The Experts below are selected from a list of 14007 Experts worldwide ranked by ideXlab platform
Peter Hanselaer - One of the best experts on this subject based on the ideXlab platform.
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Chromaticity of unique white in illumination mode
Optics Express, 2015Co-Authors: Kevin A G Smet, Geert Deconinck, Peter HanselaerAbstract:The Chromaticity of unique white viewed in illumination mode and under dark adapted conditions was investigated for 3 luminance levels (200, 1000 and 2000 cd/m2) using a unique white setting method. Unique white was found to encompass a rather large region in color space located slightly below the blackbody locus and centered around a CCT of 6600 K. Luminance level was found to have no significant effect on the mean unique white Chromaticity. The high and low end points of the CIE class A and B white regions respectively under- and overestimate the Chromaticity region perceived as white. Agreement along the Duv direction was quite good. However, another Duv related limit associated with white lighting (|Duv|≤5.4e-3) was found to be on the small side, especially for Chromaticity values below the blackbody locus. The results for unique white viewed in illumination mode were compared to those reported for object mode presentation. Overall they were very comparable, although a statistical analysis does show a (just) significant effect of stimulus presentation mode for high (il)luminance levels. However, no such effect could be established at the individual observer level. Therefore, it was concluded that unique white Chromaticity is essentially the same for both illumination and object mode stimulus presentation, at least under dark adapted viewing conditions.
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Chromaticity of unique white in object mode
Optics Express, 2014Co-Authors: Kevin A G Smet, Geert Deconinck, Peter HanselaerAbstract:The Chromaticity of unique white viewed in object mode and under dark adapted conditions was investigated for 3 luminance levels (200, 1000 and 2000 cd/m2) using two experimental methods: unique white setting and rating. The results of the two methods were found to agree well. Both showed quite large observer variation and an apparent shift of the average unique white (across observers) towards colder correlated color temperatures as the stimulus luminance was dropped from 2000 cd/m2 to 200 cd/m2, although no such trend was observable at the individual observer level. Unique white was shown to encompass a region in color space, mostly located below the blackbody locus at around 6000 K. The low and high color temperature ends of the CIE class A and B white regions tend to respectively over- and slightly underestimate the size of the Chromaticity area perceived as white by the dark adapted average observer. However, the agreement along a direction approximately perpendicular to the blackbody locus was quite good. Finally, the unique white ratings were modeled by a bivariate Gaussian function, resulting in a simple empirical metric to predict the degree of neutrality of any object stimulus viewed under dark adapted conditions.
Philippe C Cattin - One of the best experts on this subject based on the ideXlab platform.
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quantification of contrast recognizability in sequential epiretinal membrane removal and internal limiting membrane peeling in trypan blue assisted macular surgery
Retina-the Journal of Retinal and Vitreous Diseases, 2013Co-Authors: Paul B Henrich, Siegfried G Priglinger, Christos Haritoglou, Rupert W Strauss, Ricarda G Schumann, Ulrike Schneider, Tatjana Josifova, Philippe C CattinAbstract:Purpose: To evaluate the selectivity and strength of intraoperative trypan blue staining during removal of epiretinal membranes (ERMs) and the internal limiting membrane. Methods: Based on intraoperative videos, 51 consecutive chromovitrectomies in 51 patients with macular holes, macular pucker, vitreomacular traction syndromes, or persistent macular edema were retrospectively studied. Fifteen subjects underwent trypan blue, 14 indocyanine green, and 22 brilliant blue G chromovitrectomy. