Diversidade cromática de cenários complexos digitalizados com imagiografia hiperespectral

Tese de doutoramento em Ciências (área do conhecimento em Física)Os métodos utilizados presentemente na avaliação da qualidade de fontes luminosas apresentam grandes limitações, em particular, com o aparecimento de fontes luminosas baseadas em LEDs. Alguns dos métodos até agora apresentados (“Colour Rendering Index” - CRI, “Gamut Area Index” - GAI ou o “Colour Quality Scale” - CQS) incluem parâmetros que vão para além da capacidade de reprodução das cores, como, por exemplo, a diversidade cromática que são capazes de gerar. Apesar da diversidade de índices, estes não estão orientadas para a estimativa da diversidade cromática em cenários complexos. Além disso, estão vocacionados para observadores normais, não contemplando observadores com deficiências da visão das cores. O objectivo deste trabalho é estimar a diversidade cromática em cenas naturais complexas a partir de dados obtidos por imagiografia hiperespectral e utilizar imagens hiperespectrais de cenários naturais, pinturas artísticas e cenários de interior para estimar a influência da distribuição espectral de diferentes iluminantes na diversidade cromática de cenários complexos, para observadores normais e deficientes da visão das cores. Pretende-se assim propor um índice que permita auxiliar na escolha de iluminantes com aplicação específica. Verificou-se que a diversidade cromática de cenas naturais é substancialmente inferior à prevista pelo volume do sólido de cor-objecto e que o número de cores discerníveis é um bom indicador desta diversidade, permitindo avaliar a influência de lentes coloridas ou de iluminantes com diferentes distribuições espectrais, em cenários de grande complexidade, para observadores normais ou deficientes da visão das cores. Com base na estimativa da variação da diversidade cromática em cenários complexos, é possível apresentar um índice – o CDI (“Chromatic Diversity Index”) que avalia as alterações cromáticas em tais cenários complexos provocadas por diferentes iluminantes, utilizando um reduzido número de amostras coloridas (1269 amostras de Munsell), para observadores normais e deficientes da visão das cores. Estes resultados permitem sugerir a utilização de determinados iluminantes para a observação de pinturas artísticas e cenários de interior com o objectivo de aumentar a diversidade cromática, para observadores normais e deficientes da visão das cores, resultados que poderão ser do interesse de museus, galerias de arte e utilizadores de ambientes específicos onde a discriminação cromática seja importante.The methods presently available to assess the quality of light sources have several limitations, in particular with the introduction of light sources based on LEDs. Some of the methods available (the Colour Rendering Index - CRI, the Gamut Area Index – GAI or the Colour Quality Scale - CQS) include in its computations parameters that extend the scope of the index beyond the colour reproduction capabilities as, for example, the colour gamut generated by the test illuminant. Although there are several indices they do not provide the assessment of the chromatic diversity on complex scenarios. Apart from this limitation they are only used with normal observers leaving aside the colour deficient observers. The purpose of this work was to estimate the chromatic diversity of complex scenes using data acquired using hyperspectral imaging and to use hyperspectral images of natural scenes, artistic paintings and indoor scenarios to estimate the influence on the chromatic diversity in complex scenes perceived by normal and colour deficient observers of illuminants with different spectral profiles. The aim is to present an index that will assist in the selection of illuminants for a particular task. It was found that the chromatic diversity of natural scenes is considerably inferior when compared to the expected result from the theoretical object colour volume and that the number of discernible colours is a good predictor of this diversity, enabling the estimate of the influence of coloured lens or illuminants with different spectral profiles on complex scenarios for normal and colour deficient observers. The Chromatic Diversity Index – CDI developed in the course of this work uses the computation of the chromatic diversity in complex scenarios to assess the chromatic changes induced by different illuminants by using a small set of coloured samples (the 1269 samples from the Munsell Colour Book), for normal and colour deficient observers. These results assist in the selection of an illuminant to view artistic paintings and indoor scenarios by proposing specific illuminants that will enhance the chromatic diversity of such scenes, not only for normal observers but also for colour deficient observers. The findings of this work could be of the interest of museums, art galleries or users of specific environments where chromatic discrimination is important.Fundação para a Ciência e a Tecnologia (FCT) - Bolsa de Doutoramento SFRH BD 35874 2007

