136 research outputs found
Perception of Color Break-Up
Hintergrund. Ein farbverfälschender Bildfehler namens Color Break-Up (CBU) wurde untersucht. Störende CBU-Effekte treten auf, wenn Augenbewegungen (z.B. Folgebewegungen oder Sakkaden) während der Content-Wiedergabe über sogenannte Field-Sequential Color (FSC) Displays oder Projektoren ausgeführt werden. Die Ursache für das Auftreten des CBU-Effektes ist die sequenzielle Anzeige der Primärfarben über das FSC-System. Methoden. Ein kombiniertes Design aus empirischer Forschung und theoretischer Modellierung wurde angewendet. Mittels empirischer Studien wurde der Einfluss von hardware-, content- und betrachterbasierten Faktoren auf die CBU-Wahrnehmung der Stichprobe untersucht. Hierzu wurden zunächst Sehleistung (u. a. Farbsehen), Kurzzeitzustand (u. a. Aufmerksamkeit) und Persönlichkeitsmerkmale (u. a. Technikaffinität) der Stichprobe erfasst. Anschließend wurden die Teilnehmenden gebeten, die wahrgenommene CBU-Intensität verschiedener Videosequenzen zu bewerten. Die Sequenzen wurden mit einem FSC-Projektor wiedergegeben. Das verwendete Setup ermöglichte die Untersuchung folgender Variablen: die Größe (1.0 bis 6.0°) und Leuchtdichte (10.0 bis 157.0 cd/m2) des CBU-provozierenden Contents, das Augenbewegungsmuster des Teilnehmenden (Geschwindigkeit der Folgebewegung: 18.0 bis 54.0 °/s; Amplitude der Sakkade: 3.6 bis 28.2°), die Position der Netzhautstimulation (0.0 bis 50.0°) und die Bildrate des Projektors (30.0 bis 420.0 Hz). Korrelationen zwischen den unabhängigen Variablen und der subjektiven CBU-Wahrnehmung wurden getestet. Das ergänzend entwickelte Modell prognostiziert die CBU-Wahrnehmung eines Betrachters auf theoretische Weise. Das Modell rekonstruiert die Intensitäts- und Farbeigenschaften von CBU-Effekten zunächst grafisch. Anschließend wird die visuelle CBU-Rekonstruktion zu repräsentativen Modellindizes komprimiert, um das modellierte Szenario mit einem handhabbaren Satz von Metriken zu quantifizieren. Die Modellergebnisse wurden abschließend mit den empirischen Daten verglichen. Ergebnisse. Die hohe interindividuelle CBU-Variabilität innerhalb der Stichprobe lässt sich nicht durch die Sehleistung, den Kurzzeitzustand oder die Persönlichkeitsmerkmale eines Teilnehmenden erklären. Eindeutig verstärkende Bedingungen der CBU-Wahrnehmung sind: (1) eine foveale Position des CBU-Stimulus, (2) eine reduzierte Stimulusgröße während Sakkaden, (3) eine hohe Bewegungsgeschwindigkeit des Auges und (4) eine niedrige Bildrate des Projektors (Korrelation durch Exponentialfunktion beschreibbar, r2 > .93). Die Leuchtdichte des Stimulus wirkt sich nur geringfügig auf die CBU-Wahrnehmung aus. Generell hilft das Modell, die grundlegenden Prozesse der CBU-Genese zu verstehen, den Einfluss von CBU-Determinanten zu untersuchen und ein Klassifizierungsschema für verschiedene CBU-Varianten zu erstellen. Das Modell prognostiziert die empirischen Daten innerhalb der angegebenen Toleranzbereiche. Schlussfolgerungen. Die Studienergebnisse ermöglichen die Festlegung von Bildraten und Eigenschaften des CBU-provozierenden Content (Größe und Position), die das Überschreiten vordefinierter, störender CBU-Grenzwerte vermeiden. Die abgeleiteten Hardwareanforderungen und Content-Empfehlungen ermöglichen ein praxisnahes und evidenzbasiertes CBU-Management. Für die Vorhersage von CBU kann die Modellgenauigkeit weiter verbessert werden, indem Merkmale der menschlichen Wahrnehmung berücksichtigt werden, z.B. die exzentrizitätsabhängige Netzhautempfindlichkeit oder Änderungen der visuellen Wahrnehmung bei unterschiedlichen Arten von Augenbewegungen. Zur Modellierung dieser Merkmale können teilnehmerbezogene Daten der empirischen Forschung herangezogen werden.Background. A color-distorting artifact called Color Break-Up (CBU) has been investigated. Disturbing CBU effects occur when eye movements (e.g., pursuits or saccades) are performed during the presentation of content on Field-Sequential Color (FSC) display or projection systems where the primary colors are displayed sequentially rather than simultaneously. Methods. A mixed design of empirical research and theoretical modeling was used to address the main research questions. Conducted studies evaluated the impact of hardware-based, content-based, and viewer-based factors on the sample’s CBU perception. In a first step, visual performance parameters (e.g., color vision), short-term state (e.g., attention level), and long-term personality traits (e.g., affinity to technology) of the sample were recorded. Participants were then asked to rate the perceived CBU intensity for different video sequences presented by a FSC-based projector. The applied setup allowed the size of the CBU-provoking content (1.0 to 6.0°), its luminance level (10.0 to 157.0 cd/m2), the participant’s eye