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  • TV Broadcasting Gets Real-Time Lighting

Photonics Spectra
Nov 1996
Ruth A. Mendonsa

Sports fans are going to be a lot happier watching those all-important football games this season. One TV network is making sure its viewers don't miss out on the action when the players move from the sunlight into a shadowed area of the field or are obscured by smog or haze.

To overcome lighting problems encountered when televising outdoor events, Fox Sports Inc. has purchased from QVIS Corp. a dozen QVIS Light Equalizer units, a new technology that improves lighting in real-time by reducing or eliminating loss of visibility caused by shadows, glare or poor contrast. The technology allows an image shot outdoors to appear to have been shot under controlled lighting. Football play in shadows with traditional TV lighting, above, and with the QVIS Light Equalizer, right. The system was originally developed by Whittier, Calif.-based QVIS for use in medical, surveillance or military applications. Realizing that this technology had great potential for meeting the needs of the entertainment industry, the company began redesigning the system with an eye toward coverage of live events and reality-based programming.

The Light Equalizer box, roughly the size of a videotape recorder, receives a video signal between the source -- whether tape or live camera -- and the broadcast transmitter and digitally processes it in real-time. No changes to existing video equipment are required. Users can control the frequency spectrum and local contrast of any video image in real-time. The system employs digital filtering to perform a sophisticated convolution algorithm by analyzing a large neighborhood surrounding each pixel. It's like having separate automatic gain controls at every point in the image, each acting independently and automatically.

Analogous to a graphic equalizer commonly used in sound systems, the Light Equalizer has three basic controls. The first, high-frequency gain, is analogous to treble; it amplifies or attenuates high frequencies and is available with either a fixed transfer function or a more sophisticated locally adaptive transfer function. The second control, low-frequency suppression, is analogous to bass; it amplifies or attenuates low frequencies. The third control, kernel size, determines at what frequency the system differentiates between low and high frequencies.

According to Jerry Gepner, senior vice president of Fox Sports, the unit is installed between the camera control unit and the switching systems. "It uses adaptive circuitry -- the more you need it, the more it works. It can make a significant difference," he said. "When you need it, you need it badly."

Now it won't be necessary to lean in closer and squint to catch the details of that crucial play. It looks like the picture will be crystal clear.

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