From his home in Long Beach, California, Mark Ruwedel, shows us around his studio and talks about why it can take him years to complete a photographic series, after an evolving process of sifting and selection.
One such series involved a 14-year study of old abandoned railroads in the American and Canadian West. He describes documenting these incredible feats of engineering, and a history of human endeavour long lost and almost forgotten.
This film is one of Tates Global Studios series, in which we visit artists studios around the world. The artists also take part in question and answer sessions with visitors at Tate Modern, via online video.
You can find out more about Global Studios here.