Comparison of the munsell,NCS, DIN,and coloroid colour order systems using the OSA-UCS model

An earlier article described the use of a colour notation conversion program to measure the accuracy of the NCS, DIN and OSA-UCS color atlases. This article describes the application of the same program to compare the perceptual scaling of the Munsell, NCS, DIN, and Coloroid systems with that of the OSA-UCS system. Five OSA-UCS cleavage planes were selected which represent a varied but systematic sampling of OSA-UCS colour space. The samples contained on these planes were converted onto the colour spaces of the Munsell, NCS, DIN and Coloroid systems. The converted points have been displayed graphically for ease of comparison.     

Determination of colorcurve colour atlas sample deviation and comparison with NCS,DIN and OSA-UCS atlas sample deviation

This article presents an evaluation of the deviation of the Colorcurve atlas samples from their designated aim points. Sample deviations are evaluated in terms of hue, chroma, and lightness. In addition, the deviation of the Colorcurve samples from their respective aim points are graphically represented for eighteen lightness levels, Comparison is provided with NCS, DIN, and OSA-UCS atlas sample deviation.     

The british building colour standards: Conversion to the notations of munsell,NCS, din,coloroid, colorcurve,and OSA-UCS

This article provides Munsell (aim and actual), NCS (aim and actual), DIN (aim and actual), Coloroid (aim), Colorcurve (aim and actual), and OSA-UCS (aim and actual) notations for the 237 colour samples that comprise BS5252. These notations were obtained from recent spectrophotometric measurement of the standard, using a new version of the colour notation conversion program initially developed at the University of Teesside. © 1995 John Wiley & Sons. Inc.     

Interrelation of the Swiss Colour Atlas (SCA-2541) and the Munsell Color Order System

The CIE tristimulus values of measured Swiss Colour Atlas samples were converted to Munsell notations using a colour notation conversion program. A selected subset of SCA-2541 sample points was chosen: the samples on the fully populated regularly spaced hues 6, 12, 18, 24, 30, 36, 42, 48, 54, and 60. The resulting Munsell notations were plotted onto Munsell Value-Chroma and Hue-Chroma planes and analysed for regularity of spacing and hue distribution around the achromatic axis. An earlier article has detailed the interrelation between the Natural Color System (NCS) and the Munsell Color Order System using similarly constructed charts. Comparison is made with the sample spacing of the NCS and SCA-2541 points when mapped into Munsell colour space, to determine similarities and differences between these two geometrically similar systems; both are double cones forming equilateral triangular constant hue planes. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 111–120, 1997     

Why colour order systems?

In this introductory lecture to the AIC Forsius Symposium on Colour Order Systems, the author reviews color order systems from a historical point of view as samplings of the World of Colour, seeking with each example to find an answer to the question posed in the title.     

Perceptual factors affecting colour order systems

The perceptual colour attributes relevant for ordering unrelated, related, luminous, and nonluminous colours are different insome respects. Colour order systems for related nonluminous colours have been the most fully developed, but different systems depend on different types of experimental data, such as equalization of small perceptual differences, colour scaling, and some relationships to properties of the stimuli. The resulting systems have both similarities and differences, which are worthy of careful study. Chromatic adaptation is an important factor affecting and appearances of samples of colour order systems viewed in illuminants of various colours, and requires further study.     

The basic concepts and attributes of colour order systems

One of the first—if not the first—colour order system described in the literature is that of the Swedish scientist Forsius in his book Physica, published in 1611, and the Symposium at which this article was presented was organised to provide a forum for discussion of the philosophy and principles underlying the various colour order systems that have been developed since that time. Two main types of colour order system can be identified, depending on the subjective variables of colour appearance on which they are based. These variables are discussed in this article with particular reference to the Munsell System and the Natural Colour System, the chief representatives of the two types of system, together with some comments on colour naming as an additional method of colour ordering. Here the Kelly-Judd report on Color: Universal Language and Dictionary of Names (1976) provides a penetrating insight into the subjective terminology by which one block of colour space can be distinguished from another. Some other novel colour order systems are also mentioned.     

