These are internal Munsell Laboratory reports, published only electronically, that might be of interest. Most abstracts are available by clicking the title. There are links to the full PDF files with each abstract.
Practical Spectral Imaging Using a Color-Filter Array Digital Camera,
by Roy S. Berns and Lawrence A. Taplin, July 2006>br>
Imaging is an important technique in the scientific examination of art. Its main use has been for visual documentation. Photographs have long been used to document condition before and after transit, microscopic examinations, conservation treatments, and so on. They are used to enable color reproductions in books and from the Internet. Images using materials with spectral sensitivities in such non-visible regions of the electromagnetic spectrum as infrared and X ray are equally important to the visible spectrum. Although images are used to record scientific examinations, they are used infrequently as an analytical tool, that is, the amount of colorant in a photographic material would be used to relate to physical properties of the art. In contrast, astronomy, remote sensing, and medicine have exploited this capability for many years. The advent of digital imaging offers increased opportunities to exploit images for the scientific examination of art. A research program is underway at Rochester Institute of Technology to develop an image-acquisition system that records reflection information as a function of wavelength. The system initially is limited to the visible region. The program is known as the Art Spectral Imaging Project and the program is documented at www.art-si.org.
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Performance Evaluation of Profile Maker Professional 5.0 ICC Profiling Software,
Pravin Rao, Mitchell R. Rosen and Roy S. Berns, January 2005

Experiments were undertaken at the Munsell Color Science Laboratory to evaluate the colorimetric performance of camera, display and printer profiles produced through the Gretag Macbeth Profilemaker Pro ICC profiling software version 5.0. ICC profiles were generated for a Sinarback54 M mega-pixel camera, an IBM T 221 LCD monitor and an Epson 7600 Ultrachrome inkjet printer. Errors were expressed in CIEDE2000 color-difference values. The camera profile showed the poorest colorimetric prediction capability with errors as large as 17.89 CIEDE2000 units over a test set. The display model was the most accurate with no error exceeding CIEDE2000 of 3.60 for its set of test colors. In between was the printer with a maximum error of 6.27 CIEDE2000. Smoothness of the color look up tables contained within the ICC profiles for each device was also investigated. Color look up table smoothness investigations revealed that the camera ICC profile showed the greatest deviation from smoothness while the other profiles exhibited reasonable smoothness.
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Methods of Spectral Reflectance Reconstruction for A Sinarback 54 Digital Camera,
Yonghui Zhao, Lawrence A. Taplin, Mahdi Nezamabadi, and Roy S. Berns, December, 2004

There is an urgent need to build digital image databases with adequate colorimetric accuracy for museums, achieves and libraries. Traditional colorimetric imaging suffers from the possibilities of metameric problem, while spectral imaging can facilitate accurate tristimulus estimation and possibilities for spectral reconstruction of each pixel. Spectral image archives can be used to render accurate images both spectrally and colorimetrically to the original target for any illuminant and observer. The most convenient and practical capture system for spectral imaging combines a commercial trichromatic camera with two absorption filters to define image spectrally. Two images were taken for each target; so six-channel multichannel images were obtained. Three methods of spectral color reproduction were evaluated: pseudoinverse method, canonical correlation regression (CCR), and Matrix R method. The CCR method can obtain the highest spectral accuracy among these methods, just because it incorporates fifteen crossproduct terms in the simulation. The Matrix R method can reach the same spectral accuracy as the pseudoinverse method, and the spectral accuracy of both methods could be improved if they also use the same cross product terms. On the other hand, the Matrix R can achieve the best colorimetric accuracy for a certain combination of illuminant and observer. Thus, the Matrix R is a very promising method for achieving artwork images with sufficient spectral and colorimetric accuracy.
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The Perception of Color as Espoused by Ralph M. Evans of the Eastman Kodak Company and its Extension to What is Known Now and What Remains to be Seen,
Rod Heckaman and Mark D. Fairchild, December, 2004

