The Role of Scale Adjustment in Color Change Evaluation

Abstract

The aim of this research work was to assess the influence of different scale adjustment conditions on both color measurement and color difference quantification and, in particular, to determine the best procedure to follow for a high-reliability protocol. This issue is very important in the Cultural Heritage field and, above all, in color measurement, which is carried out at different times during conservation and restoration campaigns or during archaeological excavations. Color change evaluation, performed by way of spectrophotometric measurements under different scale adjustment procedures on selected samples represented by colored reflectance standards and colored paintings, aimed to obtain results not only on ideal samples (certified standards) but also on real case studies (paintings). The study was conducted by focusing on the coordinates of the CIELAB color space and, in particular, on the calculation of the ΔE*ab quantity. The results show the introduction of nonsystematic variation with different scale adjustment procedures independent of materials and hue.

Effect of water in color changes of historical paintings

“…The results are related to the D65 illuminant and the CIE 1964 standard colorimetric observer (10° standard observer). The scale adjustment was performed using the white calibration plate (CM‐A145) as a target for the maximum lightness and the device CM‐A32 for the minimum lightness 43 . The data elaboration, regarded as SPEX/100 values (SPecular component EXcluded and UV included), is performed by a dedicated software (SpectraMagic).…”

A method to improve the color rendering accuracy in cultural heritage: preliminary results

“…The objects have been realized with coloured cardboard supplied by Fabriano. The 3D samples have been acquired in a controlled environment, within a CAC equipped with D65 and F11 simulators [12] as suggested by the Commission International de l'Eclairage (CIE) [13]. The 3D scanner used is Konika Minolta Vivid 9i using the middle lens whose focal length is 14mm.…”

Effect of ionizing radiation on the colorimetric properties of PVA-GTA Xylenol Orange Fricke gel dosimeters

“…The selected illuminant, in fact, is denoted by the D that stands for daylight and the number 65 specifying the correlated color temperature expressed in kelvin and divided by 100. The scale adjustment, fundamental in colorimetry practice [50], was performed by the black (0%) and the white calibration (100%) references with which the instrument is equipped. The color measurements were carried out at different times on the same set of irradiated gels in order to check any changes due to the auto-oxidation process.…”