For a reader downloading a PDF on his directorial style, look for his quotes on the "silence" in cinema. Ratnam is a master of the pause—the moments where the camera movement replaces the dialogue. He often asserts that cinema is primarily a visual medium, and if the audience doesn't understand the story by looking at the frame, the dialogue has failed.
Painting with Light: Technical Mastery and Mise-en-Scène in the Works of Mani Ratnam conversation with mani ratnam pdf