That looks like a still from some of Bruce Browns footage titled Hare & Hound Classic shot in 67 as a preliminary work for On Any Sunday. I believe (according to him) he was the first guy to shoot a desert race form a Helicopter. Buy this dvd and watch amazing footage of over 1,000 riders land rush start. Features incredible footage of a very young J.N. Roberts dominating race.The picture was labeled "Mojave Desert 1971" That's all I know about it.