Gamut evaluation of an n‐colour printing process with the minimum number of measurements

The aim of this study was to use a minimum number of measured colour patches to evaluate the colour gamut of an n‐colour printing process. Traditionally, the colour gamut of a printing system has been derived by printing and then measuring a gamut target for example, a profiling chart. For an n‐colour printing (printing with more than four process inks), it is desirable to know the colour gamut of the given set of inks without having to print a large number of test patches. Different spectral printer models were used to predict the gamut of a 7‐colour printing process. The colorant space was divided into sectors each containing four inks. For each printer model, the colour gamut of the each four‐ink sector was predicted. All sector‐gamuts were then combined to predict the overall colour gamut of the n‐colour process. This predicted gamut was then compared with the gamut obtained by measurement using a gamut comparison index (GCI). The Yule–Nielsen modified spectral Neugebauer (YNSN) model gave the best accuracy, at the cost of a larger number of input measurements, than other models. A combination of the Kubelka–Munk (KM) and YNSN models performed well with the fewest input measurements. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 408–415, 2015     

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     

A colour harmony model for two‐colour combinations

This study investigates harmony in two‐colour combinations in order to develop a quantitative model. A total of 1431 colour pairs were used as stimuli in a psychophysical experiment for the visual assessment of harmony. These colour pairs were generated using 54 colours selected systematically from CIELAB colour space. During the experiment, observers were presented with colour pairs displayed individually against a medium gray background on a cathode ray tube monitor in a darkened room. Colour harmony was assessed for each colour pair using a 10‐category scale ranging from “extremely harmonious” to “extremely disharmonious.” The experimental results showed a general pattern of two‐colour harmony, from which a quantitative model was developed and principles for creating harmony were derived. This model was tested using an independent psychophysical data set and the results showed satisfactory performance for model prediction. The study also discusses critical issues including the definition of colour harmony, the relationship between harmony and pleasantness, and the relationship between harmony and order in colour. © 2006 Wiley Periodicals, Inc. Col Res Appl, 31, 191–204, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20208     

Pretreatment effects on pigment‐based textile inkjet printing – colour gamut and crockfastness properties

The application of two commercial pretreatment agents, formulated to improve the performance of a six‐colour nano‐scale pigment ink set during the textile inkjet printing of cotton and polyester (PET) fabrics, was examined. An industrial scale printer, operating at 55 linear m/h and equipped with Kyocera printheads, was used to print on commercial fabrics (180 cm wide) prepared for digital printing. The work employed an industrial scale rather than a benchtop printer to enhance the utility of the results for a commercial environment. The colorimetric attributes of printed fabrics were recorded for the individual inks as well as for spot colour combinations generated using Dr. Wirth RIPMaster v11 software. Colour table profiles were also generated and the colorimetric values of inks were compared. Colour gamuts of inks on cotton and PET, including three‐dimensional volumes in the CIELab space, were examined to assess the role of pretreatment on the colorimetric properties of the printed substrates. It was found that the pretreatments enhanced the ink receptiveness, colour intensity and colour gamut of fabrics. Pretreatment of cotton resulted in a larger gamut and more vivid colours than on PET. However, wet and dry crockfastness results were found to be low. In this regard, Time‐of‐Flight Secondary Ion Mass Spectrometry analysis of fabrics printed in the presence and absence of pretreatment indicated that the low crockfastness arises from higher pigment levels on the surface of the pretreated fabric.     

Universal models of colour emotion and colour harmony

A new set of quantitative models of colour emotion and colour harmony were developed in this study using psychophysical data collected from 12 regions in the world, including Argentina, China, France, Germany, Hungary, Iran, Japan, Spain, Sweden, Taiwan, Thailand, and the UK. These data have previously been published in journals or conferences (for details see Tables 1 and 2 ). For colour emotion, three new models were derived, showing satisfactory predictive performance in terms of an average correlation coefficient of 0.78 for “warm/cool”, 0.80 for “heavy/light” and 0.81 for “active/passive”. The new colour harmony model also had satisfactory predictive performance, with an average correlation coefficient of 0.72. Principal component analysis shows that the common colour harmony principles, including hue similarity, chroma similarity, lightness difference and high lightness principles, were partly agreed by observers of the same region. The findings suggest that it is feasible to develop universal models of colour emotion and colour harmony, and that the former was found to be relatively more culture‐independent than the latter.     

