The first and most obvious requirement was to achieve reproductions as faithful as possible to the “spirit” of the original photographs. The 1,642 original prints were scanned at the National Gallery. With Sarah Greenough and Mary Yakush, Robert Hennessey devised a printing strategy using black plus five colors, plus a selective tint, that could be variously combined to approximate the range of colors in Stieglitz’s platinum, palladium and gelatin silver prints. The second requirement was to reproduce the prints in a proportionate size, accurately reproducing minute differences between prints of a similar size.