Digital Color Imaging

This paper surveys current technology and research in the area of digital color imaging. In order to establish the background and lay down terminology, fundamental concepts of color perception and measurement are first presented us-ing vector-space notation and terminology. Present-day color recording and reproduction systems are reviewed along with the common mathematical models used for representing these devices. Algorithms for processing color images for display and communication are surveyed, and a forecast of research trends is attempted. An extensive bibliography is provided

A Computational analysis of observer metamerism in cross-media color matching

Standard color-matching functions are designed to represent the mean color-matching response of the population of human observers with normal color vision. When using these functions, two questions arise. Are they an accurate representation of the population? And what is the uncertainty in color-match predictions? To address these questions in the dual context of human visual performance and cross-media reproduction, a color-matching experiment was undertaken in which twenty observers made matches between seven different colors presented in reflective and transmissive color reproduction media and a CRT display viewed through an optical apparatus that produced a simple split field stimulus. In addition, a single observer repeated the experiment 20 times to quantify intra-observer variability. The results are used to evaluate the accuracy of three sets of color-matching functions, to quantify the magnitude of observer variability, and to compare intra- and inter-observer variability in color matching. These results are compared with current CIE recommendations on observer metamerism. The magnitude of observer variability in this experiment also provides a quantitative estimate of the limit of cross-media color reproduction accuracy that need not be exceeded

Quantifying mixed adaptation in cross-media color reproduction

This paper describes an investigation undertaken to address the goal set by the CIE Technical committee TC8- 04: To investigate the state of adaptation of the visual system when comparing soft-copy images on self-luminous displays and hard copy images viewed under various ambient lighting conditions. A set of psychophysical experiments have been conducted for the determination of corresponding colors between printed stimuli under CIE Illuminant D50 simulators and CRT displayed stimuli with a D93 white point. The experiments were completed with 15 observers and 6 different viewing conditions. Analysis was completed to quantify any systematic effects of viewing configuration and to identify the extent to which existing adaptation and appearance models can predict the results. After examining a number of adaptation transforms, preliminary results showed how a simple von Kries type adaptation transform provided the best predictions for all conditions while subsequent iterations of the von Kries transform using simple ratios between the adapting and ambient illuminants improved upon these results. The results also indicated how the CIECAM97s model, given certain conditions, could provide results equal to or better than the von Kries model

Color reproduction of CRT-displayed images as projected transparencies

This thesis evaluated the color appearance predictions of four digital color transforms (Hunt, RLAB, CIELAB, and von Kries) between CRT original images, viewed in a lighted room, and projected slides, viewed in the dark. Calibrated projection of these images required resolution of several complex issues. Upon projection, the slide colors changed. A rapid color shift (on the order of 75 seconds) was followed by a slower, steady degradation which also had to be minimized for accurate image presentation. Therefore, a model of the film behavior was based upon dye absorptivities and color measurements of slides as they were projected. The psychophysical experiments included a comparison between preference choices and memory matching to the CRT original. Two CRT white points were evaluated: D93 and D65. The preference choices were, in fact, distinct from the selected matches. RLAB produced statistically superior matches over any other model for both white points. Model performance was image dependent. Occasionally, CIELAB or von Kries images were equivalent to RLAB. However, CIELAB and von Kries predictions ranged widely in their performance. Hunt\u27s image predictions consistently gave the worst results. Interestingly, RLAB was also elected as the most acceptable choice: judged \u27acceptable\u27 in more than 2/3 of all cases, with a maximum approval of 89%

Digital Image Access & Retrieval

The 33th Annual Clinic on Library Applications of Data Processing, held at the University of Illinois at Urbana-Champaign in March of 1996, addressed the theme of "Digital Image Access & Retrieval." The papers from this conference cover a wide range of topics concerning digital imaging technology for visual resource collections. Papers covered three general areas: (1) systems, planning, and implementation; (2) automatic and semi-automatic indexing; and (3) preservation with the bulk of the conference focusing on indexing and retrieval.published or submitted for publicatio

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

Influence of viewing conditions on cross-media color matching

We investigated observer metamerism under a variety of viewing conditions, in a set of color-matching experiments using displays and printed color samples under specific light sources. A selection was made of light sources with different illuminances, spectral power distributions, and correlated color temperatures, as well as displays with different sets of primaries. A panel of 157 observers with normal color vision and ages between 20 and 59 years old performed 5465 visual color matches around 9 different color centers. The results from the simulated and real experiments were quite different. Specifically, the mean color difference from the mean changed with experimental viewing conditions, ranging from 0.73 to 1.64 CIELAB units (average 0.99 CIELAB units) in simulated experiments, and from 3.12 to 4.03 CIELAB units (average 3.55 CIELAB units) in real experiments. In real experiments, observers’ variability reduced for light sources with high illuminance and high correlated color temperature. Spectral power distributions affected observer metamerism, but the role played by the primaries of the two displays employed was unclear.National Natural Science Foundation of China (NNSFC), 61675029. Ministry of Economy and Competitiveness of the Government of Spain, co-financed by the European Regional Development Fund (ERDF) of the European Union, research project FIS2016-80983-P

Quantifying mixed adaptation in cross-media color reproduction

An investigation has been undertaken to address the goal set by the CEE Technical committee TC8-04: To investigate the state of adaptation of the visual system when comparing soft-copy images on self-luminous displays and hard copy images viewed under various ambient lighting conditions A set of psychophysical experiments have been conducted for the determination of corresponding colors between printed stimuli under CIE Illuminant D50 simulators and CRT displayed stimuli with a D93 white point. The experiments were completed with 15 observers and 6 different viewing conditions. Analysis was completed to quantify any systematic effects of viewing configuration and to identify the extent to which existing adaptation and appearance models can predict the results. After examining a number of adaptation transforms, preliminary results showed how a simple von Kries type adaptation transform provided the best predictions for all conditions while subsequent iterations of the von Kries transform using simple ratios between the adapting and ambient illuminants improved upon these results. The results also indicated how the CIECAM97s model, given certain conditions, could provide results equal to or better than the von Kries model