Color diversity index : the effect of chromatic adaptation

Common descriptors of light quality fail to predict the chromatic diversity produced by the same illuminant in different contexts. The aim of this paper was to study the influence of the chromatic adaptation in the context of the development of the color diversity index, a new index capable of predicting illuminant-induced variations in several types of images. The spectral reflectance obtained from hyperspectral images of natural, indoor and artistic paintings, and the spectral reflectance of 1264 Munsell surfaces were converted into the CIELAB color space for each of the 55 CIE illuminants and 5 light sources tested. The influence of the CAT02 chromatic adaptation was estimated for each illuminant and for each scene. The CIELAB volume was estimated by the convex hull method and the number of discernible colors was estimated by segmenting the CIELAB color volume into unitary cubes and by counting the number of non-empty cubes. High correlation was found between the CIELAB volume occupied by the Munsell surfaces and the number of discernible colors and the CILEAB color volume of the colors in all images analyzed. The effects of the chromatic adaptation were marginal and did not change the overall result. These results indicate that the efficiency of the new illuminant chromatic diversity index is not influenced by chromatic adaptation

Assessment of compensation and simulation filters for colour vision deficiency

[Excerpt] Compensation filters may improve perception in humans with Red-Green colour vision deficiency (CVD) whilst simulation filters may mimic CVD in colour vision normals (CVN). A previous study (Lillo et al. 2014) showed that Variantor simulation filters mimic protanopia in a discrimination task when tested only at pseudoachromatic confusion axes. Studies (e.g. Gómez-Robledo et al. 2018) using EnChroma compensation filters (EnChroma, Berkeley, USA) have not found statistically significant improvements in colour vision. We aimed to assess effects of simulation (Variantor) and compensation (EnChroma) filters on perceptual performance in discrimination and colour naming tasks.- This work was supported by an Evelyn Trust Grant (to SJW) and HEFCE QR (Quality Related) Funds (to Anglia Vision Research) to support a Postdoctoral Research Fellow (LA) and visits (LA and JMML) to the laboratories of Anglia Vision Research, to facilitate completion of this project. The authors thank Ashley Gray (a research assistant supported by the QR fund), Emily Mailman and Laura Douds (who were undergraduate Optometry students) for their help with data collection

Lighting spectra for the maximum colorfulness

The advent of modern solid-state sources enabled almost any spectrum for lighting and a wide range of possibilities in color rendering. The quality of the lighting has been typically evaluated by the color rendering index which measures how much the colors of objects illuminated by the light under test look similar to those produced when the objects are illuminated by the daylight or a conventional incandescent light. On the other hand, how colorful or vivid the colors under the illumination are perceived is also an important quality to evaluate lighting. We investigated, computationally, the spectral profiles of the illumination that maximizes the theoretical limit of the perceivable object colors. A large number of metamers with various degree of smoothness were generated using the Schmitt’s elements method at chromaticity points on and around the Planckian locus ranging from 2,222 K to 20,000 K. The general color rendering index (CRI) and MacAdam volumes in CIELAB color space were calculated for each metamer. The metamers maximizing the CRI had smoother spectra than the metamers maximizing the MacAdam volume. These results show that maximum colorfulness in nature can only be obtained with spectrally non-smooth illuminatio

Effects of atopy and rhinitis on exhaled nitric oxide values - a systematic review

