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

Chromatic noise perception in digital photography

A model was built to predict chromatic noise perception in digital photography. The model includes the orthogonal opponent color space Y C1C2, and sets of optimized contrast sensitivity functions. Past research on opponent colors, contrast sensitivity functions at threshold and suprathreshold matching has been reviewed. Some historical opponent color spaces have been investigated in terms of transformation and application. Three psychophysical experiments were performed to build the model. Through the equi-luminance plane experiment three equi-luminance planes corresponding to three luminance levels were determined. Method of adjustment was applied for subjects to adjust chromatic noise image until it is least perceptible. Based on results from the first experiment, the orthogonal opponent color space Y C1C2 was developed. The Y C1C2 space shows optimal performance compared with OPP space, with the respect of separating luminance information from chromatic channels and vice versa. The threshold experiment measured contrast threshold for the three cardinal axes and the two diagonal axes of the new opponent color space with three frequency bands and three luminance levels. The QUEST procedure was applied for observers to choose which one of the two side-by-side-displayed stimuli has noise. The supra-threshold experiment was to measure contrast sensitivity above threshold. Method of adjustment was used for observers to adjust the noise contrast of the test stimuli to match the contrast of the parallel displayed achromatic anchor stimuli, which had three times threshold contrast. Sets of optimized CSFs were obtained by empirical modeling on experiment data from the threshold and supra-threshold experiments. The five-parameter band-pass CSF was fitted to model achromatic noise. As to chromatic noise, the six-parameter low-pass CSF was optimized to model chromatic noise. The fact that threshold CSFs and suprathreshold CSFs have similar shape suggests one set of CSFs may be applicable for both cases

Quantifying pigment cover to assess variation in animal colouration

The study of animal colouration addresses fundamental and applied aspects relevant to a wide range of fields, including behavioural ecology, environmental adaptation and visual ecology. Although a variety of methods are available to measure animal colours, only few focus on chromatophores (specialized cells containing pigments) and pigment migration. Here, we illustrate a freely available and user friendly method to quantify pigment cover (PiC) with high precision and low effort using digital images, where the foreground (i.e., pigments in chromatophores) can be detected and separated from the background. Images of the brown shrimp, Crangon crangon were used to compare PiC with the traditional Chromatophore Index (CI). Results indicate that PiC outcompetes CI for pigment detection and transparency measures in terms of speed, accuracy and precision. The proposed methodology provides researchers with a useful tool to answer essential physiological, behavioural and evolutionary questions on animal colouration in a wide range of species

Spectral imaging of human portraits and image quality

This dissertation addresses the problem of capturing spectral images for human portraits and evaluating image quality of spectral images. A new spectral imaging approach is proposed in this dissertation for spectral images of human portraits. Thorough statistical analysis is performed for spectral reflectances from various races and different face parts. A spectral imaging system has been designed and calibrated for human portraits. The calibrated imaging system has the ability to represent not only the facial skin but also the spectra of lips, eyes and hair from various races as well. The generated spectral images can be applied to color-imaging system design and analysis. To evaluate the image quality of spectral imaging systems, a visual psychophysical image quality experiment has been performed in this dissertation. The spectral images were simulated based on real spectral imaging system. Meaningful image quality results have been obtained for spectral images generated from different spectral imaging systems. To bridge the gap between the physical measures and subjective visual perceptions of image quality, four image distortion factors were defined. Image quality metrics were obtained and evaluated based statistical analysis and multiple analysis. The image quality metrics have high correlation with subjective assessment for image quality. The image quality contribution of the distortion factors were evaluated. As an extension of the work other researchers in MCSL have initiated, this dissertation research will, working with other researchers in MCSL, put effort to build a publicly accessible database of spectral images, Lippmann2000