Pepper's Ghost is a special effects technique for creating transparent ghostly images. It works by reflecting the image of a ghost off of a sheet of plexiglass. IThis effect has been a staple of theaters and haunted houses since John Pepper popularized it in the 1800s. In this project, I am going to show you how you can incorporate this technique into your Halloween setup.
Step 1: How the Illusion Works
The main background and any live characters are positioned in front of the audience. The ghost is located off to the side where it is not in the direct view. The ghost room can either be black or a mirror image of the main background. A sheet of plexiglass is positioned in front of the audience and set at a 45 degree angle to both the audience and the ghost. At this angle the background remains clearly visible but the glass also partially reflects an image of the ghost. To the audience, it appears as though there is a transparent ghost in the scene in front of them.
Step 2: Create a Ghost in Your Pictures and Video
The pepper's ghost technique is an easy way to insert a ghost into your pictures and videos without using any software. All you need is a small piece of clear plastic such as plexiglass.
Set up your camera in front of the desired background. Position your ghost to one side of the camera. The ghost can be a person in a costume, an image on a computer monitor, or just a picture. Hold up the plexiglass in front of the lens at a 45 degree angle to both the camera and the ghost. The camera will see a faint reflection of the ghost.
You may also get reflections of other objects around your ghost. To avoid this, you can either set up your ghost in front black backdrop or you can put the ghost in a dark room and use a flashlight or lamp to light up just the ghost.
Step 3: Create a Ghost in a Window
Creating a Pepper's ghost illusion for a live audience is a little more difficult. All the components need to be scaled up and more carefully controlled. You also have to hide the ghost from all possible viewing angles.
Creating a ghost in a window is a good way to restrict the field of view and give you a little more control. First you need a large sheet of plexiglass (preferably at least half the size of your window). Next you need to set up a table underneath the window. Then use books or cardboard to make a surface that is level to the window sill. Prop up your sheet of plexiglass in the corner of the window at a 45 degree angle. You may wish to also use a clamp of some kind to help secure it in place. Then position your ghost figure to the side of the window just out of view.
You need the room to be dark so that the edges of the plexiglass won't be visible. As a result, you will need to illuminate the ghost with a lamp or flashlight. Because the room is dark, you probably won't need a black backdrop for the ghost as long as you are careful to illuminate only the ghost.
The result is a transparent ghostly figure in the window that stares at people as they walk by your house.
Step 4: Create a Ghost in a Doorway
Creating a ghost in a doorway is basically the same as the previous examples. However, the opening is much larger. This means that you will need a much larger sheet of plexiglass. I recommend getting the largest sheet available at your hardware store. This is usually a 4ft by 8ft (48 inch by 96 inch) sheet.
Position the ghost next to the door. Then prop up the plexiglass in the door frame at a 45 degree angle to both the doorway and the ghost. Make the room dark and illuminate the ghost with a flashlight or lamp. This setup is the most impressive because you can display a full sized ghost. Unfortunately, it is also the most expensive. A 4x8 sheet of plexiglass can cost several hundred dollars.
Step 5: Other Applications of the Pepper's Ghost Illusion
The pepper's ghost effect is also commonly used by stage illusionists to make objects or people appear and disappear. In this trick the hidden room is often the mirror image of the background. By changing the lighting of the two rooms, you can change which one is more visible to the audience.
The pepper's ghost technique is also how "holographic" stage performances are made. A projector above the stage projects the image onto a reflective panel on the stage floor. A sheet of clear plastic angled over the stage partially reflects the image to the audience. This gives the appearance of a "hologram" on stage. Examples of this are the Tupac "Hologram", as well as several performances by the Gorillaz and Miku Hatsune