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Prompter UniversityPO Box 11929
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Mechanics of a Teleprompter The teleprompter is extremely simple in concept. Bounce text off of a mirrored surface into the eyes of the presenter. How that happens involves a lot of disciplines. There are three elements to a teleprompter: Text Source, Reflector and Control function. The text source in modern teleprompters is an LCD flat panel computer display. But early-on the teleprompter took on a different look driven by technology limitations. Rolls of paper on which text was hand lettered was mechanically scrolled on top of a reflector in front of a television camera lens. An operator standing next to the camera controlled the scroll speed of the roller motor(s). The rolls, because of their mechanism noise and unreliability (constantly getting caught in the machinery and tearing), were moved to a remote table over which was mounted a b&w camera. The camera would pick up an image of the text and feed it to an a/v monitor pointed toward the reflector. The anchor would read the text off the monitor's reflection in the usual manner. The remote paper roll mechanism could be controlled and cleared with a minimal of effort, unlike the on-camera mounted roll teleprompter. The teleprompter reflector has seen its fair share of changes over the years. What started out as a beamsplitter, fragile (seems like it will shatter if you look at it the wrong way!), and fraught with video problems like light loss due to its thickness, and color shift due to its refracting design, has evolved to specially optically clear thin art glass, with antireflective rear optical coating. Not all teleprompters use the same reflector design. There are low end models that use flexible acrylic (plastic) reflectors, which scratch very easily. And there are those designs that still employ a beamsplitter, which are extremely expensive and difficult to replace, but are vital if you are shooting film. The reflectors are variously captured in a rigid metal or plastic housing (hood), or simply a metal frame with cloth hood. Metal is more robust, while plastic will crack from the heat cycles of a studio lighting system. Cloth hoods decomposed with light and heat over time, and will find the most inopportune time to collapse into the lens's field of view, ruining a shot. Reflectors for large format monitors are cut to a trapezoid pattern, others on smaller format monitor systems use a rectangular reflector. The difference has to do with the 'throw' (focal length) of the camera lens being used with the system. Trapezoid shape reflectors allow long length lenses to widen out significantly without vignetting (having the reflector housing cut off the image). Typical video production used on medium sets with one or two talking heads in lock-down mode (99% of teleprompter use) operated quite effectively with the rectangle reflector. Replacement cost and availability makes it an ideal reflector. With the advent of personal computers, teleprompting took a promising turn. The television industry immediately grasped the ideal of using a computer based titler (one of their first uses of graphics computers) to drive the teleprompter monitor, instead of the b&w camera/paper text roll combination. Smooth scrolling of text is something that a titler does well, but few have the capability of importing large text files - a requirement for teleprompting. But clearly the techs were marching in the right direction toward a totally quiet and mechanics-free teleprompter. Enterprising programmers developed the required fast smooth scrolling, large format, easily captured and edited text file program that would run on personal computers. But the early computer hardware was so painfully slow that it took some time and a certain level of genius to accomplish a practical model. Today's fast machines should have made it easier to build smooth scrolling large format applications, but the opposite is true. Newer operating systems have risen to the occasion of higher speed processors by choking them with features designed to be used by the few, but forced to be purchased by the many. The result is that it takes the same genius to build code (a teleprompter program) that will both smooth scroll, and scroll fast enough to be practicable.
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