This daguerreotype of the actress and writer Johanne Luise Heiberg (1812–90) was made by Carl Gustav Oehme (1817–81), probably in 1854 or 1855, when Heiberg was visiting the German spas. Oehme ran the largest photographic studio in Berlin and had learned the daguerreotype process in Paris from its inventor, Louis-Jacques-Mandé Daguerre (1787–1851). After years of experimentation, in the late 1830s Daguerre succeeded in capturing images by exposing a silver-plated copper sheet to the vapor given off by iodine crystals. The earliest daguerreotypes generally were portraits and, unlike later photographs that could be reproduced from negatives, each daguerreotype is unique. The Danes were quick to adopt the new technique and several Danish-made daguerreotypes from the 1840s exist. The Royal Library holds one of the largest collections of daguerreotypes in Scandinavia. Heiberg was one of the most important Danish actresses of the 19th century, best known for the many roles she played at the Royal Theater in Copenhagen.