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We shot the HDTV test pictures for the FCC ACATS (Advisory Committee on Advanced Television Service) in the Ed Sullivan Theater before Letterman moved in. We used all tube cameras, because HD CCDs were not yet in existence (early 90's). We had one BTS HD camera (using Saticons) that could have its modules switched to do 1050 interlaced (960 active lines) and 525 progressive. We had a Sony, which did 1125 iinterlaced, 1035 active (Japanese standard at the time). A second BTS camera was set up to do 787.5 progressive (720 active), the format proposed by Zenith and AT&T (and supported by MIT). Actually, this camera head could accept the the modules, but its viewfinder had been modified to 47 kHz sweep and could not be switched. Also, the video bandwidth on the BTS camera was a little short, rolling off at 25 Mhz or so. The internal control bus ran at 27 MHz, and when we wide-banded the progressive camera, we also had to make a bunch of ground and shielding changes to keep the 27 MHz clock out of the 720p video. All these formats morphed into the present 1080i and 720p.
The color rendition of the cameras was carefully measured on a Macbeth color checker chart and the matrix values adjusted to get signals as close as possible to the SMPTE standards. LeRoy DeMarsh of Kodak did the regression analysis. As I recall, the Sony was farthest off from what we wanted to start with, but we got a good match after changing values. There was also a problem with the "burn-in" of the Saticons - measurements made shortly after opening the iris differed significantly from measurements after the chart had been in place for several minutes.
Trying to get the least noise possible, we ran the BTS cameras at -3dB gain from nominal, putting us dangerously close to comet-tailing. Also, the 787.5p format had no viable image enhancer from the factory, and Zenith had a crash project (successful) to design and build one. This resulted in many long discussions and measurements to assure that the progressive and interlaced enhancement settings were not unfairly favoring one or the other.
The Sony camera used Sony Saticons, and the BTS cameras did too - but Sony kept their special low-noise FET preamps to themselves, and the BTS factory had to unsolder the preamps, which were soldered directly to the front of the tubes, and substitute the more noisy FETs that they could get.
I recall talk of the magnetic fields, but I think we had no problem - the cameras were kept away from the back wall.
One more thing - the theater had a beautiful but broken stained glass panel in the middle of the ceiling. Does someone know if it was restored, covered, or removed when the theater was remodeled for Letterman?
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