What is the silver salt process in photography

Traditional photography is through the lens, so that the external light in the closed camera to form a clear image falls on the film, the film after exposure, the conversion of these images into silver halide latent image.

The main light-sensitive material on the film is silver halide, which changes when it encounters light. When the film is developed in the darkroom to bleach out the silver halide, silver particles remain on the film.

Exposure of the film to see more light, silver particles on the more dense, less light, silver particles on the more sparse, and no light on the place of no silver particles, silver particles on the film on the degree of density known as the density of the film.

Only these silver particles on the film is black, fine metallic silver, not like the common daily life of the kind of shiny silver. The image on a black-and-white photograph is formed from these "expensive black metal particles" on the negative by the printing and enlarging process in the darkroom.

Expanded

Photographic emulsions in the silver halide composition is different, the sensitivity is different, according to the speed of light-sensitive order is - silver bromide in the addition of trace amounts of silver iodide in the emulsion light-sensitive the fastest, silver bromide, the second, the slowest silver chloride.

Based on these characteristics, generally speaking, negative emulsions contain silver bromide and a small amount of silver iodide, while silver chloride is only suitable for low-speed positive emulsions. Silver halide crystal particles range in diameter from 20 to 50 microns to 50 nanometers, with most having a diameter size of 0.1 to 4 microns.

Depending on its type, form, size and distribution, it largely determines the performance of the photographic material, such as the speed of sensitization, resolution, contrast and so on. For example, silver chloride is often used to get finer particles, higher contrast, or to make the image hue brownish-black.

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