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.

This might seem off the track, but an interesting thing to me that others could talk about better than I, but one of the growth areas in photographic education has been the so-called slow photography.

Though Geographic didn't publish that photo in the story that it was done for, "The Life of Charlie Russell," a cowboy artist in Montana. But later, maybe a year and a half ago, they named it one of the 50 greatest pictures ever made at National Geographic.

The class that I teach is called "The Life of a Photograph." It takes up the question, of the billion photographs that were taken today, how many will have a life, and why? So the new reality has made the question more pertinent, not less pertinent.

Teaching has never been far from my life. It's the most natural thing I do. Apparently, as I said, I cannot not do it.

For spiritual companions I have had the many artists who have relied on nature to help shape their imagination. And their most elaborate equipment was a deep reverence for the world through which they passed. Photographers share something with these artists. We seek only to see and to describe with our own voices, and, though we are seldom heard as soloists, we cannot photograph the world in any other way.

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.