Color acceptance of direct dental restorative materials by human observers

The purposes of this study were to evaluate the CIELAB, CMC (2:1), and CMC (1:1) formulas to identify which provides the best indicator for acceptability of small color differences in the esthetic dental restorative materials, to determine if different groups of observers have different levels of acceptability, and to estimate the color difference that would indicate acceptability between a restoration and an adjacent tooth. The subject population of human observers was divided into four groups, each containing 12 subjects. The composition of the groups were: Group 1, dental auxiliaries and hygienists; Group 2, dentists; Group 3, dental materials scientists; and Group 4, patients. A color vision screening test was administered to each subject to ensure that only observers with normal color vision were evaluated. A composite resin color discrimination test was developed specifically for this study. This test was composed of six sets of discs fabricated from dental composite resin restorative materials. Each set consisted of one standard disc representing tooth color. In each set, six discs representing composite resin restorations were matched to the standard disc for a total of 36 pairings in the test. Color differences between the standard discs and the restoration discs were calculated in CIELAB, CMC (1:1), and CMC (2:1) color units. The subjects were asked to evaluate the composite resin materials as to acceptability of color differences between the disc pairs. The data were analyzed by logistic regression analysis for each observer and by each ΔE formula to generate receiver operating characteristics (ROC) curves. The areas under these ROC curves were calculated and ranked. ANOVA and Tukey's Studentized Range (HSD) Test were applied to the ranks. In regard to the acceptance of dental restorations based solely on color difference, the CMC (1:1) color difference formula gave better correlation than the CIELAB formula for small color differences in the esthetic dental restorative materials. There were significant differences found between the experiment groups in regard to acceptability of color differences using the CMC (1:1) and CIELAB formulas. The dental hygienist/auxiliaries group proved to be more discriminating in accepting differences between tooth and composite resin restorative material color than patients. The mean 50:50 ΔE replacement points for all subjects were 2.29 and 2.72 color units for the CMC (1:1) and CIELAB formulas, respectively. © 2000 John Wiley & Sons, Inc. Col Res Appl, 25, 278–285, 2000     

sRGB颜色空间与显示器呈色

sRGB颜色空间是显示器呈色遵循的一个标准颜色空间,具有一定的颜色控制规律。出厂时的显示器在白场色温、光通道阶调曲线和色域等方面不一定与sRGB相符。校准技术可调整显示器的白场和阶调曲线,并与sRGB标准相符合,但不能根本上改变色域。环境光照对显示器的呈色构成影响。实验结果表明,对一般的显示器,当其屏幕表面的光照度达100lx以上时,会明显压缩光通道的暗色调颜色层次,并在该颜色部位减小色域。     

陶瓷色料晶体结构及颜色

1前言无机颜料广泛应用于涂料、印刷、油墨、橡胶、纤维、造纸、化妆品、建材、皮革等众多领域。一般的无机颜料与主要用于陶瓷领域的陶瓷色料不同,这两者的产生、发展经过完全不同的过程,至今相互之间已几乎没有关系。釉的着色是陶瓷的独特技术,从试验和经验中产生的陶瓷色料,开始很难理解它们是由比较简单的矿物构成。在很长时间,一直处于“直觉”、“迷惑”状态,若没有相当的经验,很难配出与各色料适应的釉。早期的研究并没有引起人们的兴趣,但是战后由于结晶化学的发展,同时开发了ZrSiO4系、ZrO2系、SnO2系等新色料。这些新…     

Color signal coding: Color vision and color television

In this article the similarities in color coding between color vision and color television are discussed. The similarities go beyond the trichromacy shared by both systems. Color television transforms the initial color information before broadcasting in a manner similar to the opponent-color transformation in the retina. The coded broadcast is decoded in the television receiver.     

