To know ahead of time what you're looking for means you're then only photographing your own preconceptions, which is very limiting, and often false.

The people who are garrulous and wear their heart on their sleeve and tell you everything, that's one kind of person, but the fellow who's hiding behind a tree and hoping you don't see him is the fellow that you'd better find out why.

The words that come direct from the people are the greatest... If you substitute one out of your own vocabulary, it disappears before your eyes.

Dorothea Lange Quotes