Comparison of real colour gamuts using a new reflectance database

A large set of data, comprising the spectral reflectances of real surface colours, has been accumulated. The data comprise 16 groups with different materials and include 85,879 measured spectra. From these data, CIELAB colorimetric coordinates were calculated under CIE illuminant D50 and the CIE 1931 standard colorimetric (2°) observer. Several published colour gamuts including those developed by Pointer and ISO reference colour gamut [ISO Graphic Technology Standard 12640‐3:2007] were compared using the present data set. It was found that the Pointer gamut is smaller than the new real data in most of the colour regions. The results also showed that the ISO reference colour gamut is larger than the new real accumulated data in most regions. The present finding indicates that there is a need to derive a new colour gamut based on the newly accumulated data for common applications. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 442–451, 2014     

NCS and DIN notations for the OSA-UCS atlas samples

NCS (C/1931) and DIN (C/1931 and D65/1964) notations of the 558 OSA-UCS atlas samples are presented in two tables. One table provides the NCS and DIN notations for the 424 regular samples; the other for the 134 near-neutral (half-step) samples.     

Colorcurve and coloroid notations for the OSA-UCS atlas samples

Colorcurve (D65/1964) and Coloroid (C/1931) notations of the 558 OSA-UCS atlas samples are presented in two tables. One table provides the Colorcurve and Coloroid notations for the 424 regular samples; the other for the 134 near-neutral (half-step) samples. Colorcurve notations are derived from the OSA-UCS aim points, and Coloroid notations are derived from colorimetric data of the OSA-UCS samples contained in MacAdam's copy of the OSA-UCS colour atlas.     

Dynamic optimization of dissipative PDE systems using nonlinear order reduction

This article presents computationally efficient methods for the solution of dynamic constraint optimization problems arising in the context of spatially distributed processes governed by highly dissipative nonlinear partial differential equations (PDEs). The methods are based on spatial discretization using the method of weighted residuals with spatially global basis functions (i.e., functions that cover the entire domain of definition of the process and satisfy the boundary conditions). More specifically, we perform spatial discretization of the optimization problems using the method of weighted residuals with analytical or empirical (obtained via Karhunen-Loève expansion) eigenfunctions as basis functions, and combination of the method of weighted residuals with approximate inertial manifolds. The proposed methods account for the fact that the dominant dynamics of highly dissipative PDE systems are low dimensional in nature and lead to approximate optimization problems that are of significantly lower order compared to the ones obtained from spatial discretization using finite-difference and finite-element techniques, and thus, they can be solved with significantly smaller computational demand. The resulting dynamic nonlinear programs include equality constraints that constitute a low-order system of coupled ordinary differential equations and algebraic equations, which can then be solved with combination of standard temporal discretization and nonlinear programming techniques. We employ backward finite differences (implicit Euler) to perform temporal discretization and solve the nonlinear programs resulting from temporal and spatial discretization using reduced gradient techniques (MINOS). We use two representative examples of dissipative PDEs, a diffusion-reaction process with constant and spatially varying coefficients, and the Kuramoto-Sivashinsky equation, a model that describes incipient instabilities in a variety of physical and chemical systems, to demonstrate the implementation and evaluate the effectiveness of the proposed optimization algorithms.     

A model of colour vision for predicting colour appearance

A set of possible cone spectral sensitivity functions has been used to obtain combinations of responses that provide good predictions for loci of constant hue, simple criteria for unique hues, and good approximations to the NCS and Munsell schemes for surface colours, and to data on the appearance of spectral colours.     

