“[T]he Polaroid Collection has 16,000 prints by 120 recognized masters,” among them Ansel Adams, Phillipe Halsman, Mary Ellen Mark, Robert Mapplethorpe, Robert Rauschenberg, Inge Morath, and Margaret Bourke-White. Sotheby’s is to auction 1,300 prints from the collection next spring — though some artists and former employees say Polaroid never owned them.