Analysis of the colorimetric properties of goniochromatic colors using the MacAdam limits under different light sources

Technological innovation in all areas has led to the appearance in recent years of new metallic and pearlescent materials, yet no exhaustive studies have been conducted to assess their colorimetric capabilities. The chromatic variability of these special-effect pigments may largely be due to the three-dimensional effect of their curved shapes and orientations when they are directionally or diffusely illuminated. Our study examines goniochromatic colors using the optimal colors (MacAdam limits) associated with normal colors (photometric scale of relative spectral reflectance from 0 to 1) under certain conventional illuminants and other light sources. From a database of 91 metallic and interference samples and using a multi-gonio-spectrophotometer, we analyzed samples with lightness values of more than 100 and others with lightness values of less than 100, but with higher chromaticities than optimal colors, which places them beyond the MacAdam limits. Our study thus demonstrates the existence of chromatic perceptions beyond the normal solid color associated with these materials and independent of the light source. The challenge for future research, therefore, is to replicate and render these color appearances in current and future color reproduction technologies for computer graphics.

Number of discernible colors for color-deficient observers estimated from the MacAdam limits

We estimated the number of colors perceived by color normal and color-deficient observers when looking at the theoretic limits of object-color stimuli. These limits, the optimal color stimuli, were computed for a color normal observer and CIE standard illuminant D65, and the resultant colors were expressed in the CIELAB and DIN99d color spaces. The corresponding color volumes for abnormal color vision were computed using models simulating for normal trichromatic observers the appearance for dichromats and anomalous trichomats. The number of colors perceived in each case was then computed from the color volumes enclosed by the optimal colors also known as MacAdam limits. It was estimated that dichromats perceive less than 1% of the colors perceived by normal trichromats and that anomalous trichromats perceive 50%–60% for anomalies in the medium-wavelength-sensitive and 60%–70% for anomalies in the long-wavelength-sensitive cones. Complementary estimates obtained similarly for the spectral locus of monochromatic stimuli suggest less impairment for color-deficient observers, a fact that is explained by the two-dimensional nature of the locus.

Manuel Martínez Torres. Retrat d'un que s'enamorà del dibuix i dels colors

Parte del catálogo de la exposición celebrada en Elche del 12 de Abril al 10 de Mayo de 2002.

Pràctica 5: Coeducació

Coeducar significa «educar les persones al marge dels rols i els estereotips que ens imposa la societat, de manera que tinguen les mateixes oportunitats i no se’ls imposen diferències socioculturals (joguets, colors, formes de comportar-se, etc.) per ser home o dona». Per aquest motiu, coeducar no és educar a les mateixes aules els xiquets i les xiquetes, sinó propiciar un canvi en la cultura de l’escola infantil. Aquest canvi es basa a tenir cura de les relacions quotidianes a l’escola infantil, promovent una educació afectiva que afavorisca les relacions en igualtat i rebutge la violència, els prejudicis i els comportaments sexistes des d’edats primerenques i promoga la resolució pacífica de conflictes. Amb aquesta pràctica intentarem mostrar una experiència educativa que promoga la igualtat de gènere en l’alumnat d’educació infantil.

An algorithm to hide information in binary images

The objective of this paper is to develop a method to hide information inside a binary image. An algorithm to embed data in scanned text or figures is proposed, based on the detection of suitable pixels, which verify some conditions in order to be not detected. In broad terms, the algorithm locates those pixels placed at the contours of the figures or in those areas where some scattering of the two colors can be found. The hidden information is independent from the values of the pixels where this information is embedded. Notice that, depending on the sequence of bits to be hidden, around half of the used pixels to keep bits of data will not be modified. The other basic characteristic of the proposed scheme is that it is necessary to take into consideration the bits that are modified, in order to perform the recovering process of the information, which consists on recovering the sequence of bits placed in the proper positions. An application to banking sector is proposed for hidding some information in signatures.

Color representation and interpretation of special effect coatings

A representation of the color gamut of special effect coatings is proposed and shown for six different samples, whose colors were calculated from spectral bidirectional reflectance distribution function (BRDF) measurements at different geometries. The most important characteristic of the proposed representation is that it allows a straightforward understanding of the color shift to be done both in terms of conventional irradiation and viewing angles and in terms of flake-based parameters. A different line was proposed to assess the color shift of special effect coatings on a*,b*-diagrams: the absorption line. Similar to interference and aspecular lines (constant aspecular and irradiation angles, respectively), an absorption line is the locus of calculated color coordinates from measurement geometries with a fixed bistatic angle. The advantages of using the absorption lines to characterize the contributions to the spectral BRDF of the scattering at the absorption pigments and the reflection at interference pigments for different geometries are shown.

