of a chemical change the image will be obtained. This image is called latent image because it is not visible. When develop the film with special type of chemicals the molecules holding latent image will become black coloured metallic silver. The exposed regions will not change. In developed film the image will be visible.

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BIREFRINGENCE EFFECT [Film Technology]

BIREFRINGENCE EFFECT
[Film Technology]

It is possible at  an appreciable light loss, to obtain coloured patterns of changing hues (birefringence effect). A slide is made with designs in mica, quartz, plastic sheeting or tape. This is sandwiched between two sheets of Polaroid filter. As one of the filters is rotated, colours vary.

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