What is the silver salt process in photography?

Traditional photography is to let the external light pass through the lens to form a clear image in a closed camera and fall on the film. After exposure, the film converts these images into latent images of silver halide.

The main photosensitive substance on the film is silver halide, which will change when exposed to light. When the film is developed in a darkroom and the silver halide is bleached, the silver particles remain on the film.

When the film is illuminated, the silver particles are relatively dense, the silver particles are relatively sparse where there is little illumination, and there are no silver particles where there is no illumination. The density of silver particles on the film is called the density of the film.

It's just that these silver particles on the film are tiny metallic silver in black, not shiny silver that is common in daily life. The image on the black-and-white photo is formed by darkroom printing and enlarging the negative composed of these "expensive black metal particles".

Extended data

Because of the different composition of silver halide, the photosensitive sensitivity of emulsion is different, and the order of photosensitive speed is-the emulsion containing a small amount of silver iodide in silver bromide has the fastest photosensitive speed, followed by silver bromide and silver chloride is the slowest.

According to these characteristics, generally speaking, negative emulsion contains silver bromide and a small amount of silver iodide, while silver chloride is only suitable for low-speed positive emulsion. The diameter of silver halide crystal particles varies from 20 to 50 microns to 50 nanometers, and most of them are 0. 1 to 4 microns.

According to its type, shape, size and distribution, the properties of photosensitive materials, such as photosensitive speed, resolution and contrast, are largely determined. For example, silver chloride is usually used to obtain finer particles, higher contrast, or make the image tone tend to brown-black.

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