How to sharpen your gobo image using a donut
A donut, is a thin metal or cardboard panel, similar in shape and appearance to a color frame, but with a small diameter hole intended to reduce off-axis rays of light being projected from a fixture.This increases sharpness of the light by reducing the effect of imperfect lenses. Donuts are designed to fit into the color frame holder directly outside the fixture, immediately in front of lens assembly. Because they are typically thin, doughnuts can often be placed in the same slot as a gel frame. Doughnuts are typically used in fixtures in order to sharpen the beam when a template is in place.
Used to increase the clarity of patterns and custom gobos by reducing halation therefore sharpening the projected image. The donut sharpens the definition of projected gobo images by blocking the unwanted light.