Figure 2.

Light profiles, in photopic illuminance (solid gray, left ordinate scale) and in circadian stimulus (solid black, right ordinate scale) units [37], for two night shift nurses working in South Bend, IN, USA. Measurements were made continuously starting at 15:00 on 30 January 2006 until approximately 15:00 on 31 January 2006. Also shown are vertical photopic illuminances (dashed black, left ordinate scale) expected from outdoor exposure to a partly cloudy sky at the same location on the same date in open country for a 45° azimuth angle from the sun [26].