This report shows the results of the interlaboratory comparison carried out using dedicated RM (described in D3 document) and a description of the software for uncertainty calculation. Intercomparison protocol, software guidelines and data overview are in the Appendixes. The intercomparison highlights the need of deeper investigation on the measurement model and instrument performances: as it is the first exercise on a comparison on luminance coefficient measurement capabilities, the easiest

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... roach in the definition of measurement uncertainty was followed. The analysis of the Degree of Equivalence of the data, highlights the need of the LUMCORUN software and of a deep metrological evaluation of measuring devices. The data have a very low compatibility level even if the repeatability of the measurements of each laboratory is very high. So, the use of the standard deviation of the mean of the measurements is a poor estimator of the measurement uncertainty, and the impact of correlations among measurement geometries and instruments characteristics plays the most relevant role.