The Experts below are selected from a list of 9732 Experts worldwide ranked by ideXlab platform
Leonard G.c. Hamey - One of the best experts on this subject based on the ideXlab platform.
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DICTA - Simultaneous Estimation of Camera Response Function, Target Reflectance and Irradiance Values
Digital Image Computing: Techniques and Applications (DICTA'05), 2005Co-Authors: Leonard G.c. HameyAbstract:Video cameras may be used for radiometric Measurement in machine vision applications including Colour Measurement and shape from shading. These techniques assume that the camera provides a linear Measurement of light intensity. Even when the video gamma factor is disabled, video camera response is still often nonlinear and varies from one camera to another. We describe a method of measuring a cameras radiometric response function using unknown but stable reflectance targets and illumination. The technique does not require sophisticated equipment or precise Measurement or control of physical properties. The technique simultaneously estimates the camera's radiometric response, the relative reflectance values of reflectance targets and the relative illumination levels of multiple light sources. The technique has been practically applied for Colour Measurement applications with an experimentally verified accuracy of 0.3%.
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Simultaneous estimation of camera response function, target reflectance and irradiance values
Proceedings of the Digital Imaging Computing: Techniques and Applications DICTA 2005, 2005Co-Authors: Leonard G.c. HameyAbstract:Video cameras may be used for radiometric Measurement in machine vision applications including Colour Measurement and shape from shading. These techniques assume that the camera provides a linear Measurement of light intensity. Even when the video gamma factor is disabled, video camera response is still often nonlinear and varies from one camera to another. We describe a method of measuring a camera's radiometric response function using unknown but stable reflectance targets and illumination. The technique does not require sophisticated equipment or precise Measurement or control of physical properties. The technique simultaneously estimates the camera's radiometric response, the relative reflectance values of reflectance targets and the relative illumination levels of multiple light sources. The technique has been practically applied for Colour Measurement applications with an experimentally verified accuracy of 0.3%. © 2005 IEEE.
Swati Baindurhudson - One of the best experts on this subject based on the ideXlab platform.
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a comparison of hair Colour Measurement by digital image analysis with reflective spectrophotometry
Forensic Science International, 2009Co-Authors: Michelle R Vaughn, Roland A H Van Oorschot, Swati BaindurhudsonAbstract:Abstract While reflective spectrophotometry is an established method for measuring macroscopic hair Colour, it can be cumbersome to use on a large number of individuals and not all reflective spectrophotometry instruments are easily portable. This study investigates the use of digital photographs to measure hair Colour and compares its use to reflective spectrophotometry. An understanding of the accuracy of Colour determination by these methods is of relevance when undertaking specific investigations, such as those on the genetics of hair Colour. Measurements of hair Colour may also be of assistance in cases where a photograph is the only evidence of hair Colour available (e.g. surveillance). Using the CIE L * a * b * Colour space, the hair Colour of 134 individuals of European ancestry was measured by both reflective spectrophotometry and by digital image analysis (in V++). A moderate correlation was found along all three Colour axes, with Pearson correlation coefficients of 0.625, 0.593 and 0.513 for L * , a * and b * respectively ( p -values = 0.000), with means being significantly overestimated by digital image analysis for all three Colour components (by an average of 33.42, 3.38 and 8.00 for L * , a * and b * respectively). When using digital image data to group individuals into clusters previously determined by reflective spectrophotometric analysis using a discriminant analysis, individuals were classified into the correct clusters 85.8% of the time when there were two clusters. The percentage of cases correctly classified decreases as the number of clusters increases. It is concluded that, although more convenient, hair Colour Measurement from digital images has limited use in situations requiring accurate and consistent Measurements.
