Slightly off topic, but I sat through a presentation from Musco Lighting a few years back. Musco does a lot of baseball fields, not sure about football. The way they break it down is amazing; the entire field is broken down into 1 square inch segments and a program scans the grid to make sure every segment receives an adequate amount of candle power light. And of course there is a digital check system built to monitor the light output for continuous coverage.