Spectrophotometric measurement of human skin colour

This article focuses on human skin colour. Three different colour measuring instruments were used: a tele‐spectroradiometer, a de:8° and a 45°:0° spectrophotometers. They were used to measure 47 subjects who were divided into four skin groups: Chinese, Caucasian, South‐Asian, and Dark. Eight locations for each subject were measured. The spectral reflectance results were first compared. They all showed the “W” shape between the 550 nm and 580 nm as found by the other studies. Those from the tele‐spectroradiometer had an increase from 600 nm while the others were flatter. The colorimetric data calculated from the spectral measurements revealed similar patterns to describe the colour distribution of each skin group. It was found that two scales: whiteness‐depth, and blackness‐vividness could well describe these distributions. The results also showed systematic differences between the four ethnic groups, between eight body locations, between two genders, and between the measurements from the three instruments.     

Colour-distance judgement and the influence of the background in colour reproduction

The influence of the background in colour reproduction can be described in colorimetric terms by the use of corrections to the colorimetric scaling factors. This leads to transformation formulae that describe the change of chromatic adaptation, and also to an extended definition of the so-called “colour of the state of chromatic adaptation.” The method leads to an improved reconciliation between the specification of colour-rendering properties in both colour photography and multicolour printing and the visual evaluation. Certain problems in colorimetry may also become more easily understandable by the incorporation of such peripheral influences. Whereas the physiologically related scaling-factor corrections are of first-order importance, it is shown that stray-light effects, which are physical contributing factors, are only of the second order.     

Virtual colour: Communication standard and analytical tool

A number of problems have been identified with existing colour specification systems and their physical exemplifications: colorimetric conditions (illuminant, observer, spectrophotometer geometry, specular component inclusion/exclusion, etc.), restrictions of the notational system adopted, and limitations of the colour atlases themselves (sample size, sample error, sample range, etc.). Developments in computer science, and in particularly CRT displays and colour printing devices, now provide increasingly more affordable alternatives to traditional colour ranges and atlases. Techniques have been developed to increase the accuracy of printed colours relative to their CRT originals, and devices are manufactured to calibrate colour monitors. However, colour selection software developed to date is still primarily based on existing colour ranges and colour specification systems, or on a more general mechanism specific to an individual application. It is argued that basing such software on an existing model of colour specification inherits some of the problems of that system: notational methodology, means of representation, and atlas limitations. It is proposed that the restrictions imposed by such software be relaxed by providing a flexible method of constructing application-specific colour specification systems with conversion to a standardized notation for accurate colour communication. Furthermore, it is proposed that such a tool would be invaluable for the evaluation of human colour perception. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 204–211, May 1997.     

A study of colour emotion and colour preference. Part II: Colour emotions for two‐colour combinations

Eleven colour‐emotion scales, warm–cool, heavy–light, modern–classical, clean–dirty, active–passive, hard–soft, harmonious–disharmonious, tense–relaxed, fresh–stale, masculine–feminine, and like–dislike, were investigated on 190 colour pairs with British and Chinese observers. Experimental results show that gender difference existed in masculine–feminine, whereas no significant cultural difference was found between British and Chinese observers. Three colour‐emotion factors were identified by the method of factor analysis and were labeled “colour activity,” “colour weight,” and “colour heat.” These factors were found similar to those extracted from the single colour emotions developed in Part I. This indicates a coherent framework of colour emotion factors for single colours and two‐colour combinations. An additivity relationship was found between single‐colour and colour‐combination emotions. This relationship predicts colour emotions for a colour pair by averaging the colour emotions of individual colours that generate the pair. However, it cannot be applied to colour preference prediction. By combining the additivity relationship with a single‐colour emotion model, such as those developed in Part I, a colour‐appearance‐based model was established for colour‐combination emotions. With this model one can predict colour emotions for a colour pair if colour‐appearance attributes of the component colours in that pair are known. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 292–298, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20024     

Request for existing experimental datasets on colour emotion and colour harmony

The Technical Committee 1‐86 of the International Commission on Illumination on “Models of colour emotion and harmony” is requesting the submission of datasets for use in developing new models of colour emotion and colour harmony. The data should be submitted to the TC Chair, Dr. Li‐Chen Ou at the National Taiwan University of Science and Technology. © 2012 Wiley Periodicals, Inc. Col Res Appl, 2012     

The properties of multiple CMF determinations using alternative primary sets part I: Evidence and modeling

