A platinum print or platinotype is a photographic print made by a printing process which leaves platinum metal on the surface of the paper. Platinum prints are noted for their large tonal range and for being highly stable.
Unlike the gelatin silver process, in which silver is held in a gelatin emulsion that coats the paper, platinum metal is left directly on the paper's surface or absorbed into the media. As a result, a platinum image is absolutely matte.
In photography, toning is a method of altering the color of black-and-white photographs. In analog photography, it is a chemical process carried out on metal salt-based prints, such as silver prints, iron-based prints (cyanotype or Van Dyke brown), or platinum or palladium prints. This darkroom process cannot be performed with a color photograph. The effects of this process can be emulated with software in digital photography. Sepia is considered a form of black-and-white or monochrome photography.
View the full Wikipedia page for Sepia tone