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Proceedings Paper

Post-capture data analysis as an aid to the interpretation of ultraviolet-induced fluorescence images
Author(s): Giovanni Verri; Daniela Comelli; Sharon Cather; David Saunders; Francesca Piqué
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Paper Abstract

Although digital multispectral imaging-particularly ultraviolet-induced fluorescence imaging-is a very common examination tool, its interpretation remains fraught with difficulties. Interpretation is strongly dependent on the capture methodology, requires an understanding of the physical and chemical characteristics and interactions among materials in artworks and is affected by data-analysis procedures. The present research, which began with imaging of paint materials of known composition and proceeded to a range of representative case studies, confirmed that fluorescence emissions by painting materials-such as organic binders or colorants-are generally severely affected by the presence of absorbing non-fluorescing materials, such as inorganic pigments. Application of a mathematical model based on the Kubelka-Munk theory, resulted in the possibility of distinguishing between real and apparent fluorescence emissions. Real emissions correspond to the presence of materials which de facto exhibit fluorescent properties (typically organic binders and colorants), while apparent emissions relate to the optical interactions among fluorescent materials and surrounding non-fluorescent materials (typically inorganic pigments). Correction for the 'pigment-binder interaction' can also provide useful information on the presence of materials whose fluorescence is almost obliterated by absorbing pigmented particles. Therefore, this image-processing methodology can be used to characterise and reveal emissions that are dimmed or altered by re-absorption. This capacity to reveal the presence of weakly fluorescing emitters has important conservation implications and informs the sampling strategy for further analytical investigations. Examples of the application of this data analysis to images made at the Grotto Site in Dunhuang, China, and at the British Museum are presented.

Paper Details

Date Published: 18 March 2008
PDF: 12 pages
Proc. SPIE 6810, Computer Image Analysis in the Study of Art, 681002 (18 March 2008);
Show Author Affiliations
Giovanni Verri, The Getty Conservation Institute (United States)
Courtauld Institute of Art (United Kingdom)
Daniela Comelli, Politecnico di Milano (Italy)
Sharon Cather, Courtauld Institute of Art (United Kingdom)
David Saunders, The British Museum (United Kingdom)
Francesca Piqué, The Getty Conservation Institute (United States)

Published in SPIE Proceedings Vol. 6810:
Computer Image Analysis in the Study of Art
David G. Stork; Jim Coddington, Editor(s)

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