<p>Abstract</p> <p>Background</p> <p>Atopy and rhinitis are among the factors affecting exhaled nitric oxide (FeNO) values and may contribute to difficulties in the clinical interpretation of FeNO measurements. However, data assessing their effects on FeNO values had never been summarized. This review aims to evaluate the effect of atopy and rhinitis in FeNO values in otherwise healthy individuals.</p> <p>Methods</p> <p>A systematic review was performed in Pubmed, Scopus and ISI Web of Knowledge. A two-step selection process was completed, and from 2357 references 19 were included. The inclusion criteria were: participants without known diseases other than rhinitis; atopy assessement by SPT or Specific IgE; and FeNO measurements according to ATS/ERS recommendations.</p> <p>Results</p> <p>The 8 articles measuring FeNO in children showed higher values in both allergic rhinitis and atopic children when compared with healthy children. The 11 articles performed in adults observed higher FeNO in AR patients comparatively with either healthy or atopic individuals. However, adult healthy and atopic individuals had similar FeNO values.</p> <p>Conclusions</p> <p>FeNO values are higher in individuals with rhinitis and/or atopy without other health problems. These effects are small, seem to be independent and should be further studied using multivariate models. The effect of atopy was observed only in children. The combined effect of atopy and rhinitis produced higher FeNO values in adults. These results support that both atopy and rhinitis should be considered when interpreting or when defining FeNO reference values.</p

Robust colour constancy in red-green dichromats

Colour discrimination has been widely studied in red-green (R-G) dichromats but the extent to which their colour constancy is affected remains unclear. This work estimated the extent of colour constancy for four normal trichromatic observers and seven R-G dichromats when viewing natural scenes under simulated daylight illuminants. Hyperspectral imaging data from natural scenes were used to generate the stimuli on a calibrated CRT display. In experiment 1, observers viewed a reference scene illuminated by daylight with a correlated colour temperature (CCT) of 6700K; observers then viewed sequentially two versions of the same scene, one illuminated by either a higher or lower CCT (condition 1, pure CCT change with constant luminance) or a higher or lower average luminance (condition 2, pure luminance change with a constant CCT). The observers' task was to identify the version of the scene that looked different from the reference scene. Thresholds for detecting a pure CCT change or a pure luminance change were estimated, and it was found that those for R-G dichromats were marginally higher than for normal trichromats regarding CCT. In experiment 2, observers viewed sequentially a reference scene and a comparison scene with a CCT change or a luminance change above threshold for each observer. The observers' task was to identify whether or not the change was an intensity change. No significant differences were found between the responses of normal trichromats and dichromats. These data suggest robust colour constancy mechanisms along daylight locus in R-G dichromacy.This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the project PTDC/MHC-PCN/4731/2012 and by Ministerio de Ciencia y Competitividad in the framework of the project PSI2012-37778. LA was supported by Beca Santander JPI2014. The publication of this article was funded by the Anglia Ruskin Open Access Fund.info:eu-repo/semantics/publishedVersio

Discrimination of natural colors in anomalous trichromacy and the effects of EnChroma and Vino filters

It is still unclear how well anomalous trichromats discriminate natural colors and whether commercial spectral filters improve performance in these conditions. We show that anomalous trichromats have good color discrimination with colors drawn from natural environments. It is only about 14% poorer, on average, than normal trichromats in our sample of thirteen anomalous trichromats. No measurable effect of the filters on discrimination was found, even after 8 hours of continuous use. Computations of cone and post-receptoral signals show only a modest increase in medium-to-long-wavelength difference signals, which may explain the absent effect of the filters.Fundação para a Ciência e a Tecnologia (UIDB/FIS/04650/2020); Fundação para a Ciência e a Tecnologia/Fundo Social Europeu (2020.05785.BD

Development process and cognitive testing of CARATkids - Control of Allergic Rhinitis and Asthma Test for children

