What type of flag is specifically used to cut light, often creating patterns on scenes?

The correct choice is a cookie. A cookie is a piece of material, usually made from wood, metal, or a similar substance, that is used to create patterns and shapes with light by blocking it in specific areas. This effectively "cuts" the light and allows for shadows and patterns to be produced on scenes, adding texture and depth to the lighting setup.

In film production, cookies are often utilized to simulate natural light effects, such as the dappled light one might find filtering through leaves in a forest. This helps to create a more dynamic visual aesthetic rather than relying solely on flat lighting.

On the other hand, a diffuser softens light and spreads it out, while a scrim reduces intensity without necessarily creating patterns. A reflector bounces light in a controlled direction, enhancing overall illumination but not shaping it into distinct designs. Therefore, using a cookie is specifically geared towards the purpose of creating patterned effects on scenes, making it the ideal choice for this question.