What role do deep shadows and stark lighting play in film noir?

In the context of film noir, deep shadows and stark, high-contrast lighting serve as the genre's most notable visual features, functioning to heighten the sombre tone of the narratives. These techniques, which trace their roots to German Expressionist cinema, were used to underscore the isolation of the typical noir hero from society.1

By utilizing low-keyed lighting, directors and cinematographers—such as John Alton, who collaborated with Anthony Mann—were able to convey thought and emotion through cinematic style. These visual elements helped embody the collective sense of uncertainty, disillusionment, and fear prevalent in the post-World War II era. The resulting dark, brooding atmosphere creates a world that feels corrupt and claustrophobic, effectively reflecting the disenchantment of the times.23