Calibration with Macbeth color charter for noninvasive technical photography of the fifteenth century wall painting cycle by Filippo Lippi in the Cathedral of Prato by Alfredo Aldrovandi and Annette Keller (Opificio delle Pietre Dure). The photography of the UV fluorescence indicates areas containing organic materials. However not fluorescing areas may also contain organic materials mixed with pigments able to quench the visible fluorescence. Photo: F. Piqué.