This paper is intended as an in depth review of Ralph Evans' book, The Perception of Color, posthumously published in 1974, that focuses on what Evans noted as the central thesis of the book -- that the perception of color in all but the most simple of contexts is the sum of not just the three fundamental perceptions of hue, lightness, andchroma, but five in total. The single thread that carries the development of this thesis throughout this book and Evans' work is his discovery, at least to him and his colleagues, of a new and unique perception of what he terms brilliance. Hence, the underlying thread of this paper is to relate, in hopefully a simple, easily understood manner, Evans' vivid descriptions of how brilliance is invoked and his analysis of its affect. Finally, Evans' central thesis is compared to what we know today about the appearance of color, and based on his work in brilliance, whether or not the study of brilliance can provide relevance to the understanding of vision.
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Modifications of a Sinarback 54 Digital Camera for Spectral and High-Accuracy Colorimetric Imaging: Simulations and Experiments,
Roy S. Berns, Lawrence A. Taplin, Mahdi Nezamabadi, and Yonghui Zhao, June 2004

A search technique was used to identify sets of colored glass filters that could be placed in the optical path of the Sinarback 54 camera system resulting in improved color accuracy compared with a production unit and the ability to perform spectral estimation. A green and blue filter, each a pair of filters, were identified and constructed from Schott glass. RGB images were collected through these two filters resulting in six image planes. Using the Gretag Macbeth ColorChecker DC and a custom target of blue artist pigments, a transformation was derived that converted digitally flat-fielded and photometrically-linearized camera signals to estimated spectral reflectance factor. The combination of using these two filter "sandwiches" and appropriate mathematics resulted in more than a twofold improvement in color and spectral accuracy compared with the production camera. The average colorimetric and spectral performance is shown in the following bar graphs for the calibration targets and independent-verification targets, the Esser TE221 test chart, a custom target of artist pigments made using the Gamblin Conservation Colors, and the traditional GretagMacbeth ColorChecker ColorRendition chart. These results indicate that it is possible to achieve excellent color accuracy and acceptable spectral accuracy using a color-filter array sensor.
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Pigment Selection Using Kubelka-Munk Turbid Media Theory and Non-Negative Least Square Technique,
 Mahnaz Mohammadi, Mahdi Nezamabadi, Lawrence A. Taplin, and Roy S. Berns, June 2004

This report describes a process of pigment selection for reconstructing the Gamblin Conservation Colors and various artist pigments dispersed in linseed oil. Single-constant Kubelka-Munk (K-M) turbid media theory and a non-negative least square (NNLS) optimization technique were employed in this experiment. Eleven pigments were selected as representative of the 30-pigments Gamblin Conservation Colors. These werequinacridone red (PV 19), venetian red (PR 101), cadmium red medium (PR 108), cadmium yellow medium (PY 37), indian yellow (PY 83), chromium oxide green (PG17), phthalocyanine green (PG 7), phthalocyanine blue (PB 15:2), cobalt blue (PB 28),titanium dioxide white (PW 6), and ivory black (PBK 9). The report is classified into four sections:

A. Preparing the samples and spectral measurements
B. Pigment characterization
C. Color matching and pigment selection
D. Verification of selected pigments with unknown samples
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Verification of the Kubelka-Munk Turbid Media Theory for Artist Acrylic Paint,
Mahnaz Mohammadi and R.S. Berns, Summer 2004

A common method for characterizing a colored pigment is making a ramp contain several mixtures of the colored and white pigments. Then, by applying the least squares technique using all the samples, absorption and scattering coefficients can be calculated. Making several samples is time consuming. In this approach, the minimum number of samples for characterizing the pigments using single- and two-constant Kubelka-Munk theory was optimized. They are one and two, respectively. The best sample in using the single-constant theory is a sample with the maximum chroma. A mixture of pigment and white at the maximum chroma and a sample of masstone of the pigment are the perfect combinations for characterizing the pigment using the two-constant theory.
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Comparative study of spectral reflectance estimation based on broad-band Imaging systems,
Francisco H. Imai, Lawrence A. Taplin, and Ellen A. Day, April, 2003

