A body double is a general term for someone who substitutes for the credited actor of a character in any recorded visual medium, whether videotape or film. The term is most commonly used in the context of head-to-toe (or nearly) shots involving nudity. For example, Catherine Bell served as a nude body double for Isabella Rossellini in the movie Death Becomes Her. More specific terms are often used in special cases; a stunt double is used for dangerous or sophisticated sequences. This is in contrast to a stand-in who replaces an actor for non-filming purposes such as scene arrangement and lighting adjustments.
Stunt double or body double can both be used for cases where special skills are needed—anything from playing the piano, to competitive skiing.
Also, if only a part of the body is shown, the term might be more specific; probably the most common is a hand double, who is used to shoot inserts where only the hand or arm is in the shot. These inserts are often shot by the second unit with a double at a later point in production primarily because it allows the main unit to use the lead actors' time more efficiently. Another common body double is the butt double, mostly used with TV, since whole-body nudity isn't as common in that medium. The term stunt butt is also attested.
A production scene photodouble portrays a double of the lead "star" actor for the director. A double will be seen on camera during the movie. Some of these many "double" acted scenes could be long or wide 'establishing' shots, complicated 'over-the-shoulder' main lead actor's dialogue sequences or in quick 'insert' close-up shots involving only showing actor's body parts.
The photodouble must say the dialogue lines in the same lead actor timing and also reproduce the exact physical actions "blocking" in co-ordination with the other principal "star" actors in that scene to make this scene 'real' since it will be seen in the final cut.
Usually the "double's" face is kept from being seen on camera. This way the "star" can work in fewer scenes and the "star" lead actor can be literally filming in two scenes at once. And in this way, a good cast photodouble can help speed up the day's production and is a necessary and valuable cast person for a film.
The 1984 film Body Double, directed by Brian De Palma, featured a plot that hinged on the discovery that one character had in fact served as a body double for another; whether the nude scenes in question were actually done by either of the two actresses or by an uncredited body double is unclear.
Political/military figures have sometimes used body doubles (whose resemblance may have been surgically enhanced) during public appearances, in order to mislead observers for various reasons.