Global color estimation of special-effect coatings from measurements by commercially available portable multiangle spectrophotometers

Colors of special-effect coatings have strong dependence on illumination/viewing geometry and an appealing appearance. An open question is to ask about the minimum number of measurement geometries required to completely characterize their observed color shift. A recently published principal components analysis (PCA)-based procedure to estimate the color of special-effect coatings at any geometry from measurements at a reduced set of geometries was tested in this work by using the measurement geometries of commercial portable multiangle spectrophotometers X-Rite MA98, Datacolor FX10, and BYK-mac as reduced sets. The performance of the proposed PCA procedure for the color-shift estimation for these commercial geometries has been examined for 15 special-effect coatings. Our results suggest that for rendering the color appearance of 3D objects covered with special-effect coatings, the color accuracy obtained with this procedure may be sufficient. This is the case especially if geometries of X-Rite MA98 or Datacolor FX10 are used.

Stabilizing and Modulating Color by Copigmentation: Insights from Theory and Experiment

Natural anthocyanin pigments/dyes and phenolic copigments/co-dyes form noncovalent complexes, which stabilize and modulate (in particular blue, violet, and red) colors in flowers, berries, and food products derived from them (including wines, jams, purees, and syrups). This noncovalent association and their electronic and optical implications constitute the copigmentation phenomenon. Over the past decade, experimental and theoretical studies have enabled a molecular understanding of copigmentation. This review revisits this phenomenon to provide a comprehensive description of the nature of binding (the dispersion and electrostatic components of π–π stacking, the hydrophobic effect, and possible hydrogen-bonding between pigment and copigment) and of spectral modifications occurring in copigmentation complexes, in which charge transfer plays an important role. Particular attention is paid to applications of copigmentation in food chemistry.

Em busca da originalidade do patrimônio cultural na cidade-espetáculo: o caso da Casa Boehm em Joinville/SC

Este trabalho tem o intuito de discutir como um imóvel tombado na cidade de Joinville/SC vem respondendo ao mundo das influências contemporâneas da espetacularização. A Casa Boehm, hoje uma loja de calçados no comércio, foi construída em 1927 e tombada em 2001, por meio do Processo de Tombamento PFCC n. 627/003, de 10 de abril de 2000, homologado pelo Decreto n. 3.461/2001, do Governador do Estado, na época, Esperidião Amin. O imóvel vem sofrendo alterações físicas, que afetam princípios de unidade, volumetria, padrões de estilo arquitetônico, o que faz com surjam debates a respeito dos seus valores estéticos. A depender do gosto dos locatários, especialmente no que se referee às cores externas, sem autorização, vislumbra-se a partir da opinião dos participantes do Conselho de Patrimônio da cidade - COMPHAAN, a espetacularização que este bem vem suportando em nome de uma sociedade de consumo, que apenas visa o lucro, apesar de inúmeros debates teóricos acerca da preservação. Desta forma, quando se pensa em restauração de um patrimônio cultural edificado, a preocupação imanente é com a sua imagem subjetiva/simbólica, e ainda, não menos importante, no que se refere às cores utilizadas nas pinturas das edificações. A metodologia utilizada é qualitativa, por meio de pesquisa bibliográfica, documentais no Arquivo Histórico de Joinville – AHJ e na Fundação Cultural de Joinville – FCJ e, etnográfica. A etnografia, com nuances interdisciplinares, foi realizada nestes mesmos Arquivos da cidade de Joinville, nos arredores do bem em questão e analisando algumas impressões obtidas nas reuniões do Conselho de Patrimônio da cidade – COMPHAAN. Este estudo é parte integrante da pesquisa para doutoramento em Ciências Humanas, na Universidade Federal de Santa Catarina – UFSC. Parte-se da hipótese inicial de que as discussões que envolvem as cores em bens tombados têm se relacionado com a autenticidade e a integridade dos conjuntos nos centros históricos. Porém, vai além, já que o espetáculo buscado pelos gestores públicos, com intento de valorizar suas cidades, acaba por homogeneizar esses territórios em torno de uma ideia de patrimônio que tem sido questionada por alguns teóricos.