The show in California, “More American Photographs,” is being organized by the Wattis Institute for Contemporary Arts. The idea was to commission a number of photographers to produce new work about America in the spirit of the Farm Security Administration photography of the ’30s and ’40s. I decided to use the most famous F.S.A. picture as my reference point: Dorothea Lange’s “Migrant Mother (1936).” I’m fascinated by the whole notion of iconic pictures. Of the 80,000 F.S.A. pictures, why is this one so memorable? This is a particularly interesting question for a photographer working in the age of Flickr. So just as a painter might go to a museum and sketch from one of the masters, I attempted to make my own migrant mother picture. It was a fascinating exercise.