Light diffuser

A luminaire comprising:

• a light emitting arrangement configured to emit light;
• a housing, configured to house the light emitting element, and comprising a light exit window for permitting the exit of light emitted by the light emitting arrangement out of the housing;
• and
• a light diffuser configured to cover the light exit window to diffuse light exiting through the light exit window and comprising a film of light diffusive material, wherein:
• the film is corrugated to form a series of alternating ridges and grooves along a first direction (x) lying in a first plane, each ridge being located above the first plane and each groove being located below the first plane, such that application of a force (f1) to the film in a second direction (y) causes the film to curve or bend in the first plane;
• and
• the second direction lies in the first plane and is perpendicular to the first direction,
• wherein the housing has two opposing side walls, each side wall having a respective elongated slot in a respective inner wall and adjacent the light exit window for holding the light diffuser, and wherein the light exit window is curved and the light diffuser is configured to follow the curve of the light exit window.