We have been practicing spectral color estimation for museum artwork imaging andspectral estimation. We have had success using both narrow-band imaging based on a liquid crystal tunable filter (LCTF) and various broad-band imaging approaches using the same monochromatic digital camera system. Details about our spectral color imaging system description, imaging procedures and the performance of spectral estimation methods used can be found in our previous technical reports. In previous reports we focused on methods of reconstruction from narrow-band images using LCTF, while we only reported preliminary analyses of reconstruction from wide-band images using six glass filtered images and a red-green-blue filter combined with and without a light-blue Wratten filter. There are practical advantages of using commercially available RGB cameras with this method if such a broad-band image acquisition system has sufficient estimation accuracy. We previously captured two sets of six broad-band images obtained by glass filters mounted in a wheel with glass filters, with and without extra absorption filter. In this report, we expand the analyses of spectral estimation using wide-band images by switching the red filter with a long-red filter in order to test the concept ofusing long-red, green and blue channels of the camera combined with and without lightblue absorption filter. The performance of this new configuration is compared to the imaging using all six filters of the filter wheel, as well as the configuration using six channels derived from red-green-blue filters without and with absorption filter.
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Spectral Sensitivies of the Sinarback 54 Camera
D. Collin Day, February 2003

The Sinarback 54 camera is undergoing evaluation for use in spectral imaging. The CCD used in the Sinarback is the Kodak KAF-22000CE with a resolution of 5440x4880 pixels. This technical report describes the process and equipment used to measure the spectral sensitivity of the camera. These data will be used in future experiments to simulate the performance of spectral imaging systems that include the Sinarback camera.
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Evaluation of Optical Flare and Its Effects On Spectral Estimation Accuracy
D. Collin Day, February 2003

Currently, one of the major goals of the Spectral Color Imaging Laboratory at the Munsell Color Science Laboratory is the creation of a spectral imaging system in order to create accurate image archives and lay the groundwork for methods to create nonmetameric image reproductions. While many aspects of the imaging chain have been accounted for, one aspect that requires further investigation is optical flare. This technical report will focus on image acquisition and the need to reduce flare in order to create a mathematical transform which will accurately convert camera digital counts (input) into estimated values of spectral reflectance (output).
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Imaging at the National Gallery of Art, Washington D.C.
Francisco H. Imai, Lawrence A. Taplin, D. Collin Day, Ellen A. Day, and Roy S. Berns, December, 2002

This report provides the description of a recent fine art spectral imaging session at the National Gallery of Art, Washington D. C. This report also includes subsequent evaluation of the performance of our multi-channel visible-spectral imaging (MVSI) system. The multi-band channels analyzed in this report were obtained using a monochrome CCD and a liquid-crystal tunable filter (LCTF) capturing 31 narrow-band channels. The results showed the effectiveness of our designed spectral imaging when used at a museum environment to capture spectral imaging of fine art paintings. Furthermore, we also verified the dependence of the performance on the selection of the characterization target. Various combinations of imaged targets were used to generate the transformation. Among our characterization target combinations, the one that includes GretagMacbeth ColorChecker DC combined with a target of blue pigments was selected considering its impact on spectral estimation performance in reconstructing painting pigments (Gamblin target). This result points directions to a design of a universal target for painting spectral imaging and estimation.
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Image Appearance Modeling and High-Dynamic-Range Image Rendering,
Mark D. Fairchild, Garrett M. Johnson, Jiangtao Kuang, Hiroshi Yamaguchi, May, 2004

Recently, the field of color appearance modeling has been extended further into the spatial and temporal domains through efforts known as image appearance modeling. Image appearance models have applications in rendering and visualization of image data, cross-media image and video reproduction, and image quality specification. This paper provides an overview of one such model, iCAM, illustrates several examples of its application, and reviews a psychophysical experiment aimed at evaluating iCAM, and other algorithms for tone mapping of high-dynamic-range (HDR) images.
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Comparision of the accuracy of various transformations from multi-band Images to reflectancespectra
Francisco H. Imai, Lawrence A. Taplin and Ellen A. Day, Summer 2002

This report provides a comparative study of the spectral and colorimetric accuracy ofvarious transformations from multi-band digital signals to spectral reflectance. The multibandchannels were obtained by multi-channel visible-spectral imaging (MVSI) using a monochrome CCD and two different filtering systems. In the first system we used aliquid-crystal tunable filter (LCTF) capturing 31 narrow-band channels. We also used afilter wheel with a set of 6 glass filters imaging with and without an extra Wratten absorption filter giving a total of 12 channels. Four different mathematical methods were tested to derive reflectance spectra from digital signals: pseudo-inverse, eigenvector analysis, modified-discrete sine transformation (MDST), and non-negative least squares (NNLS). We also considered two different approaches to sampling the digital signals; in one approach we averaged the digital counts.
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Preliminary Experiment for Spectral Reflectance Estimation of Human Iris using a Digital Camera
Francisco H. Imai, June 2002

