A teleprompter is the modern incarnation of “smoke and mirrors.”
There was this method called “Pepper’s Ghost” in the 1860’s that used a stretched piece of thin fabric placed between the audience and the stage. It was unnoticeable unless light was reflected off it. The actors on the stage would do their thing until the phantom was needed to appear. Until that time, the actor playing the phantom would be in a darkened orchestra pit, below the main stage.
When light was projected on the phantom actor, their image would be reflected in the fabric above, causing it to be “on stage” with the actors. The two worlds would interact, and at some point, the phantom would be “extinguished” and the day was saved. The same idea is still used in modern stage presentations with Musion and also Disneyland’s Haunted Mansion.
So, how does a teleprompter work?
I profiled the presidential teleprompter in an earlier post. A traditional camera mounted teleprompter allows the speaker to look at the camera like normal. However in this case, their script is superimposed over the lens. This way it appears to the audience that the actor is making direct eye contact with them while still speaking from the heart. Teleprompter software takes a normal script file (in a format like .doc, .odt, or .rtf) and converts it into large letters on a contrasting background, typically, white letters on black.
This signal is sent from a laptop, tablet, or even phones, through a cable to the teleprompter monitor. Transmission can be via Bluetooth as well, but for mission critical shoots, I suggest staying with hardwired systems. These monitors normally range from 7″ to 20″ although there are some great exceptions when the distance is exaggerated. The monitors need to reverse the image because when it is reflected through the mirror, it appears as the correct orientation to the speaker. This can be accomplished via either the teleprompter software, or by special monitors that scan reverse the image. Alternatively, Hall Research makes a great box called a SC-VGA-2B that takes VGA signals and flips them.
These words then appear to float in space so that the speaker can look into the camera and read them. A teleprompter operator feathers the speed of the script to match the pace of the speaker. If the speaker slows or stops, then the operator will follow. Some modern, lower grade systems can operate without an operator by using a preset speed on loop, but it can be unnerving to the speaker to follow a machine. For example, the number “$23,577” takes up a small amount of space on the screen, and would go by quickly on a preset speed, but to speak out loud “twenty-three thousand five hundred and seventy seven dollars” takes a lot longer. Any sync would be destroyed and your speaker would be frustrated.
The prompter operator also interacts with the camera crew and sets up the teleprompter equipment so everything is connected to the tripod and balanced correctly. Plus, an operator edits the script and often wordsmiths the lines. Phrases that look good on paper don’t always sound great when spoken aloud.
Typically, the speaker will rehearse several times on paper, then advance to the teleprompter, make any edits, and only then will they hit the record button.
For more of a teleprompter definition and some other great images, here’s the Wikipedia article.