A review of the effects of light level on visual acuity, threshold contrast and the ability to discriminate colour is given. From this review a minimum luminance necessary to avoid serious deterioration in visual ability is identified. For low reflectance materials, this luminance corresponds to the minimum illuminance recommended for museums and art galleries. Allowing people to move close to objects to be viewed ensures that such an illuminance will be adequate even for small, low contrast objects. However, it remains to be established if this illuminance is adequate for elderly people.