Pepper's ghost

Pepper's ghost is an illusion technique used in the theatre, cinema, amusement parks, museums, television, and concerts. The illusion is performed by reflecting an image of an object off-stage so that it appears to be in front of the audience. It is named after the English scientist John Henry Pepper (1821–1900) who began popularising the effect with a theatre demonstration in 1862. This launched an international vogue for ghost-themed plays which used this novel stage effect during the 1860s and subsequent decades. The illusion is widely used for entertainment and publicity purposes. These include the Girl-to-Gorilla trick found in old carnival sideshows and the appearance of "ghosts" at the Haunted Mansion and the "Blue Fairy" in Pinocchio's Daring Journey, both at Disneyland in California. Teleprompters are a modern implementation of Pepper's ghost. The technique was used to display a life-size illusion of Kate Moss at the 2006 runway show for the Alexander McQueen collection The Widows of Culloden. In the 2010s the technique has been used to make virtual artists appear onstage in apparent 'live' concerts, with examples including Elvis Presley, Tupac Shakur and Michael Jackson. It is often wrongly described as "holographic". Such setups can involve custom projection media server software and specialized stretched films. The installation may be a site-specific one-off, or a use of a commercial system such as the Cheoptics360 or Musion Eyeliner. Products have been designed using a clear plastic pyramid and a smartphone screen to generate the illusion of a 3D object. The core illusion involves a stage specially arranged into two rooms or areas, one into which audience members can see, and a second (sometimes referred to as the "blue room") that is hidden to the side. A plate of glass (or Plexiglas or plastic film) is placed somewhere in the main room at an angle that reflects the view of the blue room towards the audience. Generally, this is arranged with the blue room to one side of the stage, and the plate on the stage rotated around its vertical axis at 45 degrees.