The ability to digitally remove the varnish layer during the pre-conservation diagnostic of a painting, without any chemical or physical intervention, could be an advantage because it enables the prediction of the outcome of the cleaning procedure of the protective layer and contributes to the treatment proposal. Two paintings from Adriano de Sousa Lopes were investigated by hyperspectral imaging in the visible range, before and after the varnish layer removal. The spectral reflectance was estimated in each case and its comparison used to assess the effect of the varnish layer removal. The simulated paintings with the old varnish layer were compared with those restored, with no varnish, by comparing the chromaticity coordinates and other chromatic descriptors. It was found that considering the effect of the varnish layer of each painting individually produces lower errors than considering the average of the varnish layer across paintings. It was also found that simulating the varnish layer removal without knowing the varnish transmittance produces limited results and that the errors are smaller if the chromatic content is assessed without considering lightness.
RGB digital cameras (RGB) compress the spectral information into a trichromatic system capable of approximately representing the actual colors of objects. Although RGB digital cameras follow the same compression philosophy as the human eye (OBS), the spectral sensitivity is different. To what extent they provide the same chromatic experiences is still an open question, especially with complex images. We addressed this question by comparing the actual colors derived from spectral imaging with those obtained with RGB cameras. The data from hyperspectral imaging of 50 natural scenes and 89 paintings was used to estimate the chromatic differences between OBS and RGB. The corresponding color errors were estimated and analyzed in the color spaces CIELAB (using the color difference formulas ΔE*ab and CIEDE2000), Jzazbz, and iCAM06. In CIELAB the most frequent error (using ΔE*ab) found was 5 for both paintings and natural scenes, a similarity that held for the other spaces tested. In addition, the distribution of errors across the color space shows that the errors are small in the achromatic region and increase with saturation. Overall, the results indicate that the chromatic errors estimated are close to the acceptance error and therefore RGB digital cameras are able to produce quite realistic colors of complex scenarios.
The present article intends to present a model for the documentation and registry used in the diagnosis and intervention stages in conservation and restoration (C&R) of a set of twelve works by Adriano de Sousa Lopes, from the collection of the Faculty of Fine Arts, University of Lisbon (FBAUL). To this end, a free and open access geographic information system (GIS) software called QGIS® was used. During the analysis, several vector maps were produced, both for diagnosis and for conservation and restoration treatments (CR), namely the microcracks network, areas of loss, consolidation areas, textile microsurgery and chemical cleaning. The quantitative results obtained from the spatial analyses of the pictorial surfaces were recorded in the GIS database. Finally, it was verified that the technical study of works with the QGIS(R) program contemplates a spatial perception of the works of art for evidencing, in a systematic and integrated way, the phenomena of alteration of the pieces under analysis.
A reintegração cromática de uma pintura é sempre um desafio para os conservadores-restauradores e a decisão de como reintegrar é geralmente baseada no valor e na função das obras. Porém, a escolha de qual a técnica de reintegração é a mais adequada nem sempre é fácil de se justificar. Para tentar ajudar a dar resposta a esta questão foi utilizado um software de Sistema de Informação Geográfica (SIG), designado de QGIS®. Através da edição vetorial foram efetuados vários mapas temáticos com a finalidade de registar as lacunas que se observavam nas pinturas. A análise efetuada com o auxílio do SIG permitiu fazer a caracterização espacial das lacunas em área, para facilitar a tomada de decisão da técnica de reintegração a ser aplicada. Como caso de estudo utilizou-se uma pintura académica de Adriano de Sousa Lopes (1879-1944). Na reintegração cromática usaram-se três técnicas conhecidas de conservação e restauro: o processo mimético, a selezione cromatica e o pontilhismo.
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