The varieties of daylight and the emotional effect on humans are mentioned. Light has three quality aspects: the quantity of light, the spectral distribution, which gives an impression of warm or cool colored light, and the character of light, which gives the impression of direction, depending on how diffuse or direct the light is. For lighting designs, it is essential that one can reproduce the desired light effects, so proper measuring methods are needed for color temperature, color rendering index, contrast, and light beams. An objective measure to express light color is the color temperature of a light source. The well known light sources (the sun, fire, candle, and glow lamp) each have their own temperature which is related to the color of the light radiated. These light sources are therefore called temperature radiators. One can express the light color in the absolute temperature of that moment, the color temperature in Kelvin (K). The color temperature says everything about the light color of a source, but not about the color rendering qualities of the same source. The color rendering index (R_a) is the objective measure to compare lamps with each other on this point. Displaying works of art, and at the same time dealing with conservation problems always results in a compromise. One can restrict annual exposure, stated in terms of the product of illuminance and hours of exposure. There is a direct relation between exposure and damage. Different light sources, however, can give different fading damage. The damage factor of different light sources is explained. Finally, the light accent on a display is discussed. The firm Philips has developed a scientific method of analyzing the beams, the results being laid down in the so-called K-beam classification. This technique allows the size of the principal parts of the beam to be identified and the true extent of its visual impact on the display to be predicted. The classification defines five types of beams, from K₁, a profile spot without any spill light, to K₅, a uniformly wide beam without any visible spotting.