MEETINGS FOR 2007-2008
Wednesday 5 MARCH 2008
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MEETINGS FOR 2007-2008 Wednesday 5 MARCH 2008 |
NEWTON
LECTURE
The
Use of Color Science in Art Conservation
in the Oliver Thompson
Lecture Theatre, City University, London at 14.00 hrs
Prof
ROY S. BERNS Rochester Institute of Technology,
Rochester, New York
The Use of Color Science in Art Conservation
The first Newton Medal recipient, Professor W. D. Wright, pioneered the use of color science in art conservation, specifically non-destructive and non-contact spectrophotometry. Twenty-five years later, digital imaging performs the same function with technologies ranging from a scanning single-pixel sensor coupled with a dispersing element to commercial high-resolution color-filter array digital cameras coupled with two optimized absorption filters. The latter approach has been used successfully in several museums. Six camera signals are mapped to spectral reflectance based on a training target and the inherent wide absorption bandwidths of colored materials within the visible spectrum. This is often referred to as multi-spectral, or simply, spectral imaging. Another application of color science, instrumental-based color matching, has been reduced to practice as an aid to art conservators when performing restorative in painting, also known as retouching. Using an optical database of candidate retouching materials derived from one or two samples per material and an appropriate color-mixing mathematical model, a subset is selected leading to the best match under multiple lighting conditions, that is, minimal illuminant metamerism. These two applications of color science have been combined to provide novel opportunities in the study of cultural heritage. The first is “digital rejuvenation.” In some cases, artist materials change over time resulting in undesirable color changes such as fading, darkening, and yellowing. It is possible to computationally replace these changed materials with temporally stable materials and synthesize images that indicate how the artwork may have appeared prior to the color changes. This has been achieved for paintings and drawings by Vincent van Gogh and Georges Seurat. The second is spatially mapping the colored materials and their concentrations comprising a work of art. Such maps provide new insight into an artist’s working method and can also be an aid to conservation treatments. This has been achieved for Vincent van Gogh’s The Starry Night.
Relevant
Publications:
R. S.
Berns, “Rejuvenating Seurat’s palette
using color and imaging science: A simulation,” in R. L.
Herbert, Seurat and the Making of La Grande
Jatte,
Art Institute of Chicago and University of California Press, 214-227,
2004.
R. S.
Berns, “Color accurate image archives
using spectral imaging,” in Scientific
Examination of Art: Modern Techniques in Conservation and Analysis,
National Academies Press, 105-119, 2005.
L. A.
Taplin and R. S. Berns, “Practical spectral
capture systems for museum imaging,”
Proc. 10th Congress of the International Colour
Association,
Granada, 1287-1290 (2005).
R. S.
Berns, L. A. Taplin, F. H. Imai, E.
A. Day, D. C. Day, “A comparison of small-aperture and
image-based
spectrophotometry of paintings,” Studies
in Conservation 50, 253-266 (2006).
R. S.
Berns and M. Mohammadi, “Evaluating
single- and two-constant Kubelka-Munk turbid media theory for
instrumental-based inpainting” Studies
in
Conservation, 52, 299-314 (2007).
Y.
Zhao and R. S. Berns, “Image-based
spectral reflectance reconstruction using the Matrix R
method,” Color Research and
Application, 32,
343-351 (2007).
Y.
Zhao and R. S. Berns, “An investigation
of multispectral imaging for the mapping of pigments in
paintings,” Proc. SPIE Electronic
Imaging Conf., in
press.
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