Harry Callahan was “the greatest visual artist who ever grew to maturity in Chicago,” writes Alan Artner. He was “up there with Alfred Stieglitz, Paul Strand, Edward Weston and Ansel Adams. His work has been collected by every major art museum and has been seen in several retrospectives. But while most Chicagoans have heard of Adams, ask about Callahan and you’re likely to hear only about the movie cop played by Clint Eastwood, suggesting that special measures need to be taken.”