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.

It's a little bit like talking about the life of writing. The life of writing may be about many things, but it always begins with the writer. With the kernel of an idea, or a character, or an idea or a theme, or even an outcome. But for documentary photographers, photographs begin at that intersection of the real world and the imaginative inner world.

I had luck, but I worked hard and I suffered. It's not just photography I'm talking about. It's about whatever dream you want it to be.

There isn't an aspect of book creation I don't enjoy, and there has always been a book in my life to dream about or work on.

I did a story for the Geographic on Meriwether Lewis and William Clark, and Stephen Ambrose was the writer. He said, "I've got the easiest job in the world. I just have to re-tell the story of the greatest fishing, camping, hunting, canoeing trip of all time. You, Sam, have the hardest job, which is, pretend like nothing has happened in the last 200 years.

Above all, it's hard learning to live with vivid mental images of scenes I cared for and failed to photograph. It is the edgy existence within me of these unmade images that is the only assurance that the best photographs are yet to be made.

There are a lot of ways to be expressive in life, but I wasn't good at some of them. Music, for instance. I was a distinct failure with the cello. Eventually, my parents sold the cello and bought a vacuum cleaner. The sound in our home improved.