New methodological approaches in Reflectance Transformation Imaging applications for conservation documentation of cultural heritage metal objects

•Colour, texture and gloss can be used to characterise the visual appearance of a surface.•Proposed methodology for raw data processing of Reflectance Transformation Imaging (RTI) for the extraction of feature, saliency and distance measurement maps.•Resulting in automated mapping for condition assessment and monitoring conservation-restoration treatments.•Application of the methodology on a late-Roman bronze coin.