[martin417]

The filter we used was actually a lens from a pair of laser safety goggles. We use IR lasers at work, and have safety goggles to prevent eye injury. What we found is that the incandescent lighting that First uses at events is very heavily weighted towards the IR end of the spectrum, so filtering out a bunch of the IR helped leave bandwidth for the colors we wanted to detect.

In addition, we used a fisheye lens to give us a wider field of view.