The neatest part of this book I'm working on - to me - are the pictures that show the process... Because photographers... think things through and... it isn't luck, and it isn't random and it isn't accidental. It isn't.

I did it once, and National Geographic recruited me. I did it primarily out of curiosity. A lot of legendary photographers had worked on that campaign. Ernst Haas had done the early photography, and I knew him. There's a lore in photography about that campaign, and I was curious.

That statement [ Stephen Ambrose:'You, Sam, have the hardest job, which is, pretend like nothing has happened in the last 200 years.'] woke me up to the fact that the landscape that Lewis and Clark came across was greater than the Serengeti. And it's gone.

My first priority when taking pictures is to achieve clarity. A good documentary photograph transmits the information of the situation with the utmost fidelity; achieving it means understanding the nuances of lighting and composition, and also remembering to keep the lenses clean and the cameras steady.

I have this awareness that the more dynamic the situation is, the more on guard I need to be that the dynamic isn't controlling the situation. I found that myself in the Galapagos. For the first time in my life I was around very exotic animals, colorful, beautiful, and immediately present, all around. Birds, turtles, iguanas, seals. I was being seduced by their exoticism, I was taking pictures.The pictures weren't well lit, there was no moment in play, there was no depth to the pictures. I was just gawking with my camera at something I'd never seen before.

One of the things that I most believe in is the compose and wait philosophy of photography. It’s a very satisfying, almost spiritual way to photograph. Life isn't’ knocking you around, life isn't controlling you. You have picked your place, you’ve picked your scene, you’ve picked your light, you’ve done all the decision making and you are waiting for the moment to come to you.

My father taught me photography. It was his hobby, and we had a small darkroom in the fruit cellar of our basement. It was the kind of makeshift darkroom that was only dark at night.