Expanding Dimensionality in Cinema Color: Impacting Observer Metamerism through Multiprimary Display

Television and cinema display are both trending towards greater ranges and saturation of reproduced colors made possible by near-monochromatic RGB illumination technologies. Through current broadcast and digital cinema standards work, system designs employing laser light sources, narrow-band LED, quantum dots and others are being actively endorsed in promotion of Wide Color Gamut (WCG). Despite artistic benefits brought to creative content producers, spectrally selective excitations of naturally different human color response functions exacerbate variability of observer experience. An exaggerated variation in color-sensing is explicitly counter to the exhaustive controls and calibrations employed in modern motion picture pipelines. Further, singular standard observer summaries of human color vision such as found in the CIE’s 1931 and 1964 color matching functions and used extensively in motion picture color management are deficient in recognizing expected human vision variability. Many researchers have confirmed the magnitude of observer metamerism in color matching in both uniform colors and imagery but few have shown explicit color management with an aim of minimized difference in observer perception variability. This research shows that not only can observer metamerism influences be quantitatively predicted and confirmed psychophysically but that intentionally engineered multiprimary displays employing more than three primaries can offer increased color gamut with drastically improved consistency of experience. To this end, a seven-channel prototype display has been constructed based on observer metamerism models and color difference indices derived from the latest color vision demographic research. This display has been further proven in forced-choice paired comparison tests to deliver superior color matching to reference stimuli versus both contemporary standard RGB cinema projection and recently ratified standard laser projection across a large population of color-normal observers

EVALUATION OF DISTRIBUTION HISTOGRAMS FOR INCREMENT OF CHROMATICITY COORDINATES IN DISPLAY TECHNOLOGIES

We consider evaluation problem of chromaticity coordinates increment for an image displayed by indicating means (liquid crystal panels and etc.). Display device profile set by the weight matrix for components of primary colors serves as basic data for quantitative calculation. Research results have the form of mathematical expressions allowing calculation of increment values of chromaticity coordinates of the image displayed on indicating means and histograms of increment distribution

Modeling Perceptual Trade-offs for Designing HDR Displays

Display technology has evolved in pursuit of perceptual pleasure by providing realism and visual impact. The endeavor of the evolution has brought HDR displays to the market. HDR displays, which have become the mainstream display technology recently, are considered not only the present but also the future of displays because of their daunting technical goals: A peak luminance of 10,000 cd/m^2 and near-monochromatic primaries. However, both positive and negative prospects in terms of perceptual aspects for future HDR displays coexist. On the positive side, it is expected that HDR displays will provide better image quality and more vivid color. On the negative side, apart from technical barriers such as production cost and power consumption, HDR displays will induce side effects, for example, observer metamerism, which refers to the phenomenon that color matches for one observer result in color mismatches for other observers. This particular side effect could be a severe issue in HDR displays as their narrow-band primaries likely worsen the color mismatches. Hence, critical to the success of future HDR displays is dealing properly with the perceptual trade-offs. In other words, future HDR display designers need to select physical specifications that maximize perceptual benefits while minimizing adverse effects. This dissertation aims at exploring both potentially positive and negative aspects of future HDR displays, using various perceptual assessments. In particular, the dissertation focuses on two physical factors of a display device: peak luminance and chromaticity color gamut, and the effects of the two factors on related human perception: image quality, observer metamerism, and colorfulness. The ultimate goal of this dissertation is to address the related human perception aroused by the physical factors and propose models to help design future HDR displays. In order to achieve the goal, the dissertation first addresses the image quality trade-off relationship between peak luminance and chromaticity color gamut. A psychophysical experiment was used to develop models to predict equivalent image quality under the trade-off between peak luminance and chromaticity gamut as a function of the perceptual attributes lightness and chroma. Second, a novel approach based on a computational evaluation to investigate potential observer metamerism in HDR displays was explored. This research shows how observer metamerism in HDR displays varies with varying peak luminance and chromaticity color gamut. This research aims at developing a straightforward model to predict observer metamerism in HDR displays based on the computational evaluation. Third, a psychophysical experiment to derive a colorfulness scale for very saturated colors is carried out. This experiment focuses on understanding how the sensitivity of the human visual system responds to highly-saturated colors that extend beyond the stimuli studied in previous research. The colorfulness scale would help both advanced lighting system and display system designers. Fourth, the dissertation suggests an evaluation tool devised based on the observer metamerism and colorfulness scale works that can be utilized to determine the physical specification of HDR displays, maximizing perceptually positive effects while minimizing perceptually negative effects at the same time

Navigating the roadblocks to spectral color reproduction: data-efficient multi-channel imaging and spectral color management

Commercialization of spectral imaging for color reproduction will require the identification and traversal of roadblocks to its success. Among the drawbacks associated with spectral reproduction is a tremendous increase in data capture bandwidth and processing throughput. Methods are proposed for attenuating these increases with data-efficient methods based on adaptive multi-channel visible-spectrum capture and with low-dimensional approaches to spectral color management. First, concepts of adaptive spectral capture are explored. Current spectral imaging approaches require tens of camera channels although previous research has shown that five to nine channels can be sufficient for scenes limited to pre-characterized spectra. New camera systems are proposed and evaluated that incorporate adaptive features reducing capture demands to a similar few channels with the advantage that a priori information about expected scenes is not needed at the time of system design. Second, proposals are made to address problems arising from the significant increase in dimensionality within the image processing stage of a spectral image workflow. An Interim Connection Space (ICS) is proposed as a reduced dimensionality bottleneck in the processing workflow allowing support of spectral color management. In combination these investigations into data-efficient approaches improve two critical points in the spectral reproduction workflow: capture and processing. The progress reported here should help the color reproduction community appreciate that the route to data-efficient multi-channel visible spectrum imaging is passable and can be considered for many imaging modalities