塑料色母粒色差原因和改进

色差是塑料色母粒制造过程中重要的质量控制指标。本文就色差产生的原因,从原材料、设备、操作工艺、环境、人为差错等方面着手,考虑到树脂和着色剂加工的性能,进行分析探讨,并提出改进措施。     

Color Stability of Clear and Opaque Titania Enamels Containing Various Color Oxides

A study was made of the spectrophotometric characteristics of a clear and an opaque titania-bearing enamel. Three and six per cent additions of green, blue, brown, and red oxides were made to the base enamels. After firing the enameled samples over a range of time and temperature, spectrcphotometric and X-ray data were obtained. The results indicate that the lack of stability of the opaque colored enamels is due to the change from a blue-white to a cream-white color on increased firing treatment. The addition of a cream component tends to shift the hue of the fired enamel toward the red end of the visible spectrum. The green and the blue colors were much less stable than the red. X-ray data show that the total anatase present decreases, which is evidence that a cream-white color developed. X-ray data did not indicate any change in crystal structure of the anatase, rutile, or color oxide. Titania present in the glass of the clear enamel did not cause color instability.     

Color sensitivity

This paper reports primarily upon tests of the color sense of about thirty men who have had large experience in the color grading of vegetable oils in terms of Lovibond glasses, nearly all of these men being members of the American Oil Chemists’ Society. Similar tests on five other observers are also included for comparison. All of the oil chemists were first tested by the Stilling Chart test, but the results by this test (although reported) are not the principal matter of interest. This test was regarded merely as preliminary, serving to discover any gross abnormality of color sense. The tests of specific interest relate to the observer’s ability to report correctly very small differences in Lovibond red at 35 yellow 7.6 red on the Lovibond scale, brightness diffences being eliminated so that the judgment depends, in effect, entirely upon the observer’s sensibility to difference in dominant wave length at equal brightness. The subject’s ability in this regard was tested by the well known psycho-physical method of “right and wrong answers.” The results for each observer are expressed so as to show the probability of his perceiving correctly given small differences in Lovibond red, under certain specified conditions. The chief results may be summarized as follows:

1. 1.
   A difference of 0.1 red at 35 yellow 7.6 red is perceivedwith certainty by only very few exceptional observers. However, this difference is perceptible in the sense that its presence does affect the observer’s judgmentin the average, although he is very doubtful of the reality of such a difference.     
   
   

汽车修补漆目视比色和色差仪颜色测量

介绍了颜色控制中颜色标准的确认,汽车修补漆调色过程中的颜色比对方法,包括颜色标准管理、目视比色和仪器测色方法,以及目视比色和仪器测色各自的优劣。     

Color space and its divisions

A synthesis of the author's recent work on color‐order systems and color‐difference evaluation is provided in context of current knowledge and practices. The development of a colorimetric model is demonstrated using Munsell “Celtic crosses” as a model of perceptual space. Issues surrounding color‐matching functions, unique hues, the Helmholtz–Kohlrausch effect, and lightness and chroma crispening are addressed, as is the difficulty of reconciling a difference‐based hue, chroma, lightness model with an Euclidean model. A new lightness scale and treatment of lightness crispening is proposed. The results indicate that, despite problems, relatively simple modified opponent‐color models provide good accuracy in predicting color‐order system and supra‐threshold small color‐difference data. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 209–222, 2001     

Color managing the third edition of Billmeyer and Saltzman's Principles of Color Technology

Commercial ICC‐compliant color‐management software was used to produce color‐managed CMYK‐encoded images for the third edition of Principles of Color Technology. Custom profiles were created for a Scitex Eversmart Pro flatbed scanner and a Kodak Approval proofing device. This enabled objects such as color‐order systems and colorimetric‐encoded, computer‐generated graphical images to be reproduced with reasonable colorimetric accuracy. The GretagMacbeth ColorChecker Color Rendition Chart was used as an independent verification target. Its printed reproduction had an average error of 4.2 ΔE (6.4 ΔE^*_ab). Colorimetric‐rendering device profiles enabled the visualization of the book's color gamut and of a calibrated visible spectrum. © 2002 Wiley Periodicals, Inc. Col Res Appl, 27, 360–373, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10083