How did expressive lighting create mood in D.W. Griffith’s films?

At a time when the prevailing convention in filmmaking dictated flat and uniform illumination for every element in a scene, D.W. Griffith pioneered the use of expressive lighting to create mood and atmosphere.1

While earlier directors had occasionally employed various lighting devices, Griffith was the first to practice them with the care of an artist, rationalizing their use within the overall structure of his films. By moving away from standard, uniform lighting, he was able to use light and shadow to complement and reinforce the dramatic situations within his narratives. This innovation allowed him to heighten the emotional intensity of his work, contributing to his role as a foundational figure in the development of classical narrative film.123