What lighting technique might suggest a character experiences duality in personality?

Side lighting is an effective technique for suggesting duality in personality because it creates shadows that can illustrate contrasting aspects of a character's nature. When light is cast from the side, one side of the character's face may be illuminated while the other remains in shadow. This interplay of light and dark visually represents the complexity of a character's emotions or conflicting traits, highlighting the notion of duality. This technique can evoke a sense of mystery, tension, or inner conflict, effectively enhancing the storytelling and allowing the audience to discern that the character has multiple layers or facets to their personality.

In contrast, bottom lighting can create a spooky or unsettling effect, flat front light tends to flatten the image and can make a character appear more one-dimensional, while aero lighting is not a standard term in lighting design and does not have a clear association with conveying duality. Thus, side lighting stands out as the most suitable choice for expressing the theme of duality in characterization.