ICC-color Management tools claim to give both accurate and consistent results. However, using these tools of distinct manufacturers, different results are likely to occur even if the same parameters are given. Obviously the manufacturers do not focus on the same criteria doing their optimizations, which leads to the fact that each tool has its own strengths and weaknesses. In this study, new methods for comparing ColorManagement tools were evaluated, and with these methods, ICC profiles generated by five CM tools of current leaders on the market were investigated in order to point out their weaknesses and strengths. In addition, the influence of using various ColorMatchingModules (CMM) was tested. For the generation of each ICC profile, the same measurements (ISO 12642 equals ANSI IT8. 7/3 target of Iris InkjetPrinter) were used. Since the standardized ISO 12642 file format, in which the measurement data are stored, was not accepted by each of the tools, the data-file had to be converted to proprietary formats. The investigated quality aspects were accuracy, consistency and smoothness, with ΔEab2 and ΔE943 taken as the criteria. For each aspect, performance was visualized by mapping the ΔE values to pseudo colors, giving a very intuitive view on the investigated subject. Results showed that ColorManagement tools indeed achieved good color fidelity, especially if generated as large profiles.
KEYWORDS: Curium, CMYK color model, Manufacturing, Color management, Color difference, Standards development, Visualization, Data conversion, Image processing, Data modeling
Color Management (CM) tools claim to give both accurate and consistent results. However using CM tools of distinct manufacturers, different results are likely to occur even if the same parameters are given. Obviously the manufacturers do not focus on the same criteria doing their optimizations, which leads to the fact that each CM tool has its own strengths and weaknesses. In this study, new methods for comparing CM tools were evaluated, and with these methods, ICC profiles generated by five CM tools of current leaders on the market were investigated in order to point out their weaknesses and strengths. In addition, the influence of using various CM modules (CMM) was tested. For the generation of each ICC profile, the same measurements were used. Since the standardized ISO 12642 file format, in which the measurement data are stored, was not accepted by each of the tools, the file had to be converted to proprietary formats. The investigated quality aspects were accuracy by each of the tools, the file had to be converted to proprietary criteria. For each aspect, performance was visualized by mapping the (Delta) E values to pseudo colors, giving a very intuitive view on the investigated subject.
The quality control of fabrics makes still use of visual assessments in cases where the highest degree of matching between batch and reference samples must be achieved, e.g. in the field of 'mix and match' garments. The reasons for the failure of current color measuring instruments were investigated, and it was found that among others, the most important aspects were the vivid nature of a textile whose color cannot be completely described by just a single measurement, and the differences of the conditions of viewing and measuring. A multispectral scanner which was originally designed for faithfully digitizing originals such as textiles and paintings was used to measure the colors of fabric samples. Since the spectral scanner was not limited to a standard measuring geometry, assimilation of the viewing and measuring geometries was possible. The system was run through a field test in the quality control with a large manufacturer of fabrics. It turned out that, unlike with conventional spectrophotometers, a very good congruence between the pass/fail decisions of the multispectral system and experienced persons could be achieved.
The purpose of this study was to identify the performance of novel realized color sensors manufactured in thin film technology and to compare the results with simulations. In a previous study, a novel technology of three- and six-channel color sensors was presented. The performance of the sensors was tested in simulations and compared to other sensors for different characterization methods (polynomial regression and smoothing inverse). Now, these method are supplemented by a new linear programming method. Moreover, practical experiments with real color capture have been conducted.
Today, the characterization of scanners combines properties of both the scanner and the medium. A different method is proposed here. If the characterization of the scanner is carried out spectrally, it is not specific to a medium and the medium properties can be acquired separately. The drawback of this approach is the lack of a simple solution to determine spectral properties of a scanner. Therefore, a method to estimate the spectral properties of a scanner by scanning a single test chart is proposed.
A novel sensor concept for the detection of the fundamental components of visible light has been developed. The multi- channel sensors (3-, 4- and 6-channel detectors) based on three and four stacked amorphous thin film detectors are color moire or color aliasing free due to their vertical integration. The color separation is performed in the depth of the structure without using optical filters. The developed 3- and 4-channel detectors can be read-out with one shot whereas the color information of the 6-channel detector can be read- out with two shots. The sensors are colorimetrically characterized in order to gain further optimization criteria concerning the improvement of the sensor performance. The presented characterization model facilitates the quantification of color errors with regard to the human perception. Furthermore, the color errors of amorphous thin film sensors are compared with a commercial color CCD camera and a BiCMOS color-sensor.
This paper describes a new type of multichannel color sensor with the special property of having all channels per pixel at the same spatial location one on top of the other. This arrangement is accomplished by stacking three amorphous thin film detectors on a glass substrate. It has the advantage that the color noire effect is avoided which produces large color errors when objects of high spatial frequency are captured with a multi-channel sensor array. The new technique enables the design of a three-channel sensor as well as a six-channel sensor. In the latter case, color is captured in two 'shots' by changing the bias voltages. The colorimetric characterization of the sensors is presented, including multiple polynomial regression both for tristimulus and spectral reconstruction, and the smoothing inverse for spectral reconstruction. The result obtained with different types of regression polynomials, different sensors, and different characterization methods are compared. The results show that the three-channel color moire free sensors are able to produce good accuracy, while the six-channels' performance is striking.
KEYWORDS: Distortion, Data modeling, Optimization (mathematics), Printing, Linear filtering, CMYK color model, RGB color model, Signal processing, Copper, Error analysis
This paper describes the analytical representation of the color gamut surfaces of arbitrary print processes. Such a method was published earlier, but has now been improved and tested against a number of different print processes. Moreover, an algorithm to determine the model parameters that reflect the characteristics of a considered print process is described.
In this study, gamut mapping between real print processes was investigated. The processes were supposed to have equal lightness ranges, hence no lightness mapping applied. Several chroma mapping methods modifying and not modifying lightness were systematically evaluated. Pure clipping of chroma resulted as the best technique when lightness was left untouched. However, a few images required adjustments of lightness in order to retain higher chroma. These investigations were used to gain practical experience with anew, analytical color gamut representation recently published. THE new representation method displayed no kind of anomalies and hence proved to be fully practical.
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