The project for the transformation of the old Orsay railway station into a museum to house collections of 19th century French art, chose not to interfere with the 1899 architecture by Laloux, but instead, to characterize it with new lighting, materials and colors. The lighting required special attention: not wishing to add extra elements to the pre-existing structures, the re-development of the spaces and the architectural transformation of the station into a museum had to provide new lighting solutions in themselves. The structure of the station includes large glass surfaces, which created a serious problem of interference between the presence of natural light and the large variation in the size of the spaces. The choice to use discharge lamps was dictated for two strongly conditioning motives: the relatively low level of useable power allowed - due to the existence of serious air conditioning problems - and the presence of daylight almost everywhere. The museum thus required the use of sources with a color temperature relatively close to that of discharge lamps.