Chromatic Adaptation Model Research Articles

Weighted Geometric Mean (WGM) method: A new chromatic adaptation model.

The human visual system has undergone evolutionary changes to develop sophisticated mechanisms that enable stable color perception under varying illumination. These mechanisms are known as chromatic adaptation, a fundamental aspect of color vision. Chromatic adaptation can be divided into two categories: sensory adaptation, which involves automatic adjustments in the visual system, such as retinal gain control, in response to changes in the stimulus, and cognitive adaptation, which depends on the observer's knowledge of the scene and context. The geometric mean has been suggested to be the fundamental mathematical relationship that governs peripheral sensory adaptation. This paper proposes the WGM model, an advanced chromatic adaptation model based on a weighted geometric mean approach that can anticipate incomplete adaptation as it moves along the Planckian or Daylight locus. Compared with two other chromatic adaptation models (CAT16 and vK20), the WGM model is tested with different corresponding color data sets and found to be a significantly improvement while also predicting degree of adaptation (sensory and cognitive adaptation) in a physiologically plausible manner.

Weighted Geometric Mean (WGM) Method: A New Chromatic Adaptation Model

The geometric mean has been suggested to be the fundamental mathematical relationship that governs peripheral sensory adaptation. This paper proposes the WGM model, an advanced chromatic adaptation model based on a weighted geometric mean approach that can anticipate incomplete adaptation as it moves along the Planckian or Daylight locus. Compared with two other chromatic adaptation models (CAT16 and vK20), the WGM model shows more accuracy in predicting previous visual data.

Reversibility of Corresponding Colors in Sensory Chromatic Adaptation

In colorimetry and color appearance modeling it is assumed that chromatic adaptation is reversible. Recent experimental results suggest that this might not be the case and that bidirectional models of chromatic adaptation might be needed. This paper describes a series of experiments designed to collect very-high precision corresponding colors data for sensory chromatic adaptation to test the hypothesis that chromatic adaptation is reversible for individual observers. The results indicate that there are small, but statistically significant, differences in corresponding colors due to changes in the previous state of adaptation. However the effect sizes are small and the number of repeated observations required to detect these differences is very large. Thus it is concluded that these differences are, while interesting, not problematic for practical colorimetry. In addition the application of the vk20 chromatic adaptation model for predicting such effects is further explored and its 15000K reference adaptation state is validated.

Study of display white point based on mixed chromatic adaptation.

In this study, the settings of the display white points were investigated, which presented the color appearance matched with a neutral surface as observed in the state of mixed chromatic adaptation. A psychophysical experiment was conducted under 20 illumination and viewing conditions via successive binocular color matching. It is discovered that the metameric light sources have generally equivalent effects on the observers' adaptation states and the resulting white points. The correlated color temperature (CCT) of the illumination and the adapting luminance, both with a significant influence on the mixed chromatic adaptation, exhibit a positive and a negative relation to the white point CCT, respectively. The immersive illumination affects the white point through the adaptation ratio and the baseline illuminant. Finally, the experimental results were verified to be predictable with an amended mixed chromatic adaptation model, which produced a mean chromaticity error of only 0.0027 units of CIE 1976 u'v'.

61‐1: Invited Paper: Enhanced Viewing Experience Considering Chromatic Adaptation

We describe the advanced chromatic adaptation model and framework employed in Apple's True Tone Displays. Combining the theoretical model and empirical user study results, True Tone Display is able to deliver a more color consistent viewing experience.

Limits of Color Constancy: Comparison of the signatures of chromatic adaptation and spatial comparisons

Color Constancy has two hypothetical mechanisms: Chromatic Adaptation and Spatial Comparisons. These mechanisms have different fundamental properties. Adaptation models work with small individual scene segments. They combine radiance measurements of individual segments with the modeler’s selected parameters that scale the receptor’s cone quanta catches. Alternatively, spatial models use the radiance map of the entire field of view to calculate appearances of all image segments simultaneously. They achieve independence from spectral shifts in illumination by making spatial comparisons within each L, M, S color channel. These spatial comparisons respond to color crosstalk caused by the overlap of spectral sensitivities of cone visual pigments. L, M, and S cones respond to every visible wavelength. Crosstalk causes the spatial comparisons of cone responses to vary with changes in spectral illumination. Color Constancy works best in spatially uniform, and variable spectral illumination. Measurements of Color Constancy show systematic departures from perfect constancy. These limits of Color Constancy are predicted by spatial comparisons with cone Crosstalk. These limits do not correlate with Chromatic Adaptation models. This paper describes cone Crosstalk, and reviews a series of measurements of the limits of Color Constancy in variable spectral, spatial and real-life illuminations.

