The other day, in the parking lot of a large auto supply store, I spotted a man standing in front of his sporty mid-range vehicle gazing in rapture at the violet-colored light of his headlamps. He looked overjoyed – presumably with the recent purchase and installation of his new lamps.
I would not have been looking quite so thrilled in his situation, because if you’re standing up straight just three or four meters from the hood of your car, you shouldn’t be able to see much of the light at all. After all, that light should be on the road and not in the region above the headlamps. Everything shining upwards is really lost light. Engineers call it “stray light” and try to eliminate it as much as possible.