Three-point lighting is a fundamental technique in cinematography that uses key, fill, and back lights to create depth and dimension in a scene. By adjusting the position and intensity of these lights, cinematographers can control contrast, mood, and visual storytelling. Lighting ratios play a crucial role in shaping the look of a shot. By manipulating the difference between key and fill light intensity, filmmakers can create various atmospheres, from high-contrast dramatic scenes to soft, evenly lit comedic moments. Understanding these concepts is essential for crafting compelling visuals.