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This paper describes an experiment for assessing the discomfort glare caused by light emitting diodes (LEDs) having different colours. The results showed that coloured LEDs induce more discomfort glare than a white LED. On comparing different coloured LEDs, blue ones gave the highest glare perception, especially for those having shorter peak wavelengths. Different earlier proposed luminous efficiency functions for discomfort glare were applied to re-define luminance. This led to modified unified glare ratings, which achieved very accurate predictions of the visual results. A modified brightness based on a colour appearance model for unrelated lights was used to predict glare and also performed very well. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the agreement between multiangle appearance data obtained from multiangle measurements and the rating scores given by observers in terms of sparkle and coarseness. The metallic emotional equation for coloured metallic paints was developed on the basis of two experimental results. Experiment 1 involved measuring metallic paint appearance, and a multiangle spectrophotometer was used for measuring the appearance parameters of metallic coating samples under multiple measuring angles. In Experiment 2, observers were asked to visually assess coloured metallic samples under directional and diffuse light conditions. The observers assessed the test samples, illuminated from the top, from three observation angles. Principal component analysis was performed to analyse the observers’ emotional responses. Finally, the metallic emotional models consisting of the expensiveness model and fashion model were constructed. [ABSTRACT FROM AUTHOR]

In a typical Euclidean three-dimensional colour space such as CIELAB, the 'third-dimension', such as CIELAB chroma, has long been criticized as being confusing and difficult to understand for naïve observers and it had relatively poor consistency in visual assessments. As an attempt to find a promising replacement to existing 'third-dimension', two psychophysical experiments were conducted in this study using naïve observers. In the first experiment, 24 Korean observers assessed 48 NCS colour chips in terms of bright, light-heavy, active-passive, fresh-stale, clean-dirty, clear, boring, natural-not natural, warm-cool, intense-weak, saturated, vivid-dull, distinct-indistinct, full-thin and striking. According to experimental results, 'saturated' and 'vivid-dull' were found to highly correlate with CIELAB chroma and were thus regarded as good candidates to become alternatives to existing 'third-dimension'. In the second experiment, 40 Korean and 68 British observers assessed more than 100 samples in terms of saturation, vividness, blackness and whiteness. Thus, observers assessed 120 samples for saturation, vividness and whiteness. For blackness, 110 samples were assessed. In both experiments, the colour samples were presented in a viewing cabinet and assessed individually. Principal component analysis identified two components that were associated with CIELAB lightness and chroma. In general, there was a similarity between the visual results of the British and Korean observers. High correlation coefficients were found for the following comparisons: predicted values of Berns' depth model versus the present 'saturation' response; Berns' clarity versus 'vividness' response; Berns' vividness versus 'blackness' response; and CIELAB lightness versus 'whiteness' response. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 203-215, 2017 [ABSTRACT FROM AUTHOR]

The CIE color rendering (fidelity) index (CRI) has remained unchanged for over four decades. Most, if not all, of its components could be updated to more state-of-the-art methods. One of the most critical components of any color rendering (fidelity) metric is the test sample selection. This article therefore addresses the importance of uniform sampling of wavelength space to avoid selective optimization—that is, taking advantage of the unequal contributions of different wavelength regions to the general color rendering score—of light source spectral power distributions. It summarizes the development of a mathematical sample set with undistorted spectral sensitivity, the HL17 set. The set is used in a recently proposed update, the CRI2012 general color rendering index. To assess the impact of the spectrally uniform sample set on color fidelity scores, the CRI2012 index values for each of a set of 139 lamps were compared with those of the CIE CRI. In addition, the impact of updating the other components was investigated. A mean and maximum absolute difference of respectively 5.9 and 21.8 index units were found between the CRI2012 and CIE CRI, although the largest part—respectively 4.03 and 19.7 index units—was shown to be the result of updating the color difference engine and the switch to the CIE 10° observer. The analysis also indicated possible past spectral selective optimization of some warm-white tri-band fluorescent sources for high luminous efficacy of radiation (LER) and (just) sufficient CIERavalues by taking advantage of the spectral nonuniformity of the CIE reflectance set. Adopting a spectrally uniform sample set in a color rendering metric therefore has important practical implications when designing light source spectra. Finally, possible updates and further improvements of the CRI2012 are briefly mentioned. [ABSTRACT FROM PUBLISHER]