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Throughout his career, Murray used paper negatives and the calotype process - a technique of creating "positive" prints from one negative - to produce his images.

Biggs experimented with the calotype process, producing "positive" prints from one negative.

Fox Talbot's image of the cat was made by creating "positive" prints from one negative - a technique he called the calotype process, after the Greek word "kalos", meaning beauty.

Daguerreotypes were unique artefacts; Talbot’s calotype was a paper negative that could yield any number of positive copies.

Polymath William Henry Fox Talbot began the history of British photography with the invention of his "calotype" process, patented in February 1841.