![]() ![]() (For small or large light sources outside the limits of applicability for UGR, alternative methods are available in CIE 2002 ). However, as a pragmatic solution that has been shown to work in the majority of situations over time the value of the methodology has been demonstrated. It also uses defined limiting criteria that relate to an observer positioned against the wall of a rectangular room looking in a specific direction, as opposed to sitting at a desk in a specific location within the room. It is limited to light sources which have a maximum subtense at the eye of between 0,0003 sr and 0,1 sr. The UGR methodology has acknowledged limitations. Lb is the general field luminance controlling the adaptation level of theįigure 1: Example lighting installation with poor glare control About the Limitations of the UGR Method ![]() P is the position index, which depends on the angular position of the source Ω is the solid angle subtended by the source at the observer's eye Ls is the source luminance in the direction of the observer Where the summation is over all sources in the field of view and where. The standard formula is shown in Equation 1 below. It allows us to evaluate the perceived discomfort glare from lighting installations such as that shown in figure 1. The Unified Glare Rating (UGR) methodology for calculating indoor discomfort glare, as given in CIE 1995 and CIE 2010 is well established and used internationally in many standards and codes of practice. ![]()
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