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Brains Behind the Wall

Oct 1, 2008 12:00 PM, By Jay Ankeney

Designer David Niles explains the design and development of Comcast Center’s gigantic LED display.

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HD technology pioneer David Niles and his production team used a Panasonic AJ-HPX3000 camera to capture bluescreen footage for the wall. The footage was recorded to 10-bit uncompressed computer RAID storage and backed up to DVCPRO HD tape.

HD technology pioneer David Niles and his production team used a Panasonic AJ-HPX3000 camera to capture bluescreen footage for the wall. The footage was recorded to 10-bit uncompressed computer RAID storage and backed up to DVCPRO HD tape.

Part of the installation's constraint was that the videowall had to be hung while the Comcast Center's construction was still being finished. So, for three months, the contractors hired by Barco could only start work at 8 p.m. and had to have their lifting equipment and scaffolding cleared out by 6 a.m.

They also had to deal with the fact that, due to the lobby's changing level of ambient daylight, the wall only has to put out 200 nits of illumination at night, but needs to increase to 1,200 nits in the afternoon. A mechanism inside the wall accommodates this need by constantly adjusting the wall's brightness. To compensate for the heat generated by these power consumption variances required by the LEDs, eight air-conditioning fingers run down the back of the screen in an artificially created plenum. These maintain the wall's temperature within tolerances that prevent expansion and contraction gaps from appearing between panels.

By the beginning of May, the LED modules were turned on, and Niles began an extensive testing process to set their uniformity, brightness, and performance continuity. Niles's team had been putting the wall's content-creation system together in the Niles Creative Group studios back in New York. They transported it to the Comcast Center, where it was installed May 15, 17, and 18.


Niles wanted the content on the wall to be ever-changing to maintain a sense of surprise for the viewers during the few minutes they are walking through the lobby. He came up with the idea of using families of background images, which he refers to as “content buckets,” and decided to have a set of repeating life-sized human characters play on top of them. A cast of up to 22 performers, including 10 main personalities, was chosen to represent the “Philadelphia everyman doing extraordinary things” during production of the original content for the wall, as Niles explains it.

Sometimes these people are swinging from a trapeze over the wall. Others may be riding past on a giant pencil. Since images of these characters appear at random times over changing background scenarios, this adds to the videowall display's complexity. The cast has become quite popular to repeat visitors to the building, much like characters on a TV show or movie.

Niles determined that the wall's content would exist in four different worlds. Since the background of the display mimics the surrounding walls, it can be made to look invisible so the images in front of it appear, in his terms, “behind the screen.” A second world plays on the screen itself in what he calls “the flat world.” Then a third world can exist in a visual space that seems to be about 4ft. in front of the wall, and that is where most of the characters play. The fourth world won't be presented to the public until a special Christmas display takes over the wall during the upcoming holiday season.

The background scenarios, which can vary from a wilderness landscape to dazzling NASA images from space, are scheduled to coincide with the time of day as the pattern of skylight in the atrium advances with the hours. At 10 a.m., visitors may see stock-market quotes included in the parade of images, while in the afternoon, an airplane may fly over a forest panorama trailing a “Good Afternoon” banner. As you'd expect, the nature scenes track the changing seasons.

Having a 10-million-pixel display upon which to paint his images, Niles used three HD cameras to shoot the super-wide nature panoramas. He actually employed several of Sony's HDV models, sacrificing a bit of HD's ultimate recording resolution in favor of field-production economy and ease of mounting on a triple-camera rig. However, when they are stitched together, this gives his combined images three separate vanishing points — a distinctive perspective that has to be seen live to appreciated, especially when the cameras pan or tilt in unison.

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