I had the pleasure of hanging out with Ed Colver at a party in The Brewery in Los Angeles a few years ago. He is a cool old timer with tons of stories. At the time, he was driving a great hearse with a Dodge 400 in it and his business cards were blank bereavement cards for funeral homes.
I asked him about this iconic photo which has always been one of the great hardcore album covers and posters. He said he took this shot handheld at night outside of a show in LA, using only the light from a hot dog vendor cart. He never uses a light meter, has never used one and has such a refined eye that he can judge the light and get the exposure right every time. Even in the studio.