All it takes is a mere tap of the finger to delete an image from a digital camera, every mistake or blah shot instantly erased, your Instagram followers none the wiser. But this advance in technological agility—this instant curation—deprives us of the charm, fascination, and trial-and-error evidence of analogue photography’s contact sheet, where multiple shots from the same photo session are laid out like Tarot cards for inspection. “Proof: Photography in the Era of the Contact Sheet” invites viewers to see the photographer’s eye at work and play—legendary sharpshooters such as Diane Arbus, Richard Avedon, and the recently deceased Robert Frank—and to divine what separates a photographic bullseye from a near-miss. With artists of this caliber, even the outtakes and discards offer clues to their genius or blessed luck. And some contact sheets, such as Harry Benson’s of the Beatles enjoying a pillow fight, resemble movie clips—slapstick antics from a cheerier time. —J.W.