Buscando la correlación instrumental y visual óptima para colores goniocromáticos mediante cabinas de iluminación y multi-gonio-espectrofotómetros

En la búsqueda de la modelización y cuantificación óptimas de la correlación instrumental y visual de materiales goniocromáticos (pinturas y plásticos, principalmente) en los procesos de control de calidad típicos del sector automovilístico, se presenta aquí una comparación de las prestaciones de diversos tipos actuales de instrumentos de medida del color y cabinas de iluminación. Los multi-gonioespectrofotómetros analizados fueron: Datacolor FX10®, X-Rite MA98® y BYK-mac®, y, las cabinas de iluminación direccional: gonio-vision-box® y byko-spectra effect®. Las propiedades ópticas, básicamente fotométricas y colorimétricas, evaluadas fueron: geometrías de medida, fuente de luz, distancia de observación y dirección visual a la muestra. Los resultados aportados mostraron que actualmente dicha correlación instrumental y visual no es óptima debido a desajustes en las cabinas.

Characterization of goniochromism: current status and pending challenges

Clase invitada impartida en marzo 2011 en la asignatura "Colour on industry" del máster Erasmus Mundus "Color in Informaticas and Media Technology" en la Universidad de Granada.

Capabilities and resources of the University of Alicante on color technology for automotive sector

Charla realizada en el pasado 1st BYK-Gardner Iberian Automotive Meeting, celebrado en Alicante, entre los días 13 y 14 de Octubre de 2011: http://web.csidiomas.ua.es/congresos/iberianautomotive/index.html

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.

Reproducibility comparison among multiangle spectrophotometers

New color-measuring instruments known as multiangle spectrophotometers have been recently created to measure and characterize the goniochromism of special-effect pigments in many materials with a particular visual appearance (metallic, interference, pearlescent, sparkle, or glitter). These devices measure the gonioapparent color from the spectral relative reflectance factor and the L*a*b* values of the sample with different illumination and observation angles. These angles usually coincide with requirements marked in American Society for Testing and Materials (ASTM) and Deutsches Institut Für Normung standards relating to the gonioapparent color, but the results of comparisons between these instruments are still inconclusive. Therefore, the main purpose of this study is to compare several multiangle spectrophotometers at a reproducibility level according to ASTM E2214-08 guidelines. In particular, we compared two X-Rite multi-gonio spectrophotometers (MA98 and MA68II), a Datacolor multi-gonio spectrophotometer (FX10), and a BYK multi-gonio spectrophotometer (BYK-mac). These instruments share only five common measurement geometries: 45° × −30° (as 15°), 45° × −20° (as 25°), 45° × 0° (as 45°), 45° × 30° (as 75°), 45° × 65° (as 110°). Specific statistical studies were used for the reproducibility comparison, including a Hotelling test and a statistical intercomparison test to determine the confidence interval of the partial color differences ΔL*, Δa*, Δb*, and the total color difference ΔE*ab. This was conducted using a database collection of 88 metallic and pearlescent samples that were measured 20 times without the replacement of all the instruments. The final findings show that in most measurement geometries, the reproducibility differences between pairs of instruments are statistically significant, although in general, there is a better reproducibility level at certain common geometries for newer instruments (MA98 and BYK-mac). This means that these differences are due to systematic or bias errors (angle tolerances for each geometry, photometric scales, white standards, etc.), but not exclusively to random errors. However, neither of the statistical tests used is valid to discriminate and quantify the detected bias errors in this comparison between instruments.

Experiences with an Object-Oriented, Multi-Stage Language

Metaphor is a multi-stage programming language extension to an imperative, object-oriented language in the style of C# or Java. This paper discusses some issues we faced when applying multi-stage language design concepts to an imperative base language and run-time environment. The issues range from dealing with pervasive references and open code to garbage collection and implementing cross-stage persistence.