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- The preferred chromatic composition of unfamiliar paintings is similar to originalPublication . Nascimento, Sérgio M.C.; Linhares, João M.M.; João, Catarina A. R.; Amano, Kinjiro; Montagner, Cristina; Melo, Maria J.; Vilarigues, Márcia; Freitas, Maria Helena de; Alfaro, Catarina; Bailão, AnaThe aim of this work was to compare the preferred chromatic composition for unfamiliar paintings with the original. Stimuli were images of paintings generated by rotating the color volume around the L* axis in CIELAB color space. The images were presented on a CRT. Four paintings were abstract from Amadeo de Souza-Cardoso, two had figurative elements from the same painter, two were abstract and two were figurative from other painters. In each trial a painting selected at random from the set was presented with its color volume rotated by angle selected at random. The task of the observer was to adjust the angle of the chromatic rotation for best subjective impression. Three groups of observers carried out the experiment: 50 without previous knowledge of the paintings, 8 experts in art but unfamiliar with the paintings tested and 6 experts in the paintings of Amadeo de Souza-Cardoso. It was found that the distribution of angles selected for data pooled across paintings for the non-specialist observers could be described by a Gaussian function centred at -2 deg, i.e. close to the original colors of the paintings, and with a FWHM of 64 deg, just about 1.5 above the threshold to detect a chromatic change.
- Chromatic reintegration in contemporary monochromatic unvarnished paintings: a case study based on artwork from Jorge MartinsPublication . Aleixo, Marta; Bailão, Ana; Gomes, Andreia E.; Linhares, João; San Andrés, Margarita; Nascimento, SérgioThe choice of chromatic reintegration materials for contemporary monochromatic oil and acrylic emulsion unvarnished paints is usually a problem before treatment. This kind of paintings maybe subject to abrasions, especially on the edges, fingerprints and smudges, mainly caused during handling. Being unvarnished works, chromatic reintegration becomes a more complex process as no protective layer exist over the paint. The aim of this work was to assess the materials that over performed in the reintegration of paintings from the Portuguese painter Jorge Martins. Representative mock-ups made with the artist and using his materials and techniques were artificially aged. Different types of materials, aqueous and non-aqueous, were then tested to assess the best ones. It was found that the best results were obtained with Ferrario® pigment dispersed in the Tri-Funori® binding medium and with Winsor & Newton® Designers Gouache, both aqueous and non-toxic.
- Chromatic changes in paintings of Adriano de Sousa Lopes after the removal of aged varnishPublication . Linhares, João; Cardeira, Liliana; Bailão, Ana; Pastilha, Ruben; Nascimento, SérgioThe 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.
- II Colóquio “Investigações em Conservação do Património”Publication . Bailão, Ana
- Mapping lacunae for retouching paintings with computer graphics softwarePublication . Henriques, Frederico; Bailão, Ana; Bordalo, Rui; Gac, Agnès Le; Gonçalves, Alexandre; Cardeira, Liliana; Candeias, António; Vieira, EduardaThe objective of this paper is to present a workflow procedure to support the graphic recording of the operations performed during the retouching process involved in paintings. In this particular context, an orthophotography of a portrait painted on canvas from a university museum collection was used in Blender, a free and open-source 3D creation software suite. Blender uses an important metric coordination value, provided by the 3D workspace software that allows the areal characterization and numeric identification of each surface loss. The step-by-step procedure adopted to document and map lacunae in this artwork for subsequent retouching, is described.
- Mapeamentos com sistemas de informação geográfica (SIG) e seleção de critérios de reintegração cromática: pintura de Adriano de Sousa Lopes como caso de estudoPublication . Cardeira, Liliana; Bailão, Ana; Henriques, FredericoA 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 duas técnicas conhecidas de conservação e restauro: o processo mimético e o pontilhismo.
- Processamento de imagem digital (PID) como meio de análise, documentação e monitorização da corrosão do aço de carbono aplicado na escultura de Gonçalo JardimPublication . Alvarez, Ana Sofia; Linhares, João; Bailão, AnaO presente artigo pretende dar a conhecer um método de monitorização não invasiva do processo de corrosão da escultura de aço de Gonçalo Jardim, através do sistema de processamento de imagem digital. Esta investigação teve como principal objetivo desenvolver um algoritmo que faça o tratamento da informação de várias funções locais da morfologia da corrosão, através da extração de parâmetros quantitativos da imagem que exprimam essa informação. Para este efeito foi calculado o valor médio absoluto da entropia das imagens, que avalia a evolução da morfologia da corrosão da obra a longo prazo, de modo a documentá-la e analisar se há manutenção ou aumento da corrosão com o decorrer do tempo e, neste último caso, em que proporção.
- The “value-function" attributed to cultural heritage as a criterion for reconstruction or reintegration: the paintingsPublication . Bailão, Ana; Calvo, AnaThe intervention criteria applied to old objects and paintings in each historical period, in the treatment of reconstruction and reintegration of the form and the lost colours, has depended of the value-function attributed. The conservation and restoration processes applied in each period have relied on the values given to each type of goods. So it has been able to prevail the aesthetic, historical, documentary, or other values. To understand the history of interventions in the objects of the past it is necessary first understand the social and cultural bases that determine the criteria used at different times and in different cultures. Furthermore, the current criteria for reintegration are determined by the “values” that now we apply to different cultural objects, including paintings by their role or function at this time.
- How good are RGB cameras retrieving colors of natural scenes and paintings? — a study based on hyperspectral imagingPublication . Linhares, João M. M.; Monteiro, José A. R.; Bailão, Ana; Cardeira, Liliana; Kondo, Taisei; Nakauchi, Shigeki; Picollo, Marcello; Cucci, Costanza; Casini, Andrea; Stefani, Lorenzo; Nascimento, Sérgio Miguel CardosoRGB 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 ∆E* ab and CIEDE2000), Jzazbz, and iCAM06. In CIELAB the most frequent error (using ∆E* 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.
- O sistema das nove cores na reintegração cromática de bens culturaisPublication . Bailão, AnaA seleção das cores mais adequadas para realizar uma reintegração cromática não é normalmente uma questão fácil de resolver. Para utilizar uma paleta restrita, muitos conservadores-restauradores optam por usar as três cores primárias, percebendo a curto prazo que cada fabricante tem as suas cores primárias e que com cada conjunto de três cores-pigmento se obtêm uma gama limitada de tons. Normalmente, segundo a obra, são necessários matizes adicionais para obter tons fora desta gama. O objectivo deste estudo é fazer um levantamento dos conceitos da teoria da cor e propor um sistema alternativo, constituído por nove cores, dois amarelos, dois azuis, dois vermelhos, pelo branco, preto e ainda pela terra de sombra queimada. Nos diversos exercícios demonstrativos recorreu-se às aguarelas Artist´s Watercolours da marca inglesa Winsor&Newton.
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