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97 <br />adapting the size of the pupil to let in more or less light. For this reason, a given glare <br />source will seem more severe in dark surroundings than in lighter surroundings, since the <br />pupil is more dilated in the darkness. For a simple illustration of this principle, consider <br />that automobile headlights can give the perception of glare at night, but do not seem bright <br />when viewed in daylight. <br />For sports lighting, the brightness of the surroundings generally cannot be controlled. For <br />recreational fields, the surroundings generally are quite dark. The eyes' adaptation will be <br />based on the average luminance of the field and the dark sky. For an outdoor professional <br />stadium, the eye will be adapted to a higher average luminance, as the field generally has a <br />higher luminance (due to a higher illumination level), and due to part of the field of view <br />being filled by sea*Wspectators, instead of dark sky. <br />E. Number of Sources <br />The severity of the glare sensation will increase as the number of glare sources within the <br />field of view increases. <br />F. Time of Exposure <br />The severity of the glare sensation can be affected by the time of exposure. A glare source <br />that is not objectionable for short periods of time may become uncomfortable if viewed for <br />a long period of time. The human eye, just as other parts of the body, can become fatigued <br />by unfavorable conditions. <br />M. Human Factors that Affect the Perception of Glare <br />A. Age <br />With age, the lens of the human eye becomes thicker and increasingly opaque. As a result, <br />a portion of the light entering the eye is scattered randomly within the eye, instead of <br />forming a clear image on the retina. Therefore, older individuals are generally more <br />affected by glare than younger individuals. <br />B. Fatigue <br />Like other physiological processes, a person's vision can be affected by how rested or <br />fatigued that person is. Generally speaking, the more fatigued a person is, the more severe <br />a glare source will be perceived. For example, viewing the headlights of oncoming cars <br />may seem more severe in the evening when the viewer is tired than in the morning, when <br />the viewer is rested, even though the visual characteristics are equal. <br />The purpose of this document is to provide an educational reference for specific technical issues that affect the <br />quality and performance of a sports lighting system. <br />Prepared by: Mark DeJong <br />Draft date: 11 -Sept 02 <br />Released: 27- Sept -02 <br />Musco products referenced in this document are protected by one or more of the following U.S. patents: 4190881; 4374407; 4423471; <br />4450507; 4712167; 4725934; 4729077; 4816974; 4947303; 4994718; 5012398; 5075828; 5134557; 5161883; 5207747; 5211473; <br />5229681; 5313378; 5337221; 5343374; 5377611; 5398478; 5402327; 5423281; 5426577; 5519590; 5595440; 5600537; 5647661; <br />5707142; 5794387; 5856721; 5887969; 5906425; 5944413; D337168; D353797; 0353911; 13411096. Canada Patents: 70479; 74939; <br />1114798; 1181380; 2009749; 2009749; D73755; 2217872. MeAco Patent: 175863; 1697. Australia Patents: 670062; 708912. New <br />Zealand Patent: 246820. Europe Patent: 440531. Other patents pending. <br />#TB0025 <br />Page 2 of 2 <br />