96 research outputs found

    Quantifying the colour appearance of displays.

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    EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    Visual Performance, and it\u27s Response to Intervention, in Subjects with Age-Related Macular Degeneration.

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    Abstract Objectives: 1. To explore visual performance status through a range of psychophysical methods beyond corrected distance visual acuity (CDVA), in subjects with age-related macular degeneration (AMD). 2. To investigate the effects on these visual performance parameters in subjects with neovascular age-related macular degeneration (nv-AMD) and in subjects with early AMD undergoing anti-VEGF (vascular endothelial growth factor) therapy and macular carotenoid supplementation, respectively. 3. To understand the role of a supplement containing meso-zeaxanthin (MZ; the third, and currently least explored, macular carotenoid) on the augmentation of macular pigment (MP), on visual performance and on disease progression (graded according to the AREDS [Age-Related Eye Disease Study] criteria), in subjects with early AMD. 4. To explore the impact of macular carotenoid supplementation on vision in subjects presenting with atypical macular pigment optical density (MPOD) spatial profiles at baseline. Outcomes: This study has shown that CDVA is not the most appropriate measure of visual function and does not reflect retinal morphology in cases of early AMD or in cases of nv-AMD. Retinotopic ocular sensitivity (ROS), however, appears to be a more reflective measure of disease severity, where it correlates well with AMD-severity grade (in cases of early AMD) and also with mean foveal thickness (MFT; in cases of nv-AMD). In eyes with nv-AMD undergoing monthly intravitreal ranibizumab injections, there have been demonstrable improvements in a range of parameters of visual function, namely, contrast sensitivity (CS), glare disability (GD), and ROS but no significant change in CDVA, despite a reduction in MFT. MP can be augmented, and CS enhanced, in subjects with early AMD who receive supplemental macular carotenoids. Subjects with low baseline central MPOD had the greatest increases in MPOD and the greatest improvements in CS, when compared with subjects with medium or high baseline MPOD, suggesting that the 4 optimisation of CS (and putatively visual performance in general) is somewhat dependent on central MP levels. The literature review has concluded that supplementation with the macular carotenoids offers the best means of fortifying the antioxidant defenses of the macula, thus putatively reducing the risk of AMD and/or its progression, and of optimising visual performance. Conclusions: The findings of this work suggest the incorporation of tests, complimentary to CDVA, such as CS, GD, and particularly ROS, when attempting to understand disease severity in cases of AMD. In terms of monitoring change over time, the results of this study do seem to indicate that measures of ROS may be particularly useful in monitoring subjects with nv-AMD, while measures of CS and GD may be more apt in monitoring change in subjects with early AMD. Macular carotenoid supplementation can enhance visual performance in subjects with early AMD

    Macular Pigment: Practical Implications for Optometric Practice in Preventative Health Care and Visual Performance Enhancement

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    The macula is a specialised part of the retina responsible for detailed central and colour vision. The carotenoids, lutein, zeaxanthin and meso-zeaxanthin are uniquely concentrated in the inner and central layers of the primate macula, where they are known as macular pigment (MP). It has been shown that MP is entirely of dietary origin and that lutein and zeaxanthin levels in serum, diet and retina correlate. Age-Related Macular Degeneration (AMD) is a disease of the macula and results in loss of central vision. MP, because of its optical filtration and antioxidant properties, may have an important role in the prevention or delay of AMD, and also in the enhancement and preservation of visual performance in healthy individuals

    Optimising Light Source Spectrum to Reduce the Energy Absorbed by Objects

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    Light is used to illuminate objects in the built environment. Humans can only observe light reflected from an object. Light absorbed by an object turns into heat and does not contribute to visibility. Since the spectral output of the new lighting technologies can be tuned, it is possible to imagine a lighting system that detects the colours of objects and emits customised light to minimise the absorbed energy. Previous optimisation studies investigated the use of narrowband LEDs to maximise the efficiency and colour quality of a light source. While these studies aimed to tune a white light source for general use, the lighting system proposed here minimises the energy consumed by lighting by detecting colours of objects and emitting customised light onto each coloured part of the object. This thesis investigates the feasibility of absorption-minimising light source spectra and their impact on the colour appearance of objects and energy consumption. Two computational studies were undertaken to form the theoretical basis of the absorption-minimising light source spectra. Computational simulations show that the theoretical single-peak spectra can lower the energy consumption up to around 38 % to 62 %, and double-peak test spectra can result in energy savings up to 71 %, without causing colour shifts. In these studies, standard reference illuminants, theoretical test spectra and coloured test samples were used. These studies are followed by the empirical evidence collected from two psychophysical experiments. Data from the experiments show that observers find the colour appearance of objects equally natural and attractive under spectrally optimised spectra and reference white light sources. An increased colour difference, to a certain extent, is found acceptable, which allows even higher energy savings. However, the translucent nature of some objects may negatively affect the results