J. C. Coops - One of the best experts on this subject based on the ideXlab platform.
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Influence of window size in small-window Colour Measurement, particularly of teeth
Physics in Medicine and Biology, 1994Co-Authors: René A. Bolt, J. J. Ten Bosch, J. C. CoopsAbstract:Tooth Colour is often measured with a small window for illumination and Measurement. This causes edge loss of the light, resulting in systematic errors in Colour coordinates. This paper gives a quantification of the edge losses, and explains their cause. We measured reflectance spectra for 27 Formalin fixated extracted incisors using a small-window reflectance spectrophotometer equipped with external diaphragms of 3, 4, and 5 mm diameter, and using a spectroradiometer. We calculated the Colour coordinates L*a*b* from these spectra. Finally, 16 randomly chosen teeth were illuminated with a pencil beam (lambda = 543 nm, and lambda = 633 nm) while the emerging light was measured as a function of distance from the illuminated spot using a CCD detector. These data were used to calculate small-window edge losses, and thus to predict the small-window reflectance factors relative to spectroradiometrically determined reflectance, at both 543 nm and 633 nm. In all instruments the same spot on the tooth was illuminated and measured, and the teeth were always wet. Colour coordinates for the small-window Colour Measurements deviate significantly from those determined using the spectroradiometer. These deviations can be explained from the wavelength-dependant edge loss that arises in small-window Colour Measurement.
Michelle R Vaughn - One of the best experts on this subject based on the ideXlab platform.
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a comparison of hair Colour Measurement by digital image analysis with reflective spectrophotometry
Forensic Science International, 2009Co-Authors: Michelle R Vaughn, Roland A H Van Oorschot, Swati BaindurhudsonAbstract:Abstract While reflective spectrophotometry is an established method for measuring macroscopic hair Colour, it can be cumbersome to use on a large number of individuals and not all reflective spectrophotometry instruments are easily portable. This study investigates the use of digital photographs to measure hair Colour and compares its use to reflective spectrophotometry. An understanding of the accuracy of Colour determination by these methods is of relevance when undertaking specific investigations, such as those on the genetics of hair Colour. Measurements of hair Colour may also be of assistance in cases where a photograph is the only evidence of hair Colour available (e.g. surveillance). Using the CIE L * a * b * Colour space, the hair Colour of 134 individuals of European ancestry was measured by both reflective spectrophotometry and by digital image analysis (in V++). A moderate correlation was found along all three Colour axes, with Pearson correlation coefficients of 0.625, 0.593 and 0.513 for L * , a * and b * respectively ( p -values = 0.000), with means being significantly overestimated by digital image analysis for all three Colour components (by an average of 33.42, 3.38 and 8.00 for L * , a * and b * respectively). When using digital image data to group individuals into clusters previously determined by reflective spectrophotometric analysis using a discriminant analysis, individuals were classified into the correct clusters 85.8% of the time when there were two clusters. The percentage of cases correctly classified decreases as the number of clusters increases. It is concluded that, although more convenient, hair Colour Measurement from digital images has limited use in situations requiring accurate and consistent Measurements.
Gerhard Grull - One of the best experts on this subject based on the ideXlab platform.
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Prediction of wood surface discoloration for applications in the field of architecture
Wood Science and Technology, 2018Co-Authors: Boris Forsthuber, Gerhard GrullAbstract:Semitransparently coated wooden building elements such as facades and windows undergo disColouration during exposure to sunlight, depending on the environmental conditions and protective properties of the coatings. The present paper aims at the development of numerical prediction models of photo-induced disColouration as a basis for texture synthesis for CAD applications. Wood samples of European larch and Norway spruce were coated with several (semi-) transparent coatings with varying Colours and dry film thicknesses and exposed to Xenon arc light with outdoor cut-off filter to simulate outdoor irradiation conditions. Colour prediction models were developed from the obtained Colour Measurement data in the CIE XYZ Colour space, since the progression of corresponding values showed a monotonous curve characteristic of each coating system. A novel Colour Measurement procedure was developed to estimate the Colour of early- and latewood in the annual rings of wood. This method made it possible to generate Colour-consistent textures for use in rendering software, as demonstrated on two examples.