The aim of this study was to check the calculation model of the visibility levels using hemispherical targets, developed by Lecocq (see this issue(1)). We have compared the results of this new model with the appraisal ratings given by observers. The experiment confirms the reliability of calculations of the visibility levels thus obtained. The correlation between visibility level and observers' rating is high. We have compared these results with those found using flat targets. The study shows that it is possible to use both calculation models of visibility levels, which are thus both valid. However, they do not give the same result in terms of visibility for the same lighting geometry.
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