Silver halide

Silver halides are light-sensitive compounds of silver and halogens, especially silver bromide, silver chloride, and silver iodide. In photographic emulsions, exposure creates latent images that chemical development turns into visible photographs.

Latent image: An invisible pattern of exposure-induced changes in a photosensitive material that can be made visible by development. Exposed silver-halide crystals preserve the image before any visible silver forms.
Silver chloride: A silver halide with the formula AgCl, used in photographic materials and other applications. It is generally less sensitive to light than silver bromide and suits different photographic uses.
Johann Heinrich Schulze: A German professor whose eighteenth-century experiments showed that light darkens silver compounds. His demonstrations established that light, rather than heat, could produce photographic darkening.
Gelatin silver print: A photographic print made by developing metallic silver in a gelatin-coated paper layer. It is a durable, widely used print form based on developed silver-halide emulsions.
Digital photography: Image capture and storage using electronic sensors and digital data rather than a chemical photographic image. It records light electronically instead of forming an image through silver-halide exposure and processing.
Photographic development: A chemical process that converts exposed regions of a photographic material into a visible image. Developer reduces image-bearing silver-halide crystals to metallic silver.
Silver iodide: A silver halide with the formula AgI, notable for its use in photographic emulsions and cloud seeding. Its crystal properties and photosensitivity distinguish it from the other common emulsion halides.
Thomas Wedgwood: An English experimenter who made early camera images on light-sensitive surfaces but could not fix them permanently. His attempts used silver compounds to capture images before practical fixing was available.
Photographic film: A flexible strip or sheet coated with a light-sensitive emulsion for recording images. Its emulsion stores exposure patterns in silver-halide crystals until processing.
Cyanotype: An iron-based photographic printing process that produces images in characteristic blue tones. It is a light-sensitive photographic process that does not rely on silver halides.

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