movement pattern (pursuits: 18.0 to 54.0 deg/s; saccadic amplitudes: 3.6 to 28.2°), the position of retinal stimulation (0.0 to 50.0°), and the projector’s frame rate (30.0 to 420.0 Hz) to be varied. Correlations between independent variables and subjective CBU perception were tested. In contrast, the developed model predicts a viewer’s CBU perception on an objective basis. The model graphically reconstructs the intensity and color characteristics of CBU effects. The visual CBU reconstruction is then compressed into representative model indices to quantify the modeled scenario with a manageable set of metrics. Finally, the model output was compared to the empirical data. Results. High interindividual CBU variability within the sample cannot be explained by a participant’s visual performance, short-term state or long-term personality traits. Conditions that distinctly elevate the participant’s CBU perception are (1) a foveal stimulus position on the retina, (2) a small-sized stimulus during saccades, (3) a high eye movement velocity, and (4) a low frame rate of the projector (correlation expressed by exponential function, r2 > .93). The stimulus luminance, however, only slightly affects CBU perception. In general, the model helps to understand the fundamental processes of CBU genesis, to investigate the impact of CBU determinants, and to establish a classification scheme for different CBU variants. The model adequately predicts the empirical data within the specified tolerance ranges. Conclusions. The study results allow the determination of frame rates and content characteristics (size and position) that avoid exceeding predefined annoyance thresholds for CBU perception. The derived hardware requirements and content recommendations enable practical and evidence-based CBU management. For CBU prediction, model accuracy can be further improved by considering features of human perception, e.g., eccentricity-dependent retinal sensitivity or changes in visual perception with different types of eye movements. Participant-based data from the empirical research can be used to model these features
Evaluation of the color image and video processing chain and visual quality management for consumer systems
With the advent of novel digital display technologies, color processing is increasingly becoming a key aspect in consumer video applications. Today’s state-of-the-art displays require sophisticated color and image reproduction techniques in order to achieve larger screen size, higher luminance and higher resolution than ever before. However, from color science perspective, there are clearly opportunities for improvement in the color reproduction capabilities of various emerging and conventional display technologies. This research seeks to identify potential areas for improvement in color processing in a video processing chain. As part of this research, various processes involved in a typical video processing chain in consumer video applications were reviewed. Several published color and contrast enhancement algorithms were evaluated, and a novel algorithm was developed to enhance color and contrast in images and videos in an effective and coordinated manner. Further, a psychophysical technique was developed and implemented for performing visual evaluation of color image and consumer video quality. Based on the performance analysis and visual experiments involving various algorithms, guidelines were proposed for the development of an effective color and contrast enhancement method for images and video applications. It is hoped that the knowledge gained from this research will help build a better understanding of color processing and color quality management methods in consumer video
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Perception-Aware Optimisation Methodologies for Quantum Dot Based Displays and Lighting
Human colour vision acuity is limited. This presents opportunities to leverage these perceptual limits to achieve engineering optimisations for devices and systems that interact with the human vision system. This dissertation presents the results of few investigations we carried out into quantifying these limits and several optimisation methodologies that we devised. The first step in this process is to quantify the acuity of human colour vision. We obtained a large corpus of colour matching data from a mobile video game called Specimen. We examine what questions about human vision this dataset allows us to answer and explore global statistics about colour vision based on this data on 41,000 players from 175 countries. We show that we can use the information in this dataset to infer potential candidate functions for the spectral sensitivities of each person in the dataset. The human eye acts like a many to one function; quantifiably different