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Publications (11)2.95 Total impact

  • Robert C Carter · Louis D Silverstein
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    ABSTRACT: We generalize, to images with continuously varying colors, our previously published model for comparing color differences of spatially discrete visual fields (icons, symbols) of disparate sizes. Our model is structural, including scattering of light by the intraocular media, followed by sparse retinal cone cell sampling of each physiological color primary. We use our model to show that small subtense of less than half a degree drastically reduces the number of discriminable colors available within a color gamut. The proposed generalization predicts and explains appearance of color fields having a wide range of subtenses (from 1/8 deg to 44 deg in examples given).
    No preview · Article · Jul 2012 · Journal of the Optical Society of America A
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    ABSTRACT: The use of color LCDs in medical imaging is growing as more clinical specialties use digital images as a resource in diagnosis and treatment decisions. Telemedicine applications such as telepathology, teledermatology, and teleophthalmology rely heavily on color images. However, standard methods for calibrating, characterizing, and profiling color displays do not exist, resulting in inconsistent presentation. To address this, we developed a calibration, characterization, and profiling protocol for color-critical medical imaging applications. Physical characterization of displays calibrated with and without the protocol revealed high color reproduction accuracy with the protocol. The present study assessed the impact of this protocol on observer performance. A set of 250 breast biopsy virtual slide regions of interest (half malignant, half benign) were shown to six pathologists, once using the calibration protocol and once using the same display in its "native" off-the-shelf uncalibrated state. Diagnostic accuracy and time to render a decision were measured. In terms of ROC performance, Az (area under the curve) calibrated = 0.8570 and Az uncalibrated = 0.8488. No statistically significant difference (p = 0.4112) was observed. In terms of interpretation speed, mean calibrated = 4.895 s; mean uncalibrated = 6.304 s which is statistically significant (p = 0.0460). Early results suggest a slight advantage diagnostically for a properly calibrated and color-managed display and a significant potential advantage in terms of improved workflow. Future work should be conducted using different types of color images that may be more dependent on accurate color rendering and a wider range of LCDs with varying characteristics.
    No preview · Article · May 2012 · Journal of Digital Imaging
  • Louis D. Silverstein · Syed F. Hashmi · Karl Lang · Elizabeth A. Krupinski
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    ABSTRACT: — A methodology and associated software modules for calibration, characterization, and profiling of color LCDs for color-critical applications in medical imaging is described. Supporting analyses reveal very high color-reproduction accuracy as determined by CIE DE2000 color differences for 21 0 test colors uniformly distributed in CIE Lab color space. The impact of the LCD tone-reproduction curve on color-reproduction accuracy is compared for two tone-reproduction curves of special interest in medical imaging: the DICOM gray-scale standard display function and the CIE L* standard lightness function. The initial results from a psychophysical investigation of the diagnostic performance of trained pathologists viewing “virtual” breast biopsy slides are reported and the diagnostic performance achieved with calibrated, color-managed LCDs with uncalibrated LCDs without the benefits of color management is compared.
    No preview · Article · Jan 2012
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    ABSTRACT: A methodology and associated software modules for calibration, characterization and profiling of color LCDs for color-critical applications such as medical imaging is described. Supporting analyses reveal very high color reproduction accuracy as determined by CIE DE2000 color differences for 210 test colors uniformly distributed in CIE Lab color space.
    Preview · Article · Jun 2011
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    ABSTRACT: Our laboratory has investigated the efficacy of a suite of color calibration and monitor profiling packages which employ a variety of color measurement sensors. Each of the methods computes gamma correction tables for the red, green and blue color channels of a monitor that attempt to: a) match a desired luminance range and tone reproduction curve; and b) maintain a target neutral point across the range of grey values. All of the methods examined here produce International Color Consortium (ICC) profiles that describe the color rendering capabilities of the monitor after calibration. Color profiles incorporate a transfer matrix that establishes the relationship between RGB driving levels and the International Commission on Illumination (CIE) XYZ (tristimulus) values of the resulting on-screen color; the matrix is developed by displaying color patches of known RGB values on the monitor and measuring the tristimulus values with a sensor. The number and chromatic distribution of color patches varies across methods and is usually not under user control. In this work we examine the effect of employing differing calibration and profiling methods on rendition of color images. A series of color patches encoded in sRGB color space were presented on the monitor using color-management software that utilized the ICC profile produced by each method. The patches were displayed on the calibrated monitor and measured with a Minolta CS200 colorimeter. Differences in intended and achieved luminance and chromaticity were computed using the CIE DE2000 color-difference metric, in which a value of ▵E = 1 is generally considered to be approximately one just noticeable difference (JND) in color. We observed between one and 17 JND's for individual colors, depending on calibration method and target.
