n. One who or that which develops or unfolds.n. Specifically, in photography, the chemical bath in which a sensitized plate or paper is, after a photographic exposure to the light, immersed to develop or bring out the latent image. Developers for the ordinary dry-plate process may be divided into two principal classes, alkaline developers and ferrous-oxalate developers, the first generally employing carbonate of soda or potash in combination with pyrogallic acid, and the second using oxalate of potash with protosulphate of iron. The results obtained are practically the same with either bath, the latent image in the film being made visible, and the chemical changes induced being fixed, or made permanent in the fixing bath, which follows the developing bath. Many other chemicals may be used in development, either in combination with some of those mentioned above or in independent combinations. See photography.