This article concerns William Thornton's single‐observer colour matching functions (CMFs). Alternative “prime colour” (or PC), “non‐prime” (or NP), and “anti‐prime” (or AP) wavelengths were used, and the measurements appear to challenge the basis on which conventional colorimetry predicts metameric colour matches. An analysis of Thornton's visual match data for alternative‐primary CMFs is presented. Using conventional colorimetric calculations, Thornton's articles establish failures of linear transformability between experimental data sets, failures of tristimulus sum prediction, and differences in CIE chromaticity for a set of strongly metameric stimuli that all match the same neutral reference stimulus. Error analysis using an optimization model is first used to confirm that Thornton's data represent a significant challenge to the standard colorimetric model. Thornton's assertion is supported that spectral power appears to be visually subadditive at NP and AP wavelengths compared with spectral power at the PC wavelengths. It is next shown that each of the individual failures of prediction can be eliminated by relatively minor adjustments to the relevant CMFs. However, each instance of failure required a different adjustment. Multiple and significantly incompatible linear adjustments of the CMFs are apparently needed to explain Thornton's results. The implication is that the visually additive value of the spectral stimuli used in the matches varies not only with wavelength but also as a nonlinear function of stimulus power. The implied variations in visual additivity become significant only at certain wavelengths. Thus a small and specific subset of strongly metameric light‐source matches, such as those chosen by Thornton, are required to reveal significant variations. Such spectrally localized variations have a minimal overall effect in the tristimulus sum predictions for surface‐colour matches using broadband stimuli. A detailed analysis of the central assumptions concerning additive colour mixing is given. It suggests that any super and subadditive visual effects revealed by Thornton's measurements can be accommodated within the standard colorimetric model by extending the model rather than by modifying the CMFs. An extension is proposed in which any possible super‐ or subadditive phenomena are modeled by a redefinition of the units of visual additivity, using a spectral‐level precursor transform. Its intent is to equate the additive properties of all possible incident stimuli numerically, prior to manipulation using the Standard Model. An appropriate methodology is also described for confirming measuring and classifying any spectrally distinct super and subadditive effects. Under The Heading for Prediction Failures the methods described are applied to Thornton's data. They reveal consistent evidence of additivity differences that are both wavelength and stimulus power dependent. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 273–284, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20022     

Colour and ergonomics: On the selection of a “colour of the year”

The key role of colour in ergonomics has been emphasized by a number of researchers and design professionals. Although several research studies have been published regarding the use of colour in ergonomics, there are still some areas that need to be considered. The issue of deciding a “colour of the year” is an example, which represents a new challenge for researchers in the field of ergonomics. This is of particular interest considering the fact that the nature of research on the selection of a “colour of the year” is generally based on user experience. This paper argues that ergonomics should play a more prominent role in this field to ensure better user experience and performance. This paper highlights specific areas that need further study and development.     

Developing the methodology of colour gamut analysis and print quality evaluation for textile ink‐jet printing: Delphi method

This research used the Delphi method to investigate current colour gamut analysis methods, which is a critical component of colour management systems (CMS). Thirteen ink‐jet printing experts were interviewed to understand how they manage colour and their process for analysing and comparing colour gamut. A significant result of this study was the development of a four‐stage process model for colour gamut analysis and print quality evaluation for textile ink‐jet printing. The optimal process model was verified and approved by experts. This study uncovered an industry initiative toward the improvement of CMS for more accurate colour matching, a need to stabilise variables in the manufacturing process, and a need to standardise related tests and evaluations. The study also revealed new CMS software and technologies developed for ink formulation and pre‐/post‐treatment methods to facilitate high quality production in textile ink‐jet printing.     

Colour meaning and context

This study compares semantic ratings of colour samples (chips) with those of the same colours applied to a variety of objects. In total, 25 participants took part in the colour‐meaning experiment, and assessed 54 images using five semantic scales. In Experiment 1, simplified images (coloured silhouettes) were used whereas in Experiment 2 real images were used. In this article, the terms “chip meaning” and “context meaning” are used for convenience. Chip meaning refers to the associated meanings when only isolated colour chips were evaluated while context meaning refers to colour meanings evaluated when colours were applied to a variety of product categories. Analyses were performed on the data for the two experiments individually. The results of Experiment 1 show relatively few significant differences (28%) between chip meaning and context meaning. However, differences were found for a number of colours, objects, and semantic scales i.e., red and black; hand wash and medicine; and masculine‐feminine and elegant‐vulgar. The results of Experiment 2 show more significant differences (43%) between chip meaning and context meaning. In summary, the context sometimes affects the colour meaning; however, the degree to which colour meanings are invariant to context is perhaps slightly surprising. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 450–459, 2017     

Properties of ink‐jet printed,ultraviolet‐cured pigment prints in comparison with screen‐printed,thermo‐cured pigment prints