spectra can look like the same colour. This is referred to as metamerism. From a device perspective, different spectra consume different amounts of energy to generate. We show that we can use these two properties to elicit the same colour sensation using less energy. In the colour samples we evaluated, we show that we can achieve up to 10 times less power consumption while achieving a colour match. Given that one cannot change the emission spectrum of a display after fabrication, we propose the use of a multi-primary colour display to achieve this. We present two indices for quantifying the metameric capacity of such a display and its ability to save energy. The emission spectrum of a quantum dot (QD) based device is very narrow. Previous work in the literature suggested that narrow bandwidth spectra can lead to observer metameric breakdown; different observers disagreeing on the perceived ‘colour’ of a spectrum. We show that this might not be the case, using modern colour science tools, and show how metameric breakdown in a display could be minimised by carefully choosing the primary emission wavelengths. The limited colour acuity of human vision implies that people cannot notice small differences in colour. This fact has been used to create approximate colour transformation algorithms that subtly change colours in images such that they consume less energy when displayed on an emissive pixel display without causing unacceptable visual artefacts. We conducted a user study to gather information about the effect of one such colour transform called Crayon. We present a method for effectively picking the optimal transform parameters for Crayon, based on the user study results. The method presented calculates these parameters based on the properties of the image being transformed such that the power saving can be maximised while minimising the loss of image quality. The user study results show that we can achieve up to 50% power saving with a majority of the study participants reporting a negligible degradation in image quality in the transformed images. We additionally investigate a hypothesis that was presented stating that images with large amounts of highly luminous pixels cause increased power consumption in OLED displays due to localised display heating. We show that this hypothesis is wrong. We also investigate if sub-pixel rendering in Pentile displays can be used to reduce display power consumption by intentionally turning off random sub-pixels. However, we present a negative result showing that even single-pixel artefacts are observable on the test platform and thus, this cannot be used to improve display power efficiency. The narrow-band optical emissions of QD based devices mixed with their ability to be fabricated through solution processing can be used to mix multiple QDs together to build devices that generate arbitrary spectral shapes. We show how to use this property in an numerical optimisation based design framework to create lighting devices with a high colour rendering index (CRI). We evaluate the effects of different cost functions and initialisation strategies, and show that, we are able to design devices with a CRI > 96 using only four different QD primaries. We use a charge-transport based simulator to asses the electric properties of the designed devices. We also showcase initial work done on a modular software interface and a material library we developed for this simulator.EPSRC DTP studentship award RG84040:EP/N509620/
Impact of Illumination Correlated Color Temperature, Background Lightness, and Painting Color Content on Color Appearance and Appreciation of Paintings
© 2019, © 2019 Illuminating Engineering Society. Lighting design for art exhibitions has a significant impact on the enjoyment and understanding of the displayed artworks. In particular, the selection of the light sources and the design of the museum space affect the visitors' visual perceptions of the artworks and their color appearance. This project investigated some of the potential factors—the correlated color temperature (CCT) of the illumination, the overall color content of the painting and the lightness of its background—affecting a painting's color appearance and appreciation in a museum setting. The study involved a survey conducted in the laboratory with both naïve observers and lighting experts. The CCT of the lighting was found to be the main factor affecting the painting's appearance and the observers' overall preference for the lighting arrangements, whereas the overall hue content of the painting and the background lightness had a minor influence. Furthermore, it has been found that the perceived brightness increases along with the CCT. ispartof: LEUKOS vol:16 issue:1 pages:25-44 status: publishe
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