Lighting is no longer just turning on a lamp. Solid State Lighting allows reaching high energy savings and visual perception, but the path to success was not easy: in the early years when LED were available on the market, several concerns slowed down their widespread implementation. The large spread of Lighting Systems based on LED arrived only when products quality increased thanks also to the development of new metrology paradigms able to certify LED performances peculiarities. Currently LED promises to widespread in every lighting application increasing not only energy savings, but night-time safety, health and wellbeing thanks to lighting systems based on connectivity and smart controls, but new design paradigms and metric headed to new objectives are necessary, therefore there will be no need to measure only energetic and light performances. We are moving toward an approach more sensitive to Human Needs: energy savings and light efficiency are of no more the only interest to focus on, we need to measure performance of a lighting system in terms of not only SI quantities. We need now a consolidated metrology and design approach to Smart System for complexity and suitable to compare lighting quality in term of human perception and wellbeing.
The archaeological cloth known as the Shroud of Turin is a controversial object for both scientific and religious reasons. After a brief introduction on the scientific data about the age of the cloth and the microscopic complexity of the images embedded on it, we discuss the unique reddish color of blood stains on the Shroud, which caught the attention of several scholars in the last decades. Various hypotheses were proposed to explain the blood stains reddish color, and the experimental tests produced uncertain results because data were not sufficient or were obtained in vitro. We have tested the strength of two hypotheses, namely, the long term influence of ultraviolet (UV) light on high-bilirubin blood and the presence of carboxyhemoglobin, respectively by RGB color analyses of high-bilirubin blood after irradiation by ns excimer laser pulses and UV lamp and by the study of the spectral reflectance of the blood stains on the Shroud.
Interdependence between color and gloss is a concept well-known by artists, especially by old masters, but is not usually considered in material characterization. Indeed, measurement methods and definitions consider these two attributes individually. This research investigates how the available measurement methods for gloss and color (saturation) fit with corresponding perceptual qualities, glossiness and saturation. The definitions of both measured quantities, as well the measurement methodologies, were developed for reference materials (ceramic tiles for color and dark glass specimen for gloss) not representative of artwork materials and do not consider observation conditions similar with those adopted during exhibitions. The prediction of material appearance is recognized as one of the most important challenges in applied metrology, because appearance is the key to achieve effective exhibitions and consumers choices. The results of this study highlight that the two perceived qualities are mutually related, as well the measured quantities: gloss and saturation mutually interfere and the measurement methods and quantities are not uniform with the perceived qualities and the colorimetric coordinate C* no longer describes the perceived saturation.
The aim of this study is to evaluate experimentally how well available metrics are able to evaluate how lighting sources affect the perception of visual attributes of artworks exhibited, providing useful indications for works of art exhibition designers. The study considers objective investigations on optical material properties (i.e. spectral reflection factor) compared to subjective tests on colour attributes evaluation of artworks lighted by common lamps (incandescent and fluorescent lamps) and LED lighting sources.
Commission International Eclairage (CIE) developed several mathematical methods to predict colour rendering of lighting source, as well visual attributes of materials, but are only an approximation of the material appearance: too many parameters of influence, subjects expectancy included, influence the appearance. In artwork exhibition visual appearance is of fundamental importance and currently no reliable and robust appearance model is available. Comparing objective evaluations and subjective results for lighting set up comparable to works of art exhibition, will provide useful indications on the applicability of colorimetric calculation to artwork exhibition when LED are involved.
Visual attributes (hue, saturation, brightness…) of six different colours under LED and not-LED sources at the same Correlate Colour Temperature were compared to the associate objective characteristics calculated from the spectral reflectance.
The results show that the perception of visual attributes differs from objective data when SSL sources are involved and when colours are perceived in complex samples: in some cases the visual system is not coherent with the suggestions arising from the calculations.
