iPhones are no longer cameras in the traditional sense. Instead, they are devices at the vanguard of “computational photography,” a term that describes imagery formed from digital data and processing as much as from optical information. Each picture registered by the lens is altered to bring it closer to a pre-programmed ideal. Gregory Gentert, a friend who is a fine-art photographer in Brooklyn, told me, “I’ve tried to photograph on the iPhone when light gets bluish around the end of the day, but the iPhone will try to correct that sort of thing.”