Evaluation and improvement of the workflow of digital imaging of fine art reproduction in museums

Fine arts refer to a broad spectrum of art formats, ie~painting, calligraphy, photography, architecture, and so forth. Fine art reproductions are to create surrogates of the original artwork that are able to faithfully deliver the aesthetics and feelings of the original. Traditionally, reproductions of fine art are made in the form of catalogs, postcards or books by museums, libraries, archives, and so on (hereafter called museums for simplicity). With the widespread adoption of digital archiving in museums, more and more artwork is reproduced to be viewed on a display. For example, artwork collections are made available through museum websites and Google Art Project for art lovers to view on their own displays. In the thesis, we study the fine art reproduction of paintings in the form of soft copy viewed on displays by answering four questions: (1) what is the impact of the viewing condition and original on image quality evaluation? (2) can image quality be improved by avoiding visual editing in current workflows of fine art reproduction? (3) can lightweight spectral imaging be used for fine art reproduction? and (4) what is the performance of spectral reproductions compared with reproductions by current workflows? We started with evaluating the perceived image quality of fine art reproduction created by representative museums in the United States under controlled and uncontrolled environments with and without the presence of the original artwork. The experimental results suggest that the image quality is highly correlated with the color accuracy of the reproduction only when the original is present and the reproduction is evaluated on a characterized display. We then examined the workflows to create these reproductions, and found that current workflows rely heavily on visual editing and retouching (global and local color adjustments on the digital reproduction) to improve the color accuracy of the reproduction. Visual editing and retouching can be both time-consuming and subjective in nature (depending on experts\u27 own experience and understanding of the artwork) lowering the efficiency of artwork digitization considerably. We therefore propose to improve the workflow of fine art reproduction by (1) automating the process of visual editing and retouching in current workflows based on RGB acquisition systems and by (2) recovering the spectral reflectance of the painting with off-the-shelf equipment under commonly available lighting conditions. Finally, we studied the perceived image quality of reproductions created by current three-channel (RGB) workflows with those by spectral imaging and those based on an exemplar-based method

Modeling age-related ocular media changes using the Farnsworth Munsell (FM) 100-Hue Test

Introduction: Evaluation of chromatic discrimination can help diagnose and monitor diseases and disorders of the visual system; however, normal age-related changes can make diagnosing colour discrimination losses challenging. This problem holds especially for the Farnsworth Munsell 100 Hue test (FM100 Hue). Identifying specific contributions of areas of the visual system that influence the FM100 Hue performance could aid in establishing standardized interpretation of test results and help understand the mechanisms contributing to the age-related changes. Purpose: This study aimed to examine the theoretical changes in the FM100 Hue scores produced by age-related changes in the ocular media transmittances. These changes were examined with, and without, a von Kries type chromatic adaptation to determine the role of this adaptation process on age-related changes in hue discrimination. Materials and methods: We calculated the CIECAM02 chromaticity coordinates of the FM100 Hue caps for 32-year-old and 74-year-old as ideal observers. These values were then used to predict the ordering of the FM100 Hue caps. The chromaticity coordinates were based on the spectral distribution of Illuminant D65, the spectral reflectances of the individual caps, and the CIE 1931 2o standard observer colour matching functions. In calculating the values of the old observers, we modified the spectral distributions of the D65 light sources using Pokorny et al.’s and van de Kraats and van Norren’s model of media transmittance to account for the relative change in transmittance from a 32-year-old observer to a 74-year-old observer. We also accounted for the decrease in retinal illumination in the older observers due to pupil miosis and the decrease in ocular media luminous transmittance. The order of the caps was based on the minimum colour differences (ΔE) between nearby caps. The mean and standard deviation of the colour differences for each tray was calculated. The mean colour difference was also determined for the caps in the blue-yellow (BY) and red-green (RG) quadrants. Results: With complete and partial adaptation, the Total Error Score (TES) increased from 8 for the younger observer to12 for both older observer models of media transmittance. The ordering for the caps along the blue-yellow axis was unchanged from the younger observer. Without adaptation, the error score for the older observer model increased further. The increase was primarily for caps along the red-green axis for van de Kraats and van Norren’s model, whereas the increase for Pokorny et al.’s model was along both the red-green and blue-yellow axis. The mean colour differences across trays for the young observer model were marginally larger than the old observer models for complete and partial adaptation. When the caps were grouped in the RG and BY quadrants, the mean differences for the older observers were still lower than the young observer. Differences between the BY and RG error scores were also larger for the older observers. Without adaptation, the mean colour differences for the older observer models were uniformly lower than with complete or partial adaptation. Conclusion: The predicted effect of age-related changes in media transmittances on the ordering of the FM100 Hue test showed an increase in the TES, as expected. The increase, however, was primarily due to an increase in the RG partial error score, which disagrees with the psychophysical data showing a larger increase in the BY error score. This discrepancy suggests that age-related neural changes are also occurring, which is consistent with conclusions from other psychophysical studies. The two different models for age-related media changes produced similar changes in the FM100 error scores. Chromatic adaptation may compensate for age-related media changes

TESTING COLOR APPEARANCE MODELS IN COMPLEX SCENE

The sensation of sight is our primary mechanism to perceive the world around us. However it is not yet perfectly clear how the human visual system works. The images of the world are formed on the retina, captured by sensors and converted in signals sent to the brain. Here the signals are processed and somehow interpreted, thus we are able to see. A lot of information, hypothesis, hints come from a field of the optical (or visual) illusions. These illusions have led many scientists and researchers to ask themselves why we are not able to interpret in a correct way some particular scenes. The word \u201cinterpret\u201d underlines the fact that the brain, and not only the eye, is involved in the process of vision. If our sight worked as a measurement tool, similar to a spectrophotometer, we would not perceive, for example, the simultaneous contrast phenomenon, in which a grey patch placed on a black background appears lighter than an identical coloured patch on a white background. So, why do we perceive the patches as different, while the light that reaches the eyes is the same? In the same way we would not be able to distinguish a white paper seen in a room lit with a red light from a red paper seen under a white light, however humans can do this. These phenomena are called colour appearance phenomena. Simulating the appearance is the objective of a range of computational models called colour appearance models. In this dissertation themes about colour appearance models are addressed. Specific experiments, performed by human observers, aim to evaluate and measure the appearance. Different algorithms are tested in order to compare the results of the computational model with the human sensations about colours. From these data, a new printing pipeline is developed, able to simulate the appearance of advertising billboard in different context