Multi-purpose bi-local CAT-based guidance filter

In this paper, we propose a new guidance filter, based on color perception through a chromatic adaptation model. Our method consists of a patch-wise linear transformation, which transfers details from a guidance image to an input image. The amount of transferred details is controlled by a novel chromatic adaptation transform (CAT), called bi-local CAT, embedded in our method. The bi-local CAT contributes to the detail recovery from the guidance image as well as to the preservation of the input reflections and shadows. Our bi-local CAT-based guidance filter is applied in various image processing domains, such as image denoising, image deblurring, texture transfer, detail enhancement, skin beautification, etc.

Color constancy from invariant wavelength ratios: An algorithm to simplify the chromatic adaptation model

AbstractIn a recent article on color constancy, the chromatic adaptation model was of a novel type comprising three components separately calculated—hue, chromaticness, and lightness. The constant hue component was a simple calculation of predicted wavelength but the other two components were less direct. This article provides an algorithm to simplify the model's calculation. Calculation is far simpler and more intuitive than conventional models using complex 3 × 3 matrix transforms with their various and contentious adaptation primaries and potential disadvantages (e.g., in brightness and color gamut). The model is shown to be at least as accurate as six other (conventional) models and does not require high math skill. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 468–476, 2016

Prediction of Incomplete Chromatic Adaptation Under Illuminant A from Images

The authors propose a method of image rendering to predict the incomplete chromatic-adaptation effect for paintings. A simple model of incomplete chromatic adaptation is developed to predict the appearance of the paintings under the illumination of an incandescent light source and to produce the full color image on a display device. The authors extend the von Kries framework to incomplete chromatic adaptation. An index parameter representing the degree of incomplete chromatic adaptation is defined based on the color temperature of the black-body radiators. First, the optimum value of the index parameter is determined by visual experiments on memory matching using real paintings and color patches, so that the color image produced on the display is matched to the original appearance of objects in a real scene. This approach is shown to have better performance in comparison with the traditional CIECAM02. Next, an algorithm is presented to estimate the index parameter of the incomplete adaptation index based on the image data of colorimetric rendering for a target painting. It is found that the index parameter can be estimated using only three features extracted from the color image. The color images rendered with the estimated parameter are used to predict the incomplete chromatic-adaptation effect for the original painting under the incandescent light source. The feasibility of the proposed method is confirmed based on a series of experiments using a variety of paintings. © 2014 Society for Imaging Science and Technology. [DOI:10.2352/J.ImagingSci.Technol.2014.58.3.030403]

Corresponding color datasets and a chromatic adaptation model based on the OSA-UCS system.

Today chromatic adaptation transforms (CATs) are reconsidered, since their mathematical inconsistency has been shown in Color Res. Appl.38, 188 (2013) and by the CIE technical committee TC 8-11: CIECAM02 Mathematics. In 2004-2005 the author proposed an adaptation transform based on the uniform color scale system of the Optical Society of America (OSA-UCS) [J. Opt. Soc. Am. A21, 677 (2004); Color Res. Appl. 30, 31 (2005)] that transforms the cone-activation stimuli into adapted stimuli. The present work considers all the 37 available corresponding color (CC) datasets selected by CIE and (1) shows that the adapted stimuli obtained from CC data are defined up to an unknown transformation, and an unambiguous definition of the adapted stimuli requires additional hypotheses or suitable experimental data (as it is in the OSA-UCS system); (2) produces a CAT, represented by a linear transformation between CCs, associated with any CC dataset, whose high quality measured in ΔE units discards the possibility of nonlinear transformations; (3) analyzes these color-conversion matrices in a heuristic way with a reference adaptation that is approximately that of the OSA-UCS adapted colors for the D65 illuminant and particularly shows accordance with the Hunt effect and the Bezold-Brücke hue shift; (4) proposes the measurements of CC stimuli with a reference adaptation equal to that of the visual situation of the OSA-UCS system for defining adapted colors for any considered illumination adaptation and therefore for defining a general CAT formula.