The paper presents an investigation on the correlation between spectral characteristics and conservation conditions of parchment to define a NON invasive methodology able to detect and monitor deterioration process in historical parchment without the need of taking small samples. To verify the feasibility and define the most appropriate measurement method, several samples of contemporary parchments, produced following ancient recipes and coming from different animal species, with different degrees of artificially induced damage, were analyzed. The SRF and STF of each sample were measured in the same point, before and after each step of the artificial ageing treatment. Having at disposal a parchment coming from a whole lamb leather, allowed also the study of the correlations between the variations of SRF – STF and the intrinsic factors of a parchment like the variability of animal skin anatomy and of manufacturing. Analyzing different samples allowed also the definition of the measuring method sensitivity and of reference spectrum for the different animal species parchments with accuracy limits. The definition of a reference spectrum of not damaged parchment with acceptability limits is a necessary step for understanding, through SRF – STF measurements, historical parchments conservation conditions: indeed it is necessary to know if deviations from the reference spectrum are ascribable to damage or only to parchment anatomic/production variability. As a case study, the method has been applied to two historical parchment scrolls stored at the Archivio di Stato di Torino (Italy). The SRF - STF of both scrolls was acquired in several points of the scroll, the average spectrum of each scroll was compared with the reference spectra with the relative tolerance limits, recognizing the animal species and damage alterations and demonstrating the feasibility of the method.
The spectral reflectance of different samples of three different hues, (red, green, blue) with four different protective
varnishes was measured in 8/d condition and with a goniometer equipped with a spectrometer. The samples are
representative of hue and varnishes typically used in works of arts, the characterization was performed to test how the
different gloss finishing induced by transparent varnishes affect the spatial distribution of the luminance coefficient in
typical lighting arrangements for exposition of works of art. Nowadays the most used transparent protective varnishes
are matt or glossy, natural or synthetic. The choice within them is usually made looking at mechanical, chemical (also in
term of removal) and protective properties. Varnishes optical properties investigation on saturation and gloss alteration
of the perceived artifacts are not usually investigated. Expected results of this research include: analysis of influences on
color appearance of protective varnish according to the condition of illumination and observation, suggestion of new
additional criteria for varnish selection and lighting set up exposition and reliability of 8/d measurements condition, that
is a typical measurement set-up of portable instruments. Our results showed that natural varnishes are more able to
change the gloss of the surfaces than synthetic ones, because the shape and intensity of the specular peak for glossy and
matt natural varnish are very different. Both synthetic and natural varnishes have different behaviors at 30° or 60° light
incidences: at 30° of incidence all samples have smaller variations, while at 60° of incidence the variations are larger,
and for some samples the achromatic point is reached.
The European Metrology Research Program (EMRP) is a metrology-focused program of coordinated Research and
Development (RD) funded by the European Commission and participating countries within the European Association
of National Metrology Institutes (EURAMET). It supports and ensures research collaboration between them by
launching and managing different types of project calls. Within the EMRP Call 2012 "Metrology for Industry", the joint
research project (JRP) entitled "Multidimensional Reflectometry for Industry" (xD-Reflect) was submitted by a
consortium of 8 National Metrology Institutes (NMIs) and 2 universities and was subsequently funded. The general
objective of xD-Reflect is to meet the demands from industry to describe the overall macroscopic appearance of modern
surfaces by developing and improving methods for optical measurements which correlate with the visual sensation being
evoked. In particular, the project deals with the "Goniochromatism", "Gloss" and "Fluorescence" properties of dedicated
artifacts, which will be investigated in three main work packages (WP). Two additional transversal WP reinforce the
structure: "Modelling and Data Analysis" with the objective to give an irreducible set of calibration schemes and
handling methods and "Visual Perception", which will produce perception scales for the different visual attributes.
Multidimensional reflectometry involves the enhancement of spectral and spatial resolution of reference
gonioreflectometers for BRDF measurements using modern detectors, conoscopic optical designs, CCD cameras, line
scan cameras, and modern light sources in order to describe new effects like sparkle and graininess/coarseness. More
information and updated news concerning the project can be found on the xD-Reflect website http://www.xdreflect.eu/.