Cinema has developed a very specific vocabulary for post-apocalyptic stories: Deserted streets, decrepit technologies, nature’s return to power, ruined landmarks. Although Richard Matheson’s novel “I Am Legend” was first published in 1954, this third adaptation of the story, after “The Last Man On Earth” and “The Omega Man,” makes excellent use of the imagery offered by films released after the novel. There’s a bit of “12 Monkeys” in Francis Lawrence’s vision of a world depopulated by a virus, and “28 Days Later,” and “The Quiet Earth,” and many others. But for all the tried and true vocabulary, Lawrence succeeds in overcoming the familiarity to deliver something unsettling and melancholy. When the last remaining human on earth, military virologist Dr. Robert Neville (Smith), scavenges lifeless homes for survival resources, we get a glimpse of interrupted lives —