    Color Appearance and Color Connotation for Unrelated Colors

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    Affective & Human Factors EngineeringThe purposes of this research are to identify relation between color perception and connotation of unrelated colors, and to develop mathematical models for color connotation. This research is significant in the sense that it provides fundamental data for color appearance and color connotation of unrelated colors on which there is a lack of research until now. To achieve these purposes, two psychophysical experiments were carried out. Experiment 1: Color perception for unrelated colors, to investigate color perception for unrelated color using the 50 color stimuli beamed through a square hole. Twenty-two observers have answered their perceived magnitudes of three color attributes based on the magnitude estimation. Experiment 2: Color connotation for unrelated colors, to examine color connotation for unrelated colors using the 50 color stimuli. Thirty-two observers have answered their connotation about each color stimulus using the 10 color connotation scales which consist of one aesthetic scale (i.e. ???like ??? Dislike???) and nine non-aesthetic scales (i.e. ???Warm ??? Cool,??? ???Heavy ??? Light,??? ???Modern ??? Classical,??? ???Clean ??? Dirty,??? ???Active ??? Passive,??? ???Hard ??? Soft,??? Tense ??? Relaxed,??? ???Fresh ??? Stale,??? and ???Masculine ??? feminine???). Semantic differential method was used for measurement of color connotation scales. The color connotation models having brightness, colorfulness and hue obtained by CAM97u and the revised CIECAM02 as input variables were developed to quantify inter-relation between the color attributes and color connotation space, and further effects of the color attributes on color connotation were visually analyzed based on conventional bubble charts. The major findings from the experiments are summarized as follows: In experiment 1: Color perception for unrelated colors, the experimental results shows that the three perceptual attributes of unrelated colors such as brightness, colorfulness and hue can be estimated by the colorimetric properties of color stimuli (i.e. luminance, excitation purity and CIE 1976 hue-angle). It is found that the estimate values of the color attributes are positively proportional to perceived magnitudes of the color attributes. The performance comparison is made of proposed estimation model with CAM97u and revised CIECAM02. The revised CIECAM02 gives the best satisfactory estimations of brightness, colorfulness and hue under photopic vision. In experiment 2: Color connotation for unrelated colors, the experimental results shows that color connotation of unrelated colors has a three-dimensional space, and the three axes are ???Color solidity,??? ???Color heat,??? and ???Color purity.??? ???Color solidity??? is associated with ???Hard-Soft,??? ???Heavy-Light,??? ???Tense-Relaxed,??? and ???Active-Passive.??? ???Color heat??? is correlated with ???Warm-Cool??? and ???Feminine-Masculine???, and ???Color purity??? has relevance to ???Clean-Dirty??? and ???Fresh-Stale.??? In short, color connotation for unrelated colors is a function of the three color appearance attributes. All the color connotation scales are correlated with the color attributes. Four color connotation scales, ???Warm-Cool,??? ???Heavy-Light,??? ???Active-Passive??? and ???Hard-Soft???, were modeled. The scale ???Warm-Cool??? is associated with hue angle and colorfulness, while significant relation between ???warm-Cool??? and brightness is not found. The other scales are connected with the color difference between the test color and neutral color of which brightness are varied with the color connotation scales. This implies that ???Heavy-Light,??? ???Active-Passive??? and ???Hard-Soft??? have relevance to colorfulness. Furthermore, the three-dimensional color connotation space for unrelated colors is associated with the color attributes. The significant correlations between the axes of the color connotation space and color attributes are as follows: ???Color solidity??? with colorfulness, ???Color heat??? with both hue angle and colorfulness, ???Color purity??? with brightness. There is room for further improvement and development in this research. (1) The data sets obtained by this research need to examine repeatability, (2) relationships of color connotations between unrelated colors and related colors is required to be analyzed, and (3) the results of this research should expend into applications in association with emotional lighting.ope

