FROM LEONARDO TO RAFFAELLO: INSIGHTS BY VIS-IR REFLECTOGRAPHY

Infrared reflectography is a precious tool in the examination of artworks as it allows the visualization of surface and subsurface features such as retouches, losses, and painting integrations, and more generally to reveal pentimenti and/or concealed underdrawings. For this indisputable value it is under a constant technological development. In our contribution, we exemplify the added value of the cutting-edge improvements in our optical scanning device on two Italian renaissance artworks by Leonardo da Vinci and Raffaello Sanzio. In brief, our device, specifically designed for in situ imaging of artworks, collects the backscattered radiation that is resolved both spectrally and spatially. The implementation of the laser-based autofocus, besides keeping the instrument at the correct working distance, enables the acquisition of the painting shape. The most recent achievement is the coupling of the visible module to the infrared one. It follows that the resulting instrument output is a multispectral hypercube consisting of a sequence of 32 monochromatic images that are aberration-free, metrically correct and calibrated. The hypercube can also be seen as a collection of punctual spectral responses, one per each image pixel, with resolution of 20-30 and 50-100 nm in visible and infrared region, respectively, covering the 400-2500 am range. By adequate processing of images, the regions of different spectral behaviour can be singled out in order to answer the open questions by experts in the art history and art conservation or to give hints for the further in-depth analyses by punctual measurements.