Research Brief

Pepper's Ghost is an optical illusion technique named after English scientist John Henry Pepper, who popularized it during an 1862 Christmas Eve theatrical production of Charles Dickens' The Haunted Man and the Ghost's Bargain at the Regent Street theatre in London. The technique was actually invented by English engineer Henry Dircks in 1858, though it became known as Pepper's Ghost after Pepper implemented a working version in 1862. The illusory stage effect dates back to the 1500s when playwright Giambattista Della Porta described an apparatus allowing theater audiences to 'see in a Chamber things that are not,' and was later popularized for theatrical use by John Henry Pepper in the 1860s.

The original Pepper's Ghost optical illusion involves placing a large piece of glass at an angle between a brightly lit 'stage' room into which viewers look straight ahead and a hidden room that is kept dark and holds a 'ghostly' scene. When the lights in the hidden room are slightly raised to illuminate the scene and the lights in the stage room are slightly dimmed, the apparition appears to the audience. When light from a bright object reaches the transparent material, a portion of the light will reflect—for typical plastic, glass, or acrylic, this will be about a 4% reflection. To recreate this at home with a phone and window as described in the video: Set up your camera in front of the desired background, position your ghost to one side of the camera (which can be a person in a costume, an image on a computer monitor, or just a picture), hold up plexiglass in front of the lens at a 45 degree angle to both the camera and the ghost, and the camera will see a faint reflection of the ghost. To avoid unwanted reflections, you can either set up your ghost in front of a black backdrop or put the ghost in a dark room and use a flashlight or lamp to light up just the ghost.

In Disney's Haunted Mansion, guests travel along an elevated mezzanine, looking through a 30-foot (9.1 m)-tall pane of glass into an empty ballroom, while animatronic ghosts move in hidden black rooms beneath and above the mezzanine. The objects you see in the ballroom are really there, like the table, the organ, and the chandelier, but the animatronics are not actually in the ballroom—instead, there are animatronics in the spaces above and below your buggy where you can't see them, and hidden lights shine directly onto the animatronics so that they reflect on the glass wall. The Haunted Mansion at Disneyland officially opened on August 9, 1969. Beginning in 1958, Imagineers Rolly Crump and 'Illusioneer' Yale Gracey were given the task of creating the numerous special effects for the Haunted Mansion, and many of the effects they developed were inspired by some of the illusions created by 19th century magicians including the famous 'Peppers Ghost' effect.

For DIY implementations, multiple approaches exist: You can use a letter-sized transparency film sheet (like the ones used for overhead projectors) and a globe display case that fits over your smartphone or tablet—fold the circular film sheet and insert it into the globe, trim as needed until the sheet rests in the globe at a 45-degree angle, then find a video of an object against a black background and place the globe on top of it. Anything black in a Pepper's Ghost illusion becomes transparent, so the focus of the video will appear to float. The effect is highly scalable and requires minimal investment—transparency sheets, clear plastic containers, or even smartphone screens can serve as the reflective surface. Modern variations use high-performance projectors, scrim fabric instead of glass, and animation software, but the core principle remains unchanged from the 1860s.