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 subsequent usage such as distribution. The crucial factor is the actual absence of posing. 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.