No single figure can be credited with the invention of the silver gelatin photographic process,
which gradually became the most important photographic printing process of the twentieth
century. Several inventors, including Peter Mawdsley, Josef Marie Eder, Giuseppe Pizzighelli, and
Sir William de Wiveleslie Abney, can be credited with the most important contributions to its
development and research of several key types of silver halide gelatin emulsions. The development
of the baryta layer, even when not directly related to silver gelatin photography, goes back to its
introduction by José Martinez-Sanchez and Jean Laurent in 1866.
A silver gelatin print by Henri Cartier-Bresson appears in figure 1. Figure 2 shows a historical
timeline of the silver gelatin photographic process.
Silver gelatin photographic papers were available both as POP (printing-out paper) and as DOP
(developing-out paper). Even though the internal chemical structure of both types is very similar,
the handling and processing of each was quite different, and it is best to describe them separately