G0 Revisited as Equally Bright Reference Boundary

Brilliance and zero grayness (denoted as G0) and are two terms coined by Ralph Evans. Nayatani, Heckaman and Fairchild have done series of work to incorporate them into comprehensive color appearance models. In this work, those concepts were reexamined to scale lightness/brightness across the chromaticity diagram. Specifically, observers, mostly with a color science background, were asked to adjust the luminance of a color patch to appear with no grayness, or equivalently just about/cease to glow. The hypothesis was that lightness can be equalized across those chromaticities and the Helmholtz-Kohlrausch effect is automatically incorporated. This hypothesis was verified in a follow-up experiment where another group of observers completed paired comparisons of the brightness between the collected G0 results. The G0 task was also repeated under another two levels of adaption backgrounds, based on which different absolute brightness results for a given chromaticity might be derived. In addition, high correlations between the G0 results (as a perceptual boundary between appearance modes) and different physical gamut boundaries including MacAdam's optimal colors were found for possible computational proxies and ecologically meaningful implications.

Beyond colour gamuts: Novel metrics for the reproduction of photoreceptor signals

Colour gamuts describe the chromaticity reproduction capabilities of a display, i.e. its ability to reproduce the relative cone excitations from real-world radiance spectra. While the cones dominate “canonical” visual function (i.e. perception of colour, space, and motion) under photopic light levels, they are not the only photoreceptors in the human retina. Rods and melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs) also respond to light and contribute to both visual and non-visual light responses, including circadian rhythms, sleep-wake control, mood, pupil size, and alertness. Three-primary display technologies, with their focus on reproducing colour, are not designed to reproduce the rod and melanopsin excitations. Moreover, conventional display metrics used to characterize three-primary displays fail to describe the display’s ability (or inability) to reproduce rod and melanopsin excitations, and thus do not capture the display’s ability to reproduce the full human physiological response to light. In this paper, three novel physiologically relevant metrics are proposed for quantifying the reproduction and distortion of the photoreceptor signals by visual displays. A novel equal-luminance photoreceptor excitation diagram is proposed, extending the well-known MacLeod-Boynton chromaticity diagram, to allow visualizations of the five-dimensional photoreceptor signal space in a three-dimensional projection.

EVALUATING SMARTPHONES COLOR FIDELITY AND METRIC ACCURACY FOR THE 3D DOCUMENTATION OF SMALL ARTIFACTS

<p><strong>Abstract.</strong> Smartphone camera technology has made significant improvements of sensors quality and software camera performance in recent years. Devices as Apple iPhone X and the Samsung Galaxy S9 Plus, allow to reach levels of image resolution, sharpness and color accuracy very close to prosumer SLR cameras, enabling also on-the-fly processing and procedures which were considered impossible to achieve until a few years ago. Starting from these premises, a series of issues and opportunities concerning smartphone application to artifacts documentation will be discussed. In particular, consistency and reliability of both shape and color representation achievable for small-medium artifacts belonging to exhibitions and museum collections. A low-cost, easy-to-use workflow based on low-cost widespread devices will be compared to consolidated digitization pipelines. The contribution focus is based on color accuracy of textured models achievable through smartphones by means of an internally developed application for the achievement of highly reliable developments of raw formats (.DNG) from Apple iPhone X. Color consistency will be calculated in terms of the mean camera chroma relative to the mean ideal chroma in the CIE color metric (&amp;Delta;E*₀₀) as defined in 2000 by the CIE on the CIEXYZ chromaticity diagram.</p>

Categorisation of Colour Terms Using New Validation Tools: A Case Study and Implications

This article elaborates on the results of a field experiment conducted among speakers of the Chakali language, spoken in northern Ghana. In the original study, the Color-aid Corporation Chart was used to perform the focal task in which consultants were asked to point at a single colour tile on the chart. However, data from the focal task could not be analysed since the Color-aid tiles had not yet been converted into numerical values set forth by the Commission internationale de l’éclairage (CIE). In this study, the full set of 314 Color-aid tiles were measured for chromaticity and converted into the CIE values at the Daylight Laboratory of the Norwegian University of Science and Technology. This article presents the conversion methodology and makes the results of the measurements, which are available in the Online Appendix. We argue that some visual-perception terms cannot be reliably ascribed to colour categories established by the Color-aid Corporation. This suggests that the ideophonic expressions in the dataset do not denote ‘colours’, as categorised in the Color-aid system, as it was impossible to average the consultants’ data into a CIE chromaticity diagram, illustrate the phenomena on the Natural Colour System (NCS) Circle and Triangle diagrams, and conduct a statistical analysis. One of the implications of this study is that a line between a visual-perception term and a colour term could be systematically established using a method with predefined categorical thresholds.

Triaryl-1,4-diamine-based polysquaraines: effect of co-solvent and monomer insertion on optoelectronic properties

Emission of the synthesized polysquaraine (left) and CIE 1931 color space chromaticity diagram of the corresponding OLED (right).