An SLR camera is a type of camera whose name is derived from the flipping mirror located inside the body. This mirror reflects the light passing through the lens upwards into the optical viewfinder. As a result, the user sees a precise image of the scene in the viewfinder, exactly as the lens "sees" it. A special optical prism, known as a pentaprism, is used to ensure the correct display of the image in the viewfinder (uninverted and correctly oriented). The moment the shutter button is pressed, the mirror quickly flips up, clearing the path for the light, which then falls onto the image sensor and creates the photograph. This mechanism is responsible for the typical sound and the brief black-out of the viewfinder image during exposure. SLR cameras are characterized by the ability to use interchangeable lenses and by the use of an optical viewfinder, which, unlike an electronic one, shows the scene without any digital processing or delay.