Barn doors allow the emitted beam to be separately restrained in each of the four directions and provide improved glare control.
A cylindrical anti-dazzle attachment also restricts the view into the luminaire and reduces glare, but without the flexibility of barn doors.
The anti-dazzle attachments are usually externally mounted on the light head. Glare limitation increases with the size of the anti-dazzle attachments. The black painted finish absorbs light and reduces the luminance contrasts.