“To take a photograph is to participate in another person’s mortality, vulnerability, mutability,” Susan Sontag wrote in On Photography. “Precisely by slicing out this moment and freezing it, all photographs testify to time’s relentless melt.” It’s been roughly 200 years since the French inventor Nicéphore Niépce captured the view of his courtyard using a camera obscura and a pewter plate—the first photograph! Since then, the medium that began as documentation has expanded into an art form. Take Man Ray, whose rayographs imbued his photos with a surreal, dreamlike haze. Or Dorothea Lange, whose unflinching portraits from the Great Depression opened a portal into everyday American life, evoking emotion that the written word never could. To celebrate the bicentennial of photography—1827 to 2027—a new exhibition traces the medium’s entire history through approximately 700 works. —Maggie Turner