For those who only know Walker Evans from his crisp 1930s black and white photographs of towns, buildings factories, and sharecroppers are in for a surprise. Turns out that Evans collected postcards long before he ever snapped even one photo (“Walker Evans and the Picture Postcard” at the Metropolitan Museum of Art). He eventually collected 9,000 cards, depicting just about every topic imaginable: hotels, various jobs, street scenes, train stations, and capitol buildings. He studied all to hone his own eventual craft: photography. He even copied, not unlike amateur painters who imitate the greats. The exhibit shows 700 cards, just a fraction of his collection, along with a smidge of his own work. This exhibition was organized by photography department curator Jeff L. Rosenheim. It was derived from a huge supply that the Evans’s estate gave to the Met in 1994.