Number of discernible object colors is a conundrum

Widely varying estimates of the number of discernible object colors have been made by using various methods over the past 100 years. To clarify the source of the discrepancies in the previous, inconsistent estimates, the number of discernible object colors is estimated over a wide range of color temperatures and illuminance levels using several chromatic adaptation models, color spaces, and color difference limens. Efficient and accurate models are used to compute optimal-color solids and count the number of discernible colors. A comprehensive simulation reveals limitations in the ability of current color appearance models to estimate the number of discernible colors even if the color solid is smaller than the optimal-color solid. The estimates depend on the color appearance model, color space, and color difference limen used. The fundamental problem lies in the von Kries-type chromatic adaptation transforms, which have an unknown effect on the ranking of the number of discernible colors at different color temperatures.

Chromatic Adaptation Transforms to Accommodate Printed Color Matching in Paper with Optical Brightening Agents (OBA)

The color reproduction is based on visual perception. The psychophysics experiments present the light source; illuminants and view background affect the results of color matching. Paper is a typical substrate for printed color matching and effects printed color greatly. Now almost all of print papers contain optical brightening agents, which changes significantly the color appearance of printed color and makes color shifting of printed color matching. This paper used CAT02 chromatic adaptation models to transform the measurements of printed color in paper with and without OBA, compared the effect of printed color matching between before and after transforming with display, present the method using chromatic adaptation transforms to improve the accurate of printed color matching.

Color constancy from invariant wavelength ratios. III: Chromatic adaptation theory, model and tests

AbstractA theory of chromatic adaptation is derived from Parts I and II, and presented in terms of relative wavelength, purity, and radiant power, leading directly to a predictive model of corresponding hue, chroma, and lightness. Considering that even simple animals have effective color vision and color constancy, the aim was to develop a simple model of complete adaptation. The model is tested against well‐known data sets for corresponding colors in illuminants D65, D50, and A, and for small and large visual fields, and performs comparably to CIECAM02. Constant hue is predicted from Part I's mechanism of color constancy from invariant wavelength ratios, where constant hues shift wavelength linearly with reciprocal illuminant color temperature. Constant chroma is predicted from constant colorimetric purity. Constant lightness is predicted from chromatic adaptation of spectral sensitivity represented by power ratios of complementary colors (rather than cone responses which lack spectral sharpening). This model is the first of its type and is not formatted for ease of computation. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2010

High fidelity color reproduction of plasma displays under ambient lighting

This paper proposes a method of color reproduction that considers the observer's viewing conditions and characteristics of a PDP display. In general, ambient lighting requires compensation to provide the same visual perception when the temporal and spatial conditions change. In a conventional method, the image contrast and saturation are enhanced by controlling the voltage gain in each channel to consider the phenomenon of human adaptation. Yet, this method encounters difficulties in reproducing the perceived stimulus under a variety of viewing conditions. Accordingly, this study characterizes a PDP display based on the white point when considering the average picture level of the PDP display as the maximum luminance value of a PDP display varies according to the average picture level. Next, to consider the viewing conditions, information on the ambient lighting is obtained using a sensor. The flare, the reflected ambient lighting, is also eliminated on the surface of the PDP display. Finally, the color values are calculated using a modified chromatic adaptation model. In experiments, images reproduced using the proposed method were visually superior to those reproduced using a conventional method.

A Chromatic Adaptation Model for Mixed Adaptation Conditions

When we watch television or computer monitor under a certain viewing condition, we partially adapt to the display and partially to the ambient light. As an illumination level and chromaticity change, the eye's subjective white point changes between the display's white point and the ambient light's white point. In this paper, we propose a model that could predict the white point under a mixed adaptation condition including display and illuminant. Finally we verify this model by experimental results.

