At the time of this paper (1962), there was no specifically defined guidelines for museum lighting. The eye adapts itself to the general conditions of viewing. For this reason, the eye is no judge as to the absolute level of illumination. Therefore, a light meter should always be used. Light can fade paint, as well as age paint, increasing its refractive index (leading to pentimenti). Light can also deteriorate varnishes. It is important to be concerned about light levels over 150 footcandles in the exhibition of art work.