A candid photograph is a photograph captured without creating a posed appearance. This is achieved in many ways, for example:
Thus, the candid character of a photo is unrelated to the subject's knowledge about or consent to the fact that photos are being taken, and unrelated to the subject's permission for further usage and distribution. The crucial factor is the actual absence of posing. However, if the subject is absolutely unaware of being photographed and does not even expect it, then such photography is secret photography, which is a special case of candid photography.
The person who is generally credited with being the first available light "candid" photographer is Dr. Erich Salomon who photographed the social elite in Berlin, Germany and politicians and diplomats during the late 1920s and early 1930s with a 1 3/4 x 2 1/4 glass plate or cut, sheet, film camera called the Ermanox, fitted with an f/1.8 Ernostar lens. The Ermanox was introduced by the Ernemann-Werke (Works) of Dresden, Germany, in 1924.
It was said by the French Minister of the Colonies Aristide Briand, that "There are just three things necessary for a League of Nations conference: a few Foreign Secretaries, a table and Salomon". On seeing Salomon's photographs, so utterly different in revelation from the traditional, posed, studio portraits or the formal, flash-powder illuminated, group photos, an English editor called them "candid photographs" a phrase which stuck with the public.
Ironically, the camera most suited to Salomon's approach, and which came to be dubbed as the "candid camera", was the Leica, the camera designed by Oscar Barnack and introduced by the Ernst Leitz company in 1924 and which was the forerunner of all 35mm cameras of today.
Some professional photographers develop candid photography into an art form. Henri Cartier-Bresson might be considered the master of the art of candid photography, capturing the "decisive moment" in everyday life over a span of several decades. Arthur Fellig, better known as Weegee, was one of the great photographers to document life in the streets of New York to often capture life — and death — at their rawest edges.
Almost all successful photographers in the field of candid photography master the art of making people relax and feel at ease around the camera, they master the art of blending in at parties, of finding acceptance despite an obvious intrusive element - the camera. How subjects react to photographer's presence with the camera depends on how knowledgeable the artist is on the craft, the approach and the execution of the shot. This is certainly true for most celebrity photographers, such as René Burri, or Raeburn Flerlage.