What's New?
Updated annual meeting info.
Baltimore, Sept 08
Menu troubles?
Use the site map.
ISCC Members Bodies |
Back to Issue 432
|
Color Research and Application
In This Issue, April 2008
Sadly we open this issue with another obituary. Tarow Indow, who served on the editorial board of this journal since its inception, died last fall. Just a week before his death I had sent him the acceptance for a manuscript, which he had been working on. While I am afraid that he never read the letter since he was in the hospital, his friend and co-author has agreed to see the article through publication. It will appear in a future issue this year. For now, please see the tribute in this issue that was written by A. Kimball Romney.
Our first two articles come from the National Institute of Standards and Technology (NIST) in the United States. In “NIST 0:45 Reflectometer,” Maria Nadal, Edward Early, William Weber and Robert Bousquet describe the design of a new instrument. The primary purpose of the 0:45 reflectometer is to enhance the capability of NIST to provide standards to the color and appearance user community. This automated instrument can measure up to 20 specimens at a time. Edward Early and Maria Nadal present the “Uncertainty Analysis for the NIST 0:45 Reflectometer” in the second article.
Colorimetry as we know it is based on the CIE system proposed in 1931 and has worked well for many applications since its inception. However, over the years there have been numerous articles, most notably those by William Thornton, pointing out that the system breaks down in certain cases. Our next article reports that CIE colorimetry breaks down when lights produced by narrow band RGB-LEDs are matched with broad-band lights. Péter Csuti and János Schanda performed a color-matching experiment where matches in a various of parts of the chromaticity diagram were made then examined to determine the magnitude of the discrepancy between what was observed and calculated. In “Colour matching experiments with RGB-LEDs” they report that differences between visual and instrumental matches increase as one moves in the chromaticity diagram from yellowish white lights towards greenish and bluish lights. They also report that if the CIE color matching functions are replaced by color matching functions based on the newly defined cone fundamentals from the report from CIE TC 1-36 enables a much better prediction of the matches to be made. When a transformation of these fundamentals to a space similar to the CIE XYZ space is applied, the difference between the visual match and its instrumental prediction decreases by a factor of two or even more. Therefore they recommend the use of a cone fundamental-based colorimetric system for LED colorimetry.
Our next article comes to us from Russia. Professor Douglas Bowden, M. D., of the Department of Psychiatry and Behavioral Science at the University of Washington Medical School in Seattle, Washington provided the translation, “The Representation of Colors in Spherical Space.” In the article the authors Yurii Leonov and Evgenii Sokolov describe a formal mathematical model of color space, in which color differences are equal to the chord distance between points on the surface in the spherical space. Unlike other models, this one model unites brightness, saturation and hue as expressed in the empirical Munsell and Natural Color systems; complementary colors; large color differences; and contrast effects.
Last year in this journal Yoshinobu Nayatani and Hideki Sakai made a proposal of a new concept for color-appearance modeling, where all the attributes are mutually independent. They called the group of models “In-CAM” for Integrated Color Appearance models, because the fields of applications in both colorimetric engineering and artistic color design can be integrated. Now in this issue the same authors are presenting “An Integrated Color-Appearance Model using CIELUV and Its Applications” as a simple example of how such In-CAM models work. They expect other better In-CAM models to be developed in the future.
In color reproduction, scanners and digital cameras are becoming widely used in areas where accurate reproduction of color is important. In order to obtain a faithful color reproduction, the imaging device needs to be characterized. Colorimetric characterization transforms the device responses (usually red, green, and blue) into colorimetric tristimulus values, while spectral characterization converts them into spectral reflectance. Compared with spectral characterization, the main disadvantage of colorimetric characterization is that it can only obtain tristimulus values under a certain illuminant. As the responses of the imaging device are generally nonlinear to scene radiance, the optoelectronic conversion functions (OECFs) should be obtained or recovered before color characterization. Traditionally the OECFs are obtained from standard gray samples. However, gray samples are sometimes unavailable when conducting color characterization. Therefore in our next article, “Estimation of Optoelectronic Conversion Functions (OECFs) of Imaging Devices,” Hui-Liang Shen, John H. Xin, Dong-Xiao Yang Dong-Wu Lou propose an efficient method for recovering OECFs by using non-gray samples, based on the finite-dimensional modeling of spectral reflectance and the 2nd order polynomial fitting of OECFs. Their proposed method should be particularly useful in colorimetric and spectral characterization of imaging devices by using custom-made color samples in textile or other industries, when standard gray samples are not available and not easily made.
Generally as people age their color perception changes, in particular as cataracts develop. The changes are in terms of three factors: color, brightness, and haze. The color change, due to the changes of the transmittance of the crystalline lens in particular in the blue region, and brightness changes, due to the an overall decrease in transmittance, have been studied widely. But generally the changes resulting from haze have not been explored in such depth. Mitsuo Ikeda and Tomoko Obama report on a study of the effects of haze on the color perception in “Desaturation of Color by Environmental Light in Cataract Eyes.” As the title suggests, they confirmed that environmental light which is generally white, gets scattered through the lens of cataract eyes, (or when wearing goggles to simulate cataracts) producing a white haze that generally makes colors appear less saturated as compared with the perception of normal younger observers. This was confirmed by both young observers wearing special goggles, and by comparisons of vision with an elderly observer before and after cataract surgery. Thus the effects of environmental light should not be overlooked when studying the vision of those people with cataracts.
For our final article in this issue we move to the field of textiles. Obviously the first textile coloration was using natural dyes, but then as synthetic dyes were developed stronger brighter colors became available. Now there is a renewed interest in natural dyes, which are considered fashionable for the environmentally conscious user. In the “Color Analysis of Natural Colorant-Dyed Fabrics” Ju-Yeon Yi and Eunjou Cho report on a study to investigate color characteristics for a given large set of natural colorants-dyed fabrics based on the Munsell color notations. They analyzed the tones of dyed fabric in terms of Munsell notation of hue, value, and chroma and identified the effects of mordants on the colorimetric properties of the fabrics for 350 dyed fabrics. In this way they hope to provide a systematic description of natural-dye fabric colors for general use and to use as a guide for the development of future colors.
We close this issue with notices about several CIE publications: CIE S009:2006 Photobiological Safety of Lamps and Lamp Systems; CIE S014-4:2007 CIE 1976 L*, a*, b* Colour Spaces; CIE S019:2007 Photocarcinogenesis Action Spectra; and CIE 180:2007 or Developing Countries ISBN 978 3 901 906 61 9. Also, we have a report on the AIC Midterm Meeting in Hangzhou, China in July 2007, and an announcement about the forth coming CIE Expert Symposium on Advances in Photometry and Colorimetry. Finally there is a significant Erratum including all the figures for the article “New Method for Measuring an Optical Property of a Printed Sample on FWA-Treated Paper” by Kenji Imura.
|
|
