In film, nudity may be either graphic or suggestive, such as when a person appears to be naked but is covered by a sheet. Since the birth of film, depictions of any form of sexuality have been controversial, and in the case of most nude scenes, had to be justified as part of the story. Nudity in film should be distinguished from sex in film. A film on naturism or about people for whom nudity is common may contain non-sexual nudity, and some non-pornographic films contain brief nude scenes. Nudity in a sexual context is common in pornographic films or erotic films.