Pulsed thermography and infrared reflectography: comparative results for underdrawing visualization in paintings

Reflectographic analyses applied on paintings can be performed using cameras equipped with different detectors with different abilities in detecting and visualizing underdrawings, repainting, restorations, and other nonvisible information. In this research, the results obtained through thermographic imaging followed by statistical imaging postprocessing methods have been compared with those obtained with traditional reflectographic methods in the short-wave infrared range. The comparison has been performed studying the thermal sequence after a single pulse of light with a different spectrum of ad hoc mock-ups. Results showed that for limited cases, signal-to-noise ratio seems to be more relevant in obtaining reliable images of underdrawings with respect to the effect of optical absorption of visible light by painting layers.