In 2004, an ISO committee found that insufficient data were available to make a decision on whether to recommend CIEDE2000 in place of DE_CMC. However, a provisional work item was initiated [1] to test independently the performance of the major color difference formulae specifically in the blue and near neutral regions. Accordingly, the objective of this work was to develop a new, comprehensive visual dataset around one blue color center, and to compare the performance of all the major formulae against the new dataset.A total of 5148 assessments using 66 textile sample pairs with small color differences (DE<5) were obtained. Each pair was visually assessed by 26 color normal observers in three separate sittings using a gray scale method. A third-degree polynomial equation was used to convert gray scale ratings to visual differences (DV). The performance of major formulae was evaluated based on a correlation coefficient (r) and the PF/3 measure at two lightness weights (K_L or l) of 1 and 2. Correlation coefficients of 0.91, 0.92 were obtained for CIEDE2000 at K_L of 1 and 2, which were the highest amongst the color difference equations examined although at K_L (or l)=2, CIEDE2000 and BFD performed comparably. Using the PF/3 metric the BFD equation gave the best results at both lightness scales (37.46, and 42.46 respectively), however, at K_L or l = 2, all major equations gave approximately the same performance.

This study investigates the distortion of visual colour harmony impression in case of different types of artificial changes among the perceptual attributes of test samples. A set of visual experiments were carried out to investigate the observer's colour harmony impression as a function of artificial distortions. The visual colour harmony impression of a colour combination appearing harmonious under a reference illuminant might decrease if the combination of samples is illuminated by different test light sources, especially RGB LED clusters. A new quantity, the so called Harmony Distortion Index (HDI) is defined to describe the harmony distortion property of light sources.

A model is presented to describe color effects based on interference on approximately periodic nano-structured surfaces. The model is verified qualitatively with optical color measurements on surface structured textile fibers, which show strong iridescent color effects. Good agreement can be found for the diffracted spectra as well as on images of diffraction patterns. Furthermore we show simulations and comparisons of the color appearance of bundles of parallel fibers. This model can be used as a base for simulating color effects in textile tissues, allowing a characterization and optimization in terms of fiber cross section, structure period and type for different lighting conditions.

The objective of this work is to predict the deviations between spectral measurements obtained by different devices for halftone prints. To describe the physics, the transport theory is considered, and to accurately solve the governing equations for arbitrary phase functions, a stochastic Monte Carlo method is employed. Recently, a stencil approach was developed, which allows to speed up such Monte Carlo algorithms significantly without compromising their accuracy. However, even with the stencil method the computational cost of well resolved simulations becomes exorbitant, if large halftone patches with huge numbers of individual dots are considered. To overcome this problem, a new multi-scale algorithm is devised. For large samples with statistically homogeneous dot patterns, it allows an additional increase of the efficiency without affecting the accuracy. In our studies we compare measurements of print patches captured with a hand-held eye one device and a microscopic spectrophotometer. Varying illumination and capturing geometries throughout different measuring devices pose a challenge to accurately predict the measurement differences with numerical models. These geometries were determined and implemented as boundary conditions of the simulated domains. Evaluations are presented that demonstrate reasonable agreement between the computed and the experimental data for ten halftone samples with ergodic, isotropic halftone patterns of different ink coverage.

Given a fixed set of viewing conditions, a colour appearance model provides a method for transforming tristimulus values to perceptual attributes correlates, and vice versa. Current colour appearance models, like CIECAM02 [1], have been developed assuming the CIE31 Standard Observer. However a general model must adequately describe the colorimetric behaviour of a large enough set of real observers. In this work we analyse the variability of the different parameters defined by CIECAM02 when different sets of colour-matching functions associated with real observers are considered. All our sets of colour-matching functions are for small-size fields (smaller than 4°). Our main goal is to evaluate the observer metamerism provided in CIECAM02 for a set of 13 real observers, when the reflectances of the 24 chips of the GretagMacbetch ColorChecker are illuminated under D65 and A illuminants.

Small displays are widely used, small enough to be carried around and are often viewed under extreme surround conditions. Under bright illuminating the mobile display experiences ‘veiling glare’ caused by the ambient lighting. A refined version of CIECAM02 called ‘Refined CIECAM02’ and original CIECAM02 were tested to predict visual results in terms of lightness, colourfulness, and brightness on a 2” mobile phone under four surround conditions (dark, dim, average, and bright). Other than the two versions of CIECAM02 using the original data, a correction to the models' predicted lightness J and a black correction to the original data were developed. Therefore six different versions were used to test and correct the veiling glare caused by the illumination. Overall, the refined CIECAM02 plus the J correction performed the best for predicting the lightness, brightness and colourfulness under all the viewing conditions especially for bright surround condition.

The effect on cone excitations of a change in illuminant on a scene may be predicted by von Kries scaling, but these predictions are not perfectly accurate. Here, a non-parametric method was used instead, but which preserved the principle of independence of activity in cone or cone-opponent mechanisms. Performance was evaluated over samples taken from 50 hyperspectral images of vegetated and non-vegetated natural scenes under large changes in daylight illuminant. Taking due account of differences in degrees of freedom, the non-parametric model gave significantly better predictions than von Kries scaling of cone or cone-opponent activity.

Professionals of the graphics arts industry require color reproduction accuracy and consistency across a large and open set of media. For color critical applications this typically means the use of a color measurement instrument. All of these tasks can be carried out today with off-line measurement devices and the corresponding software, but such systems are not easy to use, not integrated into the workflow, and expensive. Embedding color measurement capabilities inside a printer tries to solve most of these issues. This paper explains the specifications of the embedded spectrophotometer of the HP Z-series DesingJet Large Format Printers, the challenges that were found during its development and the improvement of the colorimetric performance of the printers that are using it.

This study investigates the effects of the size and the luminance value of the surround field on colour appearance under various viewing conditions. Ten phases of psychophysical experiments were conducted to obtain visual data assessed by a panel of 10-15 observers. The viewing conditions investigated include two sizes of surround field, three viewing distances, two luminance values of surround and three different sizes of stimuli. The accumulated visual data sets were used to test the CIE colour appearance model, CIECAM02, and the results showed that CIECAM02 gave a satisfactory prediction. Finally, the viewing parameters F, N_c and c in CIECAM02 were optimised to fit colour appearance results under different surround conditions. It was found a very small improvement.

This paper describes a method for the determination of the colour of inhomogeneous stains on textile using flatbed scanning (FBS) and image analysis (IA). The method can be used to assess the cleaning performance of laundry detergent products. Stains on textile were visualised using a standard flatbed scanner. A fully automatic procedure was developed using image analysis (IA) software. Different colorimetric calibration procedures were investigated. The method was tested on 24 different types of stain on cotton cloths and compared to the analysis using a spectrophotometer. FBS-IA can be used to analyse colour changes on stained textile. The method is sufficiently accurate and precise to screen different laundry detergent products. FBS-IA is fast, easy to use and cheap. Images can further be used to analyse the spatial distribution of inhomogeneous stains. The best agreement between FBS-IA and spectrophotometer was obtained using a 3 by 9 transformation matrix without linearization of the RGB response.