    LAMP SPECTRUM AND RELATIVE SPATIAL BRIGHTNESS AT PHOTOPIC LIGHT LEVELS

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    This thesis proposes that the spectral power distribution (SPD) of lighting can be modified to enhance spatial brightness. Energy saving is then possible by using SPD that allows illuminance to be reduced whilst maintaining the same level of spatial brightness. The Akashi and Boyce study demonstrates an energy saving of 33% by using lamps of higher correlated colour temperature but it is widely known that this is not a good metric for predicting spatial brightness. The aim of this study was to identify a metric for predicting spatial brightness. The first approach followed the method of Cowan and Ware: use the results of past experiments to test potential metrics. 65 studies of spatial brightness and SPD were found. Initially, these lead to different conclusions as to whether SPD affects spatial brightness. The reasons for this are that they used different methodologies and hence review of method was used to screen the credible data from within these 65 studies: only 19 of them were considered to be credible. This thesis focussed on the category rating procedure. The review of methods included an experiment comparing rating scales with different response ranges and a meta-analysis comparing results gained when either brightness or visual clarity were the objective of the experiment. Two potential metrics for spatial brightness are the scotopic to photopic (S/P) luminance ratio and the area of the colour gamut (GA). Results from the credible studies were used to test these models: while both models suggest a reasonable prediction, it was found that they were not independent for this set of data and it was therefore not possible to discriminate between them. Hence an experiment was carried out to directly test these metrics. The experiment employed full field sequential evaluation of stimulus pairs, with matching and discrimination procedures. Three SPDs were compared, these chosen to isolate the S/P and GA effects. Following Berman et al, one pair had identical chromaticity but different S/P ratios: a second pair had identical S/P ratio but different gamut area; the third pair had different S/P and gamut area. The two procedures led to similar results: null condition trials confirmed that doubt about interval bias in the Berman et al data was unwarranted. It was found that lighting of higher S/P or higher GA enhance spatial brightness: it was also found that their effects appear to be additive. When the final remodelling was done by adding the data points from the new experiment to the data set, the models of the difference of S/P ratio and the log ratio of GA had the best fits with spatial brightness. Their correlations were equally plausible with mean illuminance ratio of the data set. This thesis demonstrates that SPD affects spatial brightness, allowing lower illuminances to be used when using lighting of higher S/P ratio and gamut area

    Proceedings experiencing light 2009 : international conference on the effects of light on welbeing

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    Investigating the visual tasks of pedestrians and how one of these tasks, obstacle detection, is influenced by lighting

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    Current guidelines for pedestrian road lighting are not based on empirical evidence. One approach to providing suitable evidence is to examine the effect of lighting on the visual tasks of pedestrians. This first requires an understanding of what these visual tasks are. An eye-tracking study was carried out in which pedestrians walked a real, outdoor route during the day and after-dark. A novel dual-task method was used to identify the critical visual tasks of the pedestrians. Reaction times to a concurrent audio response task were used to indicate instances when attention may have been diverted towards something significant in the visual environment. Analysis of the eye-tracking videos at these critical times found that the path and other people were the two most significant items looked at. Observation of the path is important for detection and avoidance of obstacles and trip hazards. Good road lighting should therefore facilitate obstacle detection. An obstacle detection experiment was therefore carried out examining the effect of illuminance and Scotopic/Photopic (S/P) ratio on obstacle detection. The experiment improved the realism and ecological validity of previous research by introducing a dynamic fixation target, realistic apparatus scales and real walking (on a treadmill) whilst carrying out an obstacle detection task. Results showed that obstacle detection only improved with illuminance increases up to 2.0 lux. A higher S/P ratio (2.0) provided better detection performance than a low S/P ratio (1.2), but only at the lowest illuminance used of 0.2 lux. The data is used to discuss optimal design criteria for pedestrian road lighting based on obstacle detection. However, other purposes of road lighting, such as creating a feeling of reassurance and enabling accurate interpersonal judgements to be carried out, should also be considered when designing pedestrian road lighting
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