Measuring the luminance of lanthanide-based coordination polymers under UV excitation is of prime importance for many technological applications. This study highlights that the quantum yield gives no information about the luminescence intensity of a solid-state compound. Indeed, compounds with high quantum yield can actually be poorly luminescent. Therefore, a brightness calculation or a luminance measurement are mandatory for a quantitative estimation of the luminescence intensity. The calculated brightness appears to be a convenient quantitative parameter for the estimation of the luminescence intensity in the infrared domain, in which luminance is senseless. It is also a useful parameter in the visible domain, but one must keep in mind that only compounds with similar colorimetric coordinates can be compared. For comparing the luminescence intensities of compounds that exhibit different emission colors, the luminance measurement seems to be the most efficient method. A home-made setup that allows this measurement with high reproducibility is described in detail. The luminance of several lanthanide-based coordination polymers with benzene-poly-carboxylate ligands is measured, and the results are compared with brightness and quantum yield measurements. A standard is suggested for calibration.