Movie Magic and the Glass Shot Special Effect
The Ancestor of the Hollywood Matte Shot
Hollywood movie magic dates back as far as Hollywood itself. Before the concept of using a double exposure on film known as a matte shot Hollywood used a far simpler method known as a glass shot. Like its descendent the matte shot a glass shot was used to enhance a set without the expense and time of building a large set.
The glass shot was composed by painting structures such as a building or a partial painting of a building on glass to blend in with already existing structures. The physics is simple, all recorded images are two dimensional; and the illusion is created by creating a composite in the two dimensional world.
The camera is placed in front of the glass and the painted structure becomes super imposed against the existing natural background creating a composite shot. Often the job was a slow effort that involved at least two men. The artist painted while the camera man peered through the view finder to observe the artist and ensure the painting meshed seamlessly with the background. Careful planning went into creating the glass shot.
It was important to know exactly where the live action would be taking place. If any actor or actresses passed behind the painting, they would be obscured by the painted structure and ruin the shot.
The location of the live action was not the only caution the director and the effects artist kept in mind. Glass always poses the problem of reflection and sun glare on the glass. Sometimes a full canopy was constructed above the camera man to shade the glass from the sun. The camera man and the camera were often draped in black to avoid casting a reflection on the glass.
A record of time, date, and weather conditions were also kept as a reference to shooting the scene. It is important that the weather conditions match the conditions of the painting on the glass. A large deviation in lighting conditions and shadow lengths could lessen the believability of the image.
Today most low budget productions are shot on video recorders. Be sure the automatic focus feature is turned off and the focus is set on manual. Compromising the focus and splitting the difference is sometimes necessary. The camera will play a game of tug of war between the image painted on glass and the live action in the background. Sometimes the focus must be split between both elements of painted image and background images. This method avoids over focusing in one area and under focusing in the other area; and creating a blurred image either with the painted image or the background.
As the scene is being recorded it is important that the camera is mounted on a tripod and remains stationary. Any movements such as panning, tilting, or zooming the camera will cause a sliding effect. The difference between the focal length from the camera to the painting and the focal length from the camera to the live action causes the painting on glass to appear as though it is sliding during any movement of the camera.
Suspension of disbelief is allowed by letting the actors or actresses interact with painted structures increasing the paintings material sense. One example of this method would be strategically placing a scaffold behind a painted stone wall and letting the actors walk along the scaffold. The scaffold is completely eclipsed by the painting in between the camera and the painting. It appears the actors are walking on top of a castle wall.
Today’s audience is much more sophisticated than the audience of early Hollywood. A glass shot should not last any longer than a few seconds. Too much time on the matte shot give the audience time to analyze the scene and discover it is enhanced. Glass shots lasting only a few seconds are good for forming an impression in the mind.
Editing the scene buffers breaking the illusion presented by the painting. Cutting back and forth between close up live action and the glass shot extends the viewing time without disrupting trickery of the special effects artist.
Using movie magic of the glass shot can enhance any production and increase the value of the setting while saving the money and time of constructing a large set. There are many ways to creatively use painting on glass in a set for enhancement. For a few dollars a production can constitute the illusion of a big Hollywood production.