What does specific illumination refer to in theatrical lighting?

Specific illumination in theatrical lighting refers to a controlled shaft of light. This technique is crucial in focusing attention on particular actors or areas on stage, allowing for targeted visibility that enhances storytelling. By using instruments such as spotlights, a designer can create a clearly defined beam of light that highlights specific elements of a performance, drawing the audience’s eyes precisely where they are intended to focus. This approach not only helps to illuminate key actions or moments but also contributes to the mood and atmosphere of the scene, guiding the audience's emotional response.

The other aspects of lighting mentioned in the options involve broader concepts or different techniques. For instance, while shadows can indeed be a product of lighting design, they do not encapsulate the idea of specific illumination. Backlighting, while an important technique to create depth or add atmosphere, doesn’t restrict itself to a defined area of focus like specific illumination does. Similarly, colored lighting encompasses a range of effects and doesn't pertain to the focused, controlled nature of specific illumination. Thus, the characterization of specific illumination as a controlled shaft of light accurately captures its function and purpose in theatrical settings.