To intentionally shift the emotional tone of a scene from realistic to melancholic or eerie using artificial light, what accessory should an expert apply to the light source?

To intentionally shift the emotional tone of a scene from realistic to melancholic or eerie using artificial light, an expert should apply a color filter to the light source. A color filter, commonly known as a gel (short for gelatin, its original material), is a transparent sheet placed in front of a light. Its function is to selectively absorb certain wavelengths of light while allowing others to pass through, thereby changing the color of the light illuminating the scene. For a melancholic tone, the expert would choose gels that introduce cooler, often desaturated colors such as steel blues, muted cyans, or subtle lavenders, as these hues are psychologically associated with introspection, sadness, or a subdued mood. For example, a deep blue gel can evoke a sense of quiet sorrow. For an eerie tone, the expert would apply gels that produce unnatural or unsettling colors, such as sickly greens, deep magentas, or stark, desaturated blues and purples. These colors disrupt the viewer's expectation of natural light, creating a sense of unease, mystery, or foreboding. For instance, a lime green gel can make a scene feel distinctly unnatural and creepy. The color filter directly manipulates the light's spectral composition, which is the specific mix of different colors present in the light, allowing for precise control over the scene's emotional resonance.