Final answer:
To emphasize a single character on a crowded stage, the best two effects a director can use are lighting and costume. These elements work together to focus attention, set the mood, express character traits, and support the narrative of the production.
Step-by-step explanation:
To emphasize a single character on a crowded stage, a director can utilize a combination of lighting and costume. A well-designed lighting scheme can not only bring focus to a character but can also alter the perceived setting or mood, such as creating the illusion of a jail cell with strategically placed shadows or changing the color and texture of a costume to show character development. Costume design works hand-in-hand with lighting, as it also aids in character distinction but does more in terms of helping the audience understand a character's role and evolution within the story.
Moreover, lighting can impact the auditory experience, where a dimly lit scene can heighten the audience's attentiveness to dialogue, whereas bright lighting generally points to levity or humor. As part of the production design, costumes must align with the scenery and lighting to ensure a cohesive and supportive narrative. While props are important for detail and scenery sets the place, lighting and costume together provide a profound impact on character highlight and storytelling.