Pepper's Ghost - A historical overview
The original Pepper's ghost technique is a simple illusion which has been and is used in theatre, haunted houses, dark rides, and magic tricks. It is named after John Henry Pepper, a scientist who popularized the effect in a famed demonstration in 1862.
It actually has a very long history, dating back into the 16th century when it was first observed as an unusual effect by Giambattista della Porta who was a Neapolitan scientist and scholar. He is credited with a number of scientific innovations, including the camera obscura. His 1584 work Magia Naturalis (Natural Magic) includes a description of an illusion, titled "How we may see in a Chamber things that are not" which is the first known description of the Pepper's Ghost effect
The Victorian illusion was originally developed in 1862, by inventor Henry Dircks who developed the Dircksian Phantasmagoria, his version of the long-established phantasmagoria performances. The technique was used to make a ghost appear on-stage. He tried unsuccessfully to sell his idea to theatres. It required that theaters be completely rebuilt to support the effect, which they found too costly to consider. Later in the year, Dircks set up a booth at the Royal Polytechnic, where it was seen by John Pepper
Pepper realized that the method could be modified to make it easy to incorporate into existing theatres. Pepper first showed the effect during a scene of Charles Dickens's, The Haunted Man, to great success. Pepper's implementation of the effect tied his name to it permanently. Though he tried many times to give credit to Dircks, the title "Pepper's Ghost" has endured
The relationship between Dircks and Pepper was summarised in an 1863 article from Spectator:
"This admirable ghost is the offspring of two fathers, of a learned member of the Society of Civil Engineers, Henry Dircks, Esq., and of Professor Pepper, of the Polytechnic. To Mr. Dircks belongs the honour of having invented him, or as the disciples of Hegel would express it, evolved him from out of the depths of his own consciousness; and Professor Pepper has the merit of having improved him considerably, fitting him for the intercourse of mundane society, and even educating him for the stage"
Below you can see how the Pepper's Ghost technique was originally used for theatrical productions in Victorian times.
For the modern version of Pepper's Ghost, which is often called 3D holographic projection, please click here
The Pepper's Ghost effect works by reflecting the original (brightly lit) content (an actor dressed as a ghost - see above) through an upbacked mirror. It's like looking out of a window at nightime. You see yourself as a reflection from the window and the view out of the window. The reflection can look 3D and very real if the illusion is produced well. In Victorian days, the audience would often pay to just see the ghost (holographic type effect) on stage! There is no doubt that the Pepper's Ghost effect can be a visually powerful effect when produced correctly
By producing digital content and using a video projector or LED panels (or a display monitor for smaller systems), it is possible to "3D project" real video footage of products, life sized or bigger than life sized people, creatures and any sort of content when using computer graphic imagery (CGI)
The projection looks very much like a "holographic type effect" which is why it is often call 3D holographic projection but it should be noted that the Pepper's ghost technique is not a real hologram in the true sense of the word but the effect certainly does look "holographic".
The word hologram has now become a generic term for pretty much anything 3D, but a real hologram has parallax (http://en.wikipedia.org/wiki/Parallax). Parallax allows the viewer to actually look around the 3D image. With a real hologram you can look around the 3D image, but with Pepper's Ghost you do not get this effect. However, by clever use of the content, it is possible to make the content look very 3D and appear to be a hologram type projection. With Pepper's Ghost, eventhough it looks 3D, there is actually no real 3D and no parallax. The original content comes from a 2D source such as a video projector. It is therefore up to the content creation team to maximise the illusion of 3D by using certain tricks and effects which help the viewer perceive 3D from a 2D source. Some examples of 2D content that looks 3D can be seen below. Note the use of black all around the content. This is required for the Pepper's Ghost effect to work. The 3D content must be isolated against black. Black becomes a nothing (invisible) colour when viewed on a Pepper's Ghost system
With modern Pepper's Ghost productions, it is possible to mix the real with the virtual, i.e. real presentors and real objects with the holographic type effects. This works well for musuem projects and stage based events. Please see the video below which features a "live" presenter talking to the audience and video "holographic type" content running at the same time
Given that the original Pepper's Ghost was a Victorian theatrical illusion, the original patent for the effect has long since lapsed. This means anybody can make a Pepper's Ghost using an unbacked glass or plastic mirror. For small scale Pepper's Ghost illusions, glass or plastic is fine and easy to work with. However, large sheets of glass for large scale Pepper's Ghost projects are hard to handle so modern versions of Pepper's Ghost use a special foil mirror for the effect. The foil can be rolled up for transport and ease of installation. For the foil mirror to work, it must be held flat and at approx. 45 degrees
For further examples of various Pepper's Ghost projects, please click here
To see our FXimagePod, a smaller Pepper's Ghost, 3D holographic projection system, please click here