This technical report summarizes the concept, experiment and results ofspectral reflectance estimation of human iris using a trichromatic digital camera
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Colorimetric Characterization of a Computer-Controlled (SGI) CRT Display
Ellen A. Day, April 2002

ASilicon Graphics CRT monitor was characterized so that multispectral images could be accurately displayed in future research. After several preliminary sets of measurements, an optimal monitor set-up was established. A “contrast” setting of 100% and a “brightness” setting of 20% were used. Three analytical models were evaluated, along with corrections for flare. As expected, the GOG and GOGO models performed much better than the simple gamma model, however, all were acceptable. The GOG model was inverted and chosen to display multispectral images in future research. ΔE*94 was chosen to evaluate all three models. The GOG model resulted in an average ΔE*94 of 0.5 for both the ramp and validation data used in this characterization.
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Characterization of a Roper Scientific Quantix monochrome camera
 Ellen A. Day, Francisco H. Imai, Lawrence A. Taplin and Shuxue Quan, March 2002

A Quantix monochrome camera with a Kodak KAF6303 CCD 2-D array was characterized so that it could be used as a component of a multi-channel visible spectrum imaging system. The results of these experiments were compared to the Certificate of Performance provided by the CCD manufacturer, Roper Scientific. It was found that this particular CCD compares well to the specifications on the Certificate. The spectral sensitive resulting from these experiments will be used for all computations simulations in future research.
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Simulation of spectral estimation of an oil-paint target under different illuminants
Francisco H. Imai, January 2002

This report describes the performance of spectral estimation by computer simulation of 68 oil paints using a transformation matrix from digital counts to reflectance factor derived using eigenvectors derived from an GretagMacbeth ColorChecker color rendition chart in order to evaluate the appropriateness of available illuminants in multi-channel visible spectrum imaging. The wavelength range from 380 to 730 nm was sampled in intervals of 5 nm
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Spectral and Metameric Color Imaging
Mark D. Fairchild, Mitchell R. Rosen, and Garrett M. Johnson(s), August 2001

Spectral imaging has become a topic of growing interest in color-reproduction, remote-sensing, medical-imaging,and other systems. These increased research efforts are likely to propagate into other applicationareas such as computer vision and pattern recognition. This paper defines, compares, and contrasts spectral imaging and more typical metameric imaging which integrates spectral regions. The history of spectral and metameric imaging is reviewed. A public-domain research tool, Spectralizer, for spectral image manipulation, reproduction, and visualization is described. In addition, the advantages of spectral imaging over metameric imaging for object detection applications is demonstrated through simulations created using public domain spectral rendering software and real imaged objects. Finally, all of these pieces are put together in a discussion of system design issues for spectral and metameric systems. It is hoped that these freely-available research tools and systems concepts can be brought to bear on novel imaging problems by researchers in a variety of fields.
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Spectral reproduction from scene to hardcopy
Francisco H. Imai, October 2000

Part I: Multi-spectral acquisition and spectral estimation using a Trichromatic Digital Camera System associated with absorption filters
This report summarizes an experiment performed to evaluate the accuracy of the new multi-spectral acquisition system based on a priori spectral analysis followed by wide-band capture combining trichromatic camera and absorption filters. This report will be focused on the multi-spectral capture and spectral estimation based on a new set of complex image representing a painting and a series of color patches.
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Part II: Multi-spectral acquisition and spectral estimation using a Trichromatic Digital Camera System associated with absorption filters: New results
This report summarizes an experiment performed to evaluate the accuracy of the new multi-spectral acquisition system based on a priori spectral analysis followed by wide-band capture combining trichromatic camera and absorption filters. This report will be focused on the multi-spectral capture and spectral estimation based on a new set of complex image representing a painting and a series of printed color patches with a better distribution in color space.
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Evaluation and Correlation of Color Discrimination Abilities
Sun Ju Park, Scot R. Fernandez, and Lawrence Taplin, June 2000