Use of a predictive colour model for managing the colour appearance of two‐colour woven fabrics

The aim of this study was to implement a two‐dimensional colour appearance model for prediction of the colour values of weft threads when the optical mixing of a two‐colour woven structure had to match the colour appearance of a single‐colour reference woven fabric. Five single‐colour woven fabrics were woven from five threads of similar hue. One of the samples was chosen as a reference, for which the colour appearance was the goal to be achieved in the two‐colour woven fabrics prepared with the other available warp threads and newly dyed weft threads. The colour values of dyed weft threads were predicted by a two‐dimensional colour appearance model. With dyed weft threads, managing the colour appearance of the two‐colour woven fabric was enabled to achieve the colour values of the reference. In the results, colour deviations between the predicted and measured colour values of weft threads revealed some limitations to the colour appearance model and performance of the dyeing process. After the production of the two‐colour woven fabric, the colour appearance matched the appearance of the reference, resulting in deviations of ΔE_CMC(2:1) = 1.2‐7.8. Moreover, the differences between theoretically predicted and measured colour values of the two‐colour woven fabric were evaluated as small, ranging from ΔE_CMC(2:1) = 1.5‐1.9. The results demonstrated the efficiency of implementing the colour appearance model and the dyeing process of weft threads as an approach to achieve the defined colour appearance of two‐colour woven fabrics, which with small colour deviations matches the colour of a single‐colour reference.     

Survey of color order systems

Important modern color order systems accompanied by physical exemplifications (atlases) are surveyed; one of great historical interest, though not currently available, is included. The systems covered include the Munsell, Natural Color, OSA-UCS, DIN, Coloroid, and Ostwald systems. Their history, guiding principles, variables, and relation to the CIE system are described. Some of the interrelationships among the systems are then considered, specifically those between the Munsell system and the Natural Color and OSA-UCS systems. Implications for the consideration of international standard color order systems are mentioned.     

Vector-based modelling of colour difference: a pilot study of the DE2000 colour difference model

A novel approach to colour difference modelling is presented whereby for any given CMC (1:1) or CIE DE2000 ∆E, ∆C, ∆H, and ∆L colour difference, the equivalent CIE XYZ, L*a*b*, and L*C*h coordinate changes are derived by optimising the input RGB stimuli from which they are all calculated. Single-dimension L or C or H difference loci expressed in DE2000 difference units are thus generated, and the additive equivalence of tristimulus values is likewise projected forward onto each locus and also onto a set of CIE DE2000 three-unit ellipse boundaries. Using the datasets thus generated, it is then shown firstly that the derived ellipses have well-defined semi-axes, which explain the detailed orientation of the MacAdam ellipses in x,y,Y space. Unit CIE DE2000 difference is confirmed as a successful quantifying constant of visual difference over a wide range of chroma, hue, and lightness differences. As a constant, CIE DE2000 unit difference is shown to have a significantly variable value at high and low chroma: evidence is established for systematic changes in both chroma and hue difference sensitivity. A hitherto unresolved non-linearity is revealed in the C* dimension of L*C*h space that is not replicated in the CIE DE2000 model. The derived difference loci appear to specify physically reproducible experimental stimuli that could be used in the estimation of visual difference magnitude. Overall, the data derived by the new approach and presented in this paper increase the probability that a true vector model of the visual difference response may eventually be derived.     

A model of colour vision for predicting colour appearance in various viewing conditions

A previously published model of colour vision predicted the hues, lightnesses, saturations, and chromas of colours seen under a medium photopic level of illumination. This model has now been extended to provide, in addition, predictions of brightness and colourfulness, for both related and unrelated colours, at any level of illumination, whether photopic, mesopic, or scotopic. The model has also been extended to cover a wider range of stimulus intensities and the use of various backgrounds.     

Color order systems and architectural color design

In its first part, this article traces some outlines of the history of color order systems which bear upon the question of aesthetic color combinations (syntactic aspect). The second part defines the position of color in the field of architectural design (psychological, contextual, and structural aspect). The function and usefulness of color order systems in the process of architectural color planning and realization (pragmatic aspect) are discussed in the third and last part.