Funding Information: The authors would like to thank the children and caregivers and the physicians that participated in the study and the Sociedade Portuguesa de Alerglogia e Imunologia Clínica and Associação Portuguesa de Asmáticos e Alérgicos for the help and support the CARAT project. The consensus meetings had logistic and unrestricted financial support from MSD Portugal.Background: Allergic rhinitis and asthma (ARA) are chronic inflammatory diseases of the airways that often coexist in children. The only tool to assess the ARA control, the Control of Allergic Rhinitis and Asthma Test (CARAT) is to be used by adults. We aimed to develop the Pediatric version of Control of Allergic Rhinitis and Asthma Test (CARATkids) and to test its comprehensibility in children with 4 to 12 years of age.Methods: The questionnaire development included a literature review of pediatric questionnaires on asthma and/or rhinitis control and two consensus meetings of a multidisciplinary group. Cognitive testing was carried out in a cross-sectional qualitative study using cognitive interviews.Results: Four questionnaires to assess asthma and none to assess rhinitis control in children were identified. The multidisciplinary group produced a questionnaire version for children with 17 questions with illustrations and dichotomous (yes/no) response format. The version for caregivers had 4-points and dichotomous scales. Twenty-nine children, 4 to 12 years old, and their caregivers were interviewed. Only children over 6 years old could adequately answer the questionnaire. A few words/expressions were not fully understood by children of 6 to 8 years old. The drawings illustrating the questions were considered helpful by children and caregivers. Caregivers considered the questionnaire complete and clear and preferred dichotomous over the 4-points scales. The proportion of agreement between children and their caregivers was 61%. The words/expressions that were difficult to understand were amended.Conclusion: CARATkids, the first questionnaire to assess a child's asthma and rhinitis control was developed and its content validity was assured. Cognitive testing showed that CARATKids is well-understood by children 6 to 12 years old. The questionnaire's measurement properties can now be assessed in a validation study.publishersversionpublishe

Implicit knowledge of the colours of natural scenes matches real colours

Some studies suggest that there is a memory colour effect for familiar objects but whether this effect generalizes to natural scenes is unclear. Here we tested this hypothesis with an experiment where observers adjust the colour gamut of unknown natural scenes to produce realistic images. The stimuli were images of natural scenes unknown to the observers synthesized from hyperspectral imaging data. The images were rendered under D65 and could be manipulated to adjust the colour gamut in the CIELAB (a*, b*) by a multiplicative factor between 1.5 and 0.5. The images were presented on a calibrated CRT computer screen driven by a ViSaGe MKII. In the experiment the observers adjusted the gamut by actuating freely on a joy-pad. At the beginning of each trial each image was presented with its colour gamut compressed or expanded by a random factor. The task of the observers was to adjust the gamut such that the image appeared real. Data from five observers with normal colour vision shows that, on average, the gamut selected by observers was within 2% of the original one. These results suggest that observers have implicit unbiased knowledge of the colours of natural scenes.info:eu-repo/semantics/publishedVersio

Coloured filters can simulate colour deficiency in normal vision but cannot compensate for congenital colour vision deficiency

Red-green colour vision deficiency (CVD) affects ~ 4% of Caucasians. Notch filters exist to simulate CVD when worn by colour vision normal (CVN) observers (simulation tools), or to improve colour discrimination when worn by CVD observers (compensation tools). The current study assesses effects of simulation (Variantor) and compensation (EnChroma) filters on performance in a variety of tasks. Experiments were conducted on 20 CVN and 16 CVD participants under no-filter and filter conditions (5 CVN used Variantor; 15 CVN and 16 CVD used EnChroma). Participants were tested on Ishihara and Farnsworth-Munsell 100 hue tests, CVA-UMinho colour discrimination and colour naming tasks and a board-game colour-sorting task. Repeated-measures ANOVAs found Variantor filters to significantly worsen CVN performance, mimicking protanopia. Mixed-model and repeated-measures ANOVAs demonstrate that EnChroma filters do not significantly enhance performance in CVD observers. Key EnChroma results were replicated in 8 CVD children (Ishihara test) and a sub-sample of 6 CVD adults (CVA-UMinho colour discrimination and colour naming tasks) for a smaller stimulus size. Pattern similarity exists across hue for discrimination thresholds and naming errors. Variantor filters are effective at mimicking congenital colour vision defects in CVN observers for all tasks, however EnChroma filters do not significantly compensate for CVD in any