A simulation method to determine adaptation luminance is proposed for implementation of CIE mesopic photometry system. The simulation takes four factors into account; luminance distribution, eye movement of observers, surrounding luminance effect, and an area of measurement. Each factor is modelled as a function with respect to a spherical coordinate system of the field of view. By using the simulation method, an adaptation luminance for the area of measurement is determined through four calculation steps. The simulation method was applied to luminance distributions of outdoor lit scene examples and the results were compared with possible simple predictors for the adaptation luminance. The comparisons suggest that an average luminance of the area of measurement can be considered as a good approximation in most of cases. Exceptions are scenes for pedestrians in which there are many bright sources surrounding the area of measurement.
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