Spectral adaptation

AbstractChromatic adaptation refers to the ability of the human visual system to adjust to the color of the illumination, or other prevailing stimuli, such that perceived object colors vary far less with changes in illumination than would be expected from simple radiometry or colorimetry. Models of chromatic adaptation are generally formulated as extensions of the von Kries hypothesis of some sort of independent gain control mechanisms operating on the three types of cone, or similar signals. This article introduces a new way to model the phenomenon with no requirement for the first stage chromatic processing. This model is referred to as a spectral adaptation model since it acts upon spectra rather than chromatic signals such as tristimulus values. The spectral adaptation model was compared with other models of adaptation both computationally and through limited psychophysical data. It is shown to have reasonable and flexible performance and could be of practical value in applications such as spectral image reproduction. A limiting case of the spectral model, a model of perfect color constancy, is also described and compared with traditional colorimetric chromatic adaptation models. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 100 – 112, 2007

Visual and infrared dual-band false color image fusion method motivated by Land’s experiment

A new false color image fusion method is proposed on the basis of Land's experiment on color constancy of human vision, through idealized hypothesis of the red filter and green filter, through equienergy distribution hypothesis of the light source, and by relating the infrared and visual images to the black-and-white transparencies obtained through the red and green filters of Land's experiment, respectively. The normalization of each color channel conforms with the von Kries chromatic adaptation model and the maximum red-green-blue method, which has been popularly adopted in some video systems and color theories to estimate the illumination color and which, to a certain extent, agrees with the color constancy of human vision. The method has been proven effective after it was compared with Toet et al.'s fusion method. Its colorfulness is enhanced by the strategy of assigning the difference between the source images to the blue channel, which is used in Toet et al.'s algorithm to underscore the characteristic components of the individual images. The additional opponent processing neurodynamic equation of the center-surround receptive field can improve the output contrast significantly and is believed to be more suitable for revealing details by human observers. Some perceptual evaluation results are also given at the end.

Chromatic Adaptation Model Using the Relationship between the Cone Responses under Change in Illuminants

In this paper, a chromatic adaptation model (CAM) based on the dependence on LMS cone responses of the human visual system (HVS) is proposed for TV and PC monitors under a variety of viewing conditions. We derived the proposed CAM based on Breneman's corresponding color data. The results of the experiments were carried out to assess the proposed model performance in terms of color fidelity by comparing complex images on a LCD monitor. We confirmed that the proposed model performed better to predict corresponding colors under various viewing conditions. Therefore, the reproduced colors, which are viewed in real surround viewing conditions, are perceived the same as original object colors, when the proposed CAM was applied to color display devices such as CRT, LCD, and PDP.

Spectral Based Color Correction Technique Compatible with Standard RGB System

A spectral turn method is presented as a spectral based color correction method compatible with the standard RGB system by applying the idea of a multi-spectral method. The multi-spectral based color reproduction technique has been proposed for providing independent color of device and viewing conditions. However, it is difficult to replace the RGB devices with high cost multi-spectral devices since the latter have advanced only to the laboratory level. In the proposed method, the standard RGB values are converted into spectral information, then returned to RGB values for different viewing conditions. This process provides more accurate reproduction than the conventional forward process of the color reproduction. An experiment of psychophysical color matching was performed to evaluate the technique. The mixed chromatic adaptation model was applied to the method in the experiment, and the results showed the effectiveness of the proposed method.

Evaluation of color matching performances for SPEM and other models

AbstractWe performed subjective experiments to evaluate color matching performance of the Spectral Properties Estimation Model (SPEM) and six other models (von Kries, CIELAB, LLAB, RLAB, Nayatani, and CIECAM97s) between two CRT monitors whose whites were quite different. Moreover, we evaluated color matching of these models between a CRT monitor and a printed image set in a dark room. The SPEM we developed is a new chromatic adaptation model based on hypothetical spectral properties estimation. This article describes the subjective experiments and the results obtained. The SPEM produced good color matching performance in the experiments. The detailed algorithm of the SPEM is given in the Appendix. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 445–453, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10197