Lighting for museum exhibitions is an art which attempts to balance two factors: the visitor's visual experience and the preservation of the objects this describes the latter factor. The nature of light is discussed: energy, the electromagnetic spectrum, color temperature, and color rendering index. Psychological factors are linked to a lowering of light levels such as the eye's required transition period and the perceived cooling of light. Visual sensitivity is reduced when viewing dark colors especially in the case of aged viewers. Factors which determine photochemical deterioration are outlined. The nature of the material exposed, the composition and intensity of the light, and the time of exposure are four criteria that must be considered when evaluating light damage. Light norms arose historically from a desire to seek a balance between viewing the object and reducing damage; they remain a useful guideline today. The reciprocity law and total light dose (in lux-hours) are discussed. Ultraviolet filters and diffusers, and measuring instruments for visible light, infrared, and ultraviolet are presented, along with various control measures and strategies to minimize fading. Guidelines for lighting objects for photography and filming are mentioned.