What are the mechanical flaps on lighting instruments that control the shape of the light called?

The mechanical flaps on lighting instruments that control the shape of the light are known as barn doors. Barn doors are hinged panels that can be adjusted to open or close, allowing the user to alter the beam of light being emitted from the instrument. This provides precise control over how much light spills into specific areas, creating defined edges or softening the light for various effects.

In contrast, gels are used to change the color of the light, dimmers adjust the intensity of the light, and reflectors are used to redirect and enhance the light's output but do not shape the light in the same manner as barn doors. Understanding these distinctions is crucial for managing lighting design effectively in film and theater productions.