    No preview · Article · Mar 2010 · Proceedings of SPIE - The International Society for Optical Engineering
  • Robert C. Carter · Louis D. Silverstein
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    ABSTRACT: — A long-standing problem in color science is the accurate estimation of color differences for visual targets of small angular subtense. For instance, “What is the magnitude of a 0.5° color difference that will be as discriminable as a given 2° color difference?” Or, “What is the reduced angular subtense (or increased distance) at which two visual fields of given colors will become appreciably less discriminable than they were at larger subtense (or smaller distance)?” Past attempts at solving this problem have been specific to a particular color-difference equation and, as such, the work lost relevance as improved color-difference formulae were developed. This article proposes a structural model based upon the response of retinal cone cells to small-subtense symbol images scattered by the ocular media. The method is demonstrated to be applicable without alteration to very different contemporary color-difference equations, to be practical with a wide range of surround intensities, and to have high correlation with human search performance involving small color symbols on an electronic information display.
    No preview · Article · Jan 2010
  • Edward F. Kelley · Karl Lang · Louis D. Silverstein · Michael H. Brill
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    ABSTRACT: A standard methodology exists for estimating the flux from front projection displays by sampling the projected illuminance of a white source signal. With the advent and use of white projection primaries, a dramatic increase in flux can be achieved over the combination of red, green, and blue primaries alone. However, saturated-color areas in an image are constrained to low flux levels relative to the display maximum and further undergo a perceptual compression in relative lightness when a white primary is used. As a result, bright saturated colors cannot be rendered accurately and the appearance of full-color imagery is distorted. Due to these problems, the display of color-accurate imagery does not generally use the white primary. We verify a measurement method that fills the need for providing an equivalent flux measurement that will better describe the performance of all RGB and RGBW projectors when they render full-color imagery.
    No preview · Conference Paper · Jan 2009
  • Edward F. Kelley · Karl Lang · Louis D. Silverstein · Michael H. Brill
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    ABSTRACT: A standard methodology exists for estimating the flux from front projection displays by sampling the projected illuminance of a white source signal. with the advent and use of white projection primaries, a dramatic increase in flux can be achieved over the combination of red, green, and blue primaries alone. However, saturated-color areas in an image are constrained to low flux levels relative to the display maximum and further undergo a perceptual compression in relative lightness when a white primary is used. As a result, bright saturated colors cannot be rendered accurately and the appearance of full-color imagery is distorted. Due to these problems, the display of color-accurate imagery does not generally use the white primary. We verify a measurement method that fills the need for providing an equivalent flux measurement that will better describe the performance of all RGB and RGBW projectors when they render full-color imagery.
    No preview · Article · Jan 2009 · SID Symposium Digest of Technical Papers
  • Louis D. Silverstein
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    ABSTRACT: This chapter discusses the principles of human vision that are used to design image capture and display devices. The chapter provides an overview of the properties of human vision that are essential in designing color-imaging technologies. It describes the application of these and related principles along with the specific technologies. Digital cameras and scanners are reviewed in this chapter. The chapter discusses displays with a particular emphasis on cathode ray tube (CRT) and liquid crystal display (LCD) technologies. The main focus is on the fundamental principles of color imaging technology that must be addressed in the design of capture and display technology. Quantitative methods useful for certain specific devices are described, and it is expected that these methods will be useful for future generations of display and capture technologies as well.
    No preview · Article · Jul 2003
  • Michael H. Brill · Louis D. Silverstein
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    ABSTRACT: This paper provides a methodology which bridges the gap between a simple color-difference metric and a full spatio-chromatic vision model to predict color differences. Because luminance and chromatic visual channels differ greatly in their spatial sensitivities, more than a single number is needed for specific applications—e.g., performance of softcopy displays. On the other hand, a full vision model implies dependence on the displayed images as well as on the display device, and may be impractical to implement. The compromise proposed here is to adopt in certain cases two color-difference metrics, one for luminance and the other for chrominance. Because chromatic coordinates are not luminance-independent in uniform color spaces such as CIELAB, the endpoints of the color difference are made isoluminous prior to transformation to a uniform-color space.
    No preview · Article · Jan 2002 · SID Symposium Digest of Technical Papers
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    Edward F. Kelley · Karl Lang · Louis D. Silverstein

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