This study had two parts first evaluating the variability of color discrimination determined by the Colorcurve HVC Color Vision Skill test within a population of "normal" observers and a colorimetric evaluation of the ColorCurve Scoring. For the first evaluation, more than normal variance was found on the red and yellow rows of color. No statistical mean difference was found between any of the observer characteristics noted, such as age, gender, experience, or visionability (corrected/uncorrected). Finally, this evaluation compared the results of two different color discrimination tests; the first population used the Colorcurve HVC Color Vision Skill test and thesecond population used the Farnsworth-Munsell 100 Hue test. The results found no statistical correlations between the two test methods. The second evaluation is discussed in the last part of the appendix, but the understanding is that scoring does not necessarily equate colorimetrically.
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The Science of Digitizing Two-Dimensional Works of Art for Color-Accurate Image Archives - Concepts Through Practice
Roy S. Berns, May 2000

A review of the human visual system, the CIE L*, a*, b* color space and its use in evaluating color-image quality, and digital image capture is presented, the goal of which is to provide background information for imaging professionals involved in creating digital-image databases for museums, archives, and libraries. Following this review, an analysis was performed to determine the effects of bit depth, dynamic range, gamma correction, and color correction on the ability to estimate colorimetric data from R, G, B digital images with a minimum of error. The proper use of gray scale and color targets was also considered. Recommendations are presented for the direct digital image capture of two-dimensional works of art. Finally, a brief look into the future using spectral-imaging techniques is given.
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Direct Digital Imaging of Vincent van Gogh's Self-Portrait - A Personal View
Roy S. Berns, May 2000

The ability to accurately record the color of a painting within an American museum is explored. Limitations in imaging techniques and hardware are current barriers to high quality. Interestingly, simple color-management techniques provide large improvement. Perhaps the greatest advantage is a decrease in visual adjustment. A review is presented of the author's experiences in trying to digitally record the color of Vincent van Gogh's Self-Portrait.
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Colorimetric Characterization of Three Computer Displays (LCD and CRT)
Jason E. Gibson and Mark D. Fairchild, January 2000

The colorimetric characterization of two flat-panel LCD displays, an SGI 1600SW and an IBMprototype, was evaluated and compared to that of a flat-screen CRT display, the Sony GDM-F500.The results showed that both the SGI and the Sony displays could be characterized using thetraditional gain-offset-gamma (GOG) model. Some improvement for the SGI display was gained byusing three 1D LUTs in place of the gamma correction step. The prototype IBM display howeverexhibited a significant failure of additivity and could not be characterized as well as the otherdisplays at this time.
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Multi-spectral Image Acquisition and Spectral Reconstruction using a Trichromatic DigitalCamera System associated with absorption filters
Francisco H. Imai, August 1998

These reports in 8 parts presents the systems, samples, methods used formulti-spectral acquisition and spectral reflectance estimation usingfiltered tricromatic camera systems, as well as discussions about theresults, comparison of methods.This report summarizes researches performed to evaluate the feasibility of using the IBM PRO\3000Digital Camera System associated with Kodak Wratten filters to reconstruct the spectral reflectances ofartwork images and analyzes the performance and discuss possible enhancements.
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Colorimetric Characterization of the Apple Studio Display (Flat Panel LCD)
Mark D. Fairchild and David R. Wyble, July 1998

The colorimetric characterization of a flat-panel LCD monitor, the Apple Studio Display, using traditional CRT characterization techniques was evaluated. Theresults showed that the display performed up to the manufacturer's specificationsin terms of luminance and contrast. However, the traditional CRT gain-offset-gamma(GOG) model for characterization was inadequate and a model with one-dimensional lookup tables followed by a 3x3 matrix was developed. The LUT model performed excellently with average CIE94 color differences between measured and predicted colors of approximately 1.0.
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Report of European Tour
Francisco H. Imai, May 1998

This is a trip report highlighting Francisco's visits to several German and Swiss industrial and academic laboratories.
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The Spectral Modeling of Large-Format Ink-Jet Printers
Roy S. Berns, Animesh Bose, Di-Yuan Tzeng, December 1996

A one-year research and development program was undertaken to colorimetrically characterize large-format ink-jet printers manufactured by Hewlett Packard. Most of the research was performed using the HP650C. Near the end of the project, an HP755CM was used to exemplify the techniques developed on the HP650C. Prints were produced using the 'scatter' mode halftoning algorithm on uncoated ink-jet paper. This report details techniques to modeling the spectral properties of these printers using these halftone algorithms. The principles described herein can be applied to any color imaging process.
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