The author first explains how to evaluate and take precise measurements of color variations affecting an exhibit piece, the real intensity of the light source, the light sensitivity of the object, etc. He then discusses findings on the optimum length of light exposure for a number of materials, including watercolors, oil paintings, paper, newsprint, textiles, whether exposed to daylight, incandescent lamp, halogen lamp, or fluorescent tube, with or without filter. General recommendations concerning exhibit lighting conclude the article.