The Most Important Photographer You've Never Heard About

At least I'd never heard of Jerome Liebling, a mentor to documentary filmmaker Ken Burns and many others. Make sure you enlarge the photo they feature and check out the multimedia homage to his work. It's the sort of stuff that will keep newspaper websites competitive. One comment, in the multimedia tribute, Ken Burns says that Liebling is his mentor "in the BEST sense of the word." Is there a worst sense, or a negative sense I'm not aware of?