Prince Alfred, Duke of Edinburgh, c 1870.

UNITED KINGDOM - AUGUST 06: A carte-de-visite portrait of Prince Alfred (1844-1900), the Duke of Edinburgh, taken at the studio of Levitsky, Paris, France, in about 1870. A carte-de-visite is a photograph mounted on a piece of card the size of a formal visiting card of the 1850s - hence the name. The format was introduced by the French photographer Andre-Adolphe-Eugene Disderi (1819-1889) in 1854. As well as family portraits, commercial cartes of celebrities such as politicians, royalty and popular personalities were published. The craze for collecting celebrity cartes-de-visite in albums reached its peak during the 1860s but the format remained popular until the beginning of the twentieth century. The backs of cartes-de-visite were normally printed with the photographer's name and address. (Photo by SSPL/Getty Images)