On a recent spring morning, some 90 minutes before the Metropolitan Museum of Art opened, Dave Krugman, a 26-year-old photo retoucher from Bushwick, Brooklyn, ushered six friends into its cavernous halls through a side door near East 81st Street.
Unimpeded by crowds, they roamed the world-famous exhibitions. Mr. Krugman photographed his fellow adventurers posing above the main staircase, standing stone-faced in front of an ornately carved Roman sarcophagus and strolling past the pool around the Temple of Dendur.
The rapid rise of social media has created many unusual alliances, but few are more curious than those the bushy-bearded Mr. Krugman has formed with some of the leading cultural institutions in New York. He has earned his V.I.P. access because he is helping them — free of charge — build their profiles on Instagram, an app for sharing photos and videos.