Source of Ansel Adams quote?

I just downloaded, "The Print,"  free:

Chris,

You have been kind enough to try to help me, which I do appreciate. Perhaps I should explain.

Suppose someone said I was lying when I claimed that Ansel Adams had said, “Dodging and burning are steps to take care of mistakes God made in establishing tonal relationships.” . I would look like an idiot if all the proof I could offer was that I had read it on the Internet. I need to know when and where he said it, and to whom. I also need to know whether that person was trustworthy and why a court of law should believe him. Ideally, I would find these words in a published book written by Ansel Adams.

I have already researched one famous quote, from Monet, and found that many people have got it wrong. The original source was not where some people said it was. The closest to an original source was the writing of someone who claimed that someone he knew had heard it from Monet's lips. It may be true, but the words can hardly be firmly attributed to Monet. I would look a fool if I used them, just because they cropped up all over the Internet in various lists of quotations.

Here, for example, are two websites which do not give references; so, from the point of view of serious research, they are completely useless: