Compensation of the eye's aberrations with adaptive optics allows high resolution images and identification of individual cones in the living human eye. Such images, combined with psychophysical measures in the same eyes, reveal the effect of the trichromatic cone mosaic on color and spatial vision. Perhaps the most striking conclusion from this work is how little impact the topography of the mosaic has on vision, illustrating the brain's cleverness in concealing variations in cone topography from our visual experience. Application of adaptive optics imaging of the cone mosaics of color blind eyes in conjunction molecular genetics has revealed a new cause for color blindness. Finally, adaptive optics can also be used to probe single cones in the human eye with tiny flashes of light. This produces a striking variation of color experience from flash to flash that calls for a revision of prevailing models of human color processing.

In this study we propose a new image enhancement technique named Dynamic Band Imaging (DBI) which changes its parameters in time. DBI is the technology based on multi-spectral estimation to enhance the endoscopic color images in order to distinguish the slight color difference more clearly. From some results of fundamental analysis by subjective evaluations, DBI represents the effectiveness for image enhancement in comparison with the typical still image evaluation. Furthermore we developed the user interface to determine many parameters easily and then some practical appropriate parameters for endoscopic diagnosis are obtained. DBI is found as the effective method to enhance medical images.

The color reproduction accuracy of a multispectral video system was visually evaluated by expert dermatologists to investigate the feasibility of the system in telemedicine applications. The erythema produced by a skin prick test was used as a substitution of real skin lesion, and the dermatologists performed a color matching experiment, in which the color chips were compared with the reproduced images and the real skins. As a result, the mutisperctral video system, consisting of 6-band HDTV camera, 6-primary display and spectrum-based color reproduction, decreased the perceptual color difference between the reproduced image and the real object, as compared with a conventional 3-band HDTV system. It was also shown that the oversights of skin lesions could be reduced in 6-band video reproduction. Through the experiments including multispectral video transmission between the remote hospitals in addition to above skin color matching, dermatologists rated that the natural color reproduction realized by multispectral video is almost satisfactory for the diagnosis of skin disorders.

The performance of the black ink in ink-jet printing is of great importance to both ink-jet manufacturers and ink suppliers. Many black ink formulations contain several dyes or pigments and have a noticeable hue. The industry requires a suitable method for assessing the relative perceptual blackness of black inks. In this study, a set of black printed samples have been visually ranked in terms of perceptual blackness. Various candidate blackness indices have been evaluated and the best has been shown to be able to make pair-wise blackness comparisons with greater accuracy than the average observer.

High image quality on the small display of mobile phones is becoming highly desirable as the availability of functions for playing computer games, watching still and moving images. An experiment was carried out to accumulate colour appearance data on a 2″ mobile display using the magnitude estimation method. It was divided into nine phases according to three surrounds (dark, dim and average) and three backgrounds (light-grey, black, and white). The visual data are expressed in terms of lightness, colourfulness and hue. The visual results from different phases were compared to reveal different colour appearance effects. The results were also used to test and refine the CIE colour appearance model, CIECAM02 [1]. Two revised versions were made as a new mobile colour appearance model. There were large improvements from the new versions, especially for the colourfulness results.

Eleven observers made colour matches between LCD and CRT monitors and paint samples in viewing conditions similar to those of soft-proofing. The matches were used to evaluate the practical significance of observer metamerism and of failures of colorimetric additivity in cross-media colour matching.The individual variations in matches are of magnitudes that are expected to have practical consequences in graphic arts applications; they can not be explained by observer metamerism and thus can not be modelled by the Standard Deviate Observer. At the other hand, these variations are modelled well by the CIEDE2000 colour difference formula.Failures of colorimetric additivity lead to systematic disagreements in cross-media matches made by individual observers and predicted by the CIE 1964 Standard Colorimetric Observer. The discrepancies are consistent with all the reports on the subject, but have never been confirmed to exist in practical colorimetry. A chromatic adaptation modelling framework can be used to compensate for the failures in practical applications.We conclude that additivity failure is a significant contributor to the uncertainty of colour matching, and needs to be accounted for in industrial colour management systems. The practical implications of individual variability which is not the result of observer metamerism remains unclear.

A human observer has never stood on the surface of Mars, yet color images from Mars have been produced. The twin Mars Exploration Rovers (MERs) have been on the surface of Mars for over two (earth) years and have taken many 1000's of images. The MER Pancam can acquire calibrated multispectral images that can be processed to produce colorimetric “true-color” images of Mars. While these images are primarily intended to allow science – in particular geology – to be done, they can also be used to display the Martian scenes in roughly representative color. The Pancam images can be further processed using color appearance models to produce “true color appearance” images that should display the color appearance to humans. CIECAM02 is applied to the colorimetric true-color images to Martian scenes to simulate the true color appearance.

Due to increasing printing accuracies and the possibility of printing several droplets at the same pixel location, there is a renewed interest in dot-on-dot printing models. In the present contribution, we improve a dot-on-dot spectral prediction model relying on the Yule-Nielsen modified Spectral Neugebauer model by taking into account ink spreading in all ink superposition conditions. Since ink spreading is different when ink dots are printed alone, printed in superposition with one ink or printed in superposition with two inks, we create for each superposition condition an ink spreading function mapping nominal to effective dot surface coverages. When predicting the reflection spectrum of a dot-on-dot halftone patch, its known nominal surface coverage values are converted into effective coverage values by weighting the contributions from different ink spreading functions according to the corresponding ratio of colorant surface coverages. We analyze the colorimetric prediction improvement brought by our ink spreading model for dot-on-dot thermal transfer prints and for ink-jet prints. Accounting for ink spreading according to different ink superposition conditions considerably improves the prediction accuracy. In the case of ink jet prints at 120 lpi, the mean ΔE94 difference between predictions and measurements is reduced from 4.54 to 1.55 (accuracy improvement factor: 3). Due to the slight misregistration between the ink layers, spectral predictions accounting for ink spreading in the case of dot-on-dot screens are less accurate than corresponding predictions for classical mutually rotated screens.

Color inverse tables, although seemingly accurate, introduce color errors and artifacts near the gamut boundary of a device. These artifacts are due to a combination of gamut mapping and interpolation: Gamut mapping breaks the correspondence between connection and device space vertices, and interpolation subsequently fails. An algorithm has been designed for more accurate inversions at the gamut boundary. It is based on the extrapolation of vertices instead of gamut mapping and interpolation. Results on different printers and media types show a significant improvement in color accuracy near the gamut boundary compared to standard inversion techniques.

Several techniques for the computation of gamut boundaries have been presented in the past. In this paper we take an in-depth look at some of the gamut boundary descriptors used when performing today's gamut mapping algorithms. We present a method for evaluating the mismatch introduced when using a descriptor to approximate the boundary of a device gamut. First, a visually verified reference gamut boundary is created by triangulating the gamut surface using a device profile or a device characterization model. The different gamut boundary descriptor techniques are then used to construct gamut boundaries based on several sets of simulated measurement data from the device. These boundaries are then compared against the reference gamut by utilizing a novel voxel based approach. Preliminary results from experiments using several gamut boundary descriptors are presented, and the performance of the different algorithms is discussed.