The central component of each of these simple optical instruments is a ring of bevelled glass. Originally part of a Fresnel lens, the glass was designed for use in a lighthouse to gather stray beams of light and send them out at a consistent angle, thereby enhancing the light produced. Here this ability to treat light as a malleable material is used to paint bands of pale colour on the wall. From the beginning of his career, Eliasson has been interested in producing artworks that function as experimental set-ups; these works are examples of this approach.