Different industries are usually faced with computer COLOR MATCHING as an important problem. The most famous formula, which is commonly used for recipe prediction is based on the Kubelka-Munk (K-M) theory.Considering that spectrophotometer’s geometry and its situation influence the measured spectral values, the performance of this method can be affected by the instrument. In the present study, three spectrophotometer geometries including 45/0, d/8 with specular component included mode and d/8 with specular component excluded mode were compared in the case of recipe prediction of textile samples using K-M theory. Comparing the applied measuring situations, the COLOR MATCHING results obtained from d/8 geometry in SCE mode were far better than the others, while 45/0 geometry gives inferior performance which may be caused by the textured surface of textile fabrics.

The aim of the present study was to investigate and compare the performance of various COLOR MATCHING procedures inclusive of COLOR MATCHING based on Allen's rough match and an iterative procedure using the CIELAB COLOR difference formula, spectrophotometric procedures such as McGinnis least square method, iterative method, weighted iterative method and spectrophotometric COLOR MATCHING based on fundamental COLOR stimulus. To this end, 165 samples were dyed. Initially, the comparisons were made theoretically on the basis of COLOR differences and indices of metamerism. Additionally, such comparison was extended practically by dyeing 24 real dyed samples. Practical results were in good agreement with the theoretical results, showing a relatively better performance of the spectrophotometic COLOR MATCHING procedure based on the fundamental COLOR stimulus. J. COLOR Sci. Tech. 7(2013), 75-83© Institute for COLOR Science and Technology.

In digital COLOR imaging, it is of interest to transform the COLOR scene of an image to the other. Some attempts have been done in this case using, for example, lab COLOR space, principal component analysis and recently histogram rescaling method. In this research, a novel method is proposed based on the Resenfeld and Kak histogram MATCHING algorithm. It is suggested that to transform the COLOR scene between two images, the histograms of the three R, G and B channels of the input image would be matched to the corresponding histograms of the destination one. The performance of the introduced method was investigated for several images. The obtained results indicated that this method is well capable of transforming the COLOR scene between images.

The traditional method for studying non-stationary signals is spectrogram based on the short-time Fourier transform (STFT). The well known limitation of the STFT is the inherent trade-off between time and frequency resolution. The Wigner-Ville (WV) distribution has the best time-frequency resolution, but its draw back is generating cross-terms. The MATCHING pursuit (MP) distribution based on using the Gaussian atom is always positive, does not include crossterm, and has convenient resolution. In this paper, we have shown in addition to the known properties, the MP distribution can also remove the additive noise inherently. On the other words, we are able to remove the noise just by limiting the algorithm iterations and without paying any additional cost. Although the MP distribution based on using the Gaussian atoms is always positive and it has convenient resolution, according to the MP the time marginal and the frequency marginal will not be obtained accurately. In this paper, it has been shown that by implementing the minimum cross entropy (MCE) technique according to the MP distribution as a priory positive distribution, the new extracted distribution has the most similarity to the MP distribution and it also satisfies the correct time and frequency marginal.

Background and Aim: One of the most challenging procedures in restorative dentistry is fitting the COLOR of the restoration to the tooth. The main purpose of this study was to determine the ability rate of COLOR MATCHING among the students of Yazd faculty of dentistry in December 2004.Methods and Materials: In this descriptive study, 127 dental clinical students of Yazd faculty were participated. Age, gender, wearing eyeglasses or lens and the year of starting the dental faculty were assessed as variable. Heliomolar composite with 16 COLORs was used to make the shade guide and 6 COLORs of the same composite were used as test group. The students were matched the shade guide with the test group in similar conditions. The data was analyzed by t, ANOVA and LSD test.Results: Mean truth definition of all COLORs in 20-29 years old students were 3.86 and in 30-40 years old group were 3.38 and there was no significant differences between them. Mean truth definition in male group was 3.57 and was 3.91 in females. There were no significant differences between them. Mean truth definition in all of the COLORs by students without eyeglasses or contact lens were 3.98 and the other group was 3.55 which was significantly differences (P=0.023). The difference between the entrance year for mean truth definition of all COLORs was significant (P=0.016).Conclusion: In this study, the students whom specially wear photochoromic eyeglasses or contact lenses were lower truth COLOR definition, but age and gender had no effect on truth COLOR definition.

Introduction: One of the most important factors in survival rate of implant - supported crowns is the adaptation of crown and abutment. In this study the COLOR MATCHING and aesthetic evolution of anterior maxillary crowns was evaluated.Materials and Methods: For this in vitro investigation 20 CAD/CAM crowns (group 1), 20 IPS e. max crowns (group 2) and 20 metal ceramic crowns were made for the maxillary central incisor of a phantom head. The silicon replica technique was used for the measurement of marginal and internal gaps. For COLOR MATCHING A2 shade tab was chosen of classical VITA shade guide as a reference shade. Visual and instrumental COLOR evaluation were done for abutment - supported crowns and those crowns without abutment support. ANOVA, Tukey HSD and Pairedt test were used for data analysis (a=0.05).Results: The smallest marginal gap was for CAD/CAM crowns (86/07m). Mean marginal gap for other groups had no statistically significant difference (p value=0/916). All groups had no statistically significant difference for internal gap (p value=0/1). For abutment supported crowns the best COLOR MATCHING result (visual & instrumental) was for CAD/CAM crowns. COLOR MATCHING in other groups had no statistically significant difference (p value=0/239, p value=0/872). COLOR MATCHING evaluation approved the effect of titanium abutment on the COLOR of group 1 & 2 crowns.Conclusion: All result for all groups were clinically acceptable. The CAD/CAM crowns had the best result in both two factors.

The COLOR of the blends of pre-COLORed fibers depends on the ratio of each fiber in the blends. Some theories have been introduced for COLOR MATCHING of blends of pre-COLORed fibers. Most however, are restricted in scope and accuracy. Kubelka and Munk presented the most applicable theory, which is still used in industry. In this work, the classical Kubelka-Munk method for COLOR prediction of a series of grays, prepared from different ratio of black and white is compared with new technique, which apply neural networks. Thirteen different blends with different ratio of virgin and black fibers were prepared. The reflection of samples was measured and then a two layers network was designed. The modified back-propagation learning strategy was applied. The Sum of Squares Error was calculated for evaluation of methods. Results showed better prediction for networks in comparison to Kubelka-Munk algorithm.