Final answer:
The cool light from the other side of the stage is known as fill light, used to reduce contrast and soften shadows created by the key light in a three-point lighting setup.
Step-by-step explanation:
The cool light from the other side of the stage you’re asking about is typically known as fill light. In stage lighting, the fill light is used to reduce the contrast and shadows created by the key light, which is the primary light source. Fill light is softer and doesn't cast distinct shadows, making it an essential component in three-point lighting setup used widely in theatre, photography, and film. For example, if we consider a scene with a single table lamp, a lighting designer might use additional key and fill lights to enhance the illumination while still maintaining the illusion that the light comes exclusively from the lamp. The use of fill light allows for a more evenly lit scene and helps the audience focus on the performers without distractions from harsh shadows.