A collection of printed fabrics for men’s shirts was designed and prepared using computer‐aided design/computer‐aided manufacturing technology. The colours for designs were ink‐jet printed on cotton fabrics with pigments and ultraviolet‐cured. These prints represented the target colours for subsequent flat‐screen printing, which was performed using pigment printing pastes and thermal curing. For an exact transfer of colours of the ink‐jet‐printed standard into the screen‐printing process, a computer recipe prediction method was used. A comparison of colorimetric parameters of fabrics printed with both printing techniques shows minimal and acceptable differences in the CIELab colour values. A comparison of colour fastness properties proves that very good colour fastness is achieved on the pigment‐printed fabrics produced with both printing techniques. The flat‐screen‐printed fabrics show better colour fastness to washing, perspiration and rubbing, while ink‐jet‐printed fabrics show better colour fastness to dry‐cleaning and light. The fabrics printed with both printing techniques have high rigidity and non‐elastic properties. The mechanical and physical parameters are strongly dependent upon the amount of the dry substance of the printing media applied on the cotton fabric surface, which is higher on screen‐printed fabrics. The ink‐jet‐printed fabrics show better air permeability than flat‐screen‐printed fabrics.     

A colour study approach through colour measurements on slides of art paintings

The present work deals with the problem of colorimetric fidelity of digitized colour slides representing fine art paintings. This consists of a comparison between colour measurements provided by spectrophotometry on fourteen original colour samples, which are uniformly painted square-shaped patches and those taken on digitized colour slides of the same colour samples. Digital acquisition of slides were performed by a 3CCD detector and a combination of colour correction filters. The obtained R_cam, G_cam, and B_cam values were then corrected and transformed into X_cam, Y_cam, and Z_cam values based on the CIE 1931 XYZ colorimetric system. The colour difference, , in the CMC uniform colour space is also calculated and found to be equal to seven, = 7, in average value, when colour compensating filters are used. This method is finally applied to four art works reproduced on different slides, and colour results were qualitatively compared as an indication to these resulting from Ostwald disk and saturation diagrams of previous research studies related to paintings that are created by the same artists. This comparison led to the same conclusions that were already proposed by the previous researchers. The results clearly demonstrate the contribution of the method to a computer-aided study of art works through image data banks that are realized by slides, taking into consideration, however, that this study consists of a first approach, offering a promising solution to the problem of colour accuracy of slides. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 326–334, 1997     

Ink-jet printing of cationised cotton using reactive inks

The ink-jet printing properties of cotton cationised with 2,3-epoxypropyltrimethylammonium chloride have been studied. Cyan, magenta, yellow and black reactive inks were used to print untreated and cationised cotton fabrics. The effect of cationic reagent concentration, steaming time, ink (colour) and print resolution were investigated, together with possible differences between the behaviour of the four inks. Colour yields, staining of the white grounds, penetration behaviour, print quality and fastness properties were evaluated.     

Colour‐appearance modeling using feedforward networks with Bayesian regularization method. Part II: Reverse model

In Part I of this article, the development of a multilayer perceptrons feedforward artificial neural network model to predict colour appearance from colorimetric values was reported. Bayesian regularization was employed for the training of the network. In this part of the article, the reverse model, that is, the perdition of colorimetric values from the colour appearance attributes is reported using the same neural network design methodology developed in Part I. This study should contribute to the building of an artificial neural network–based colour appearance prediction, both forward and reverse, using the most comprehensive LUTCHI colour appearance data sets for training and testing. Good prediction accuracy and generalization ability were obtained using the neural networks built in the study. Because the neural network approach is of a black‐box type, colour appearance prediction using this method should be easier to apply in practice. © 2002 Wiley Periodicals, Inc. Col Res Appl, 27, 116–121, 2002; DOI 10.1002/col.10030     

A study of colour emotion and colour preference. Part III: Colour preference modeling

In this study three colour preference models for single colours were developed. The first model was developed on the basis of the colour emotions, clean–dirty, tense–relaxed, and heavy–light. In this model colour preference was found affected most by the emotional feeling “clean.” The second model was developed on the basis of the three colour‐emotion factors identified in Part I, colour activity, colour weight, and colour heat. By combining this model with the colour‐science‐based formulae of these three factors, which have been developed in Part I, one can predict colour preference of a test colour from its colour‐appearance attributes. The third colour preference model was directly developed from colour‐appearance attributes. In this model colour preference is determined by the colour difference between a test colour and the reference colour (L*, a*, b*) = (50, ?8, 30). The above approaches to modeling single‐colour preference were also adopted in modeling colour preference for colour combinations. The results show that it was difficult to predict colour‐combination preference by colour emotions only. This study also clarifies the relationship between colour preference and colour harmony. The results show that although colour preference is strongly correlated with colour harmony, there are still colours of which the two scales disagree with each other. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 381–389, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20047