An iris shot is a technique frequently used in silent film in which a black circle closes to end a scene.
The iris shot is divided into two types depending on their use. An Iris out is used at the end of a scene, and an Iris in is used at the start of a scene, often after a previous iris out.
Some non-silent era slapstick comedy, such as that of Red Skelton, Benny Hill, and Warner Bros.' Road Runner cartoons, employ the iris shot as an homage to the silent film era. Iris shots are used to put emphasis on a particular aspect of film, usually something of importance.
In some cartoons and live-action films, iris shots are used as a way to break the fourth wall, usually for comedic purposes or to allow characters to interact with the audience. Examples of this include characters trying to escape through the closing iris, addressing the audience with a one liner before the iris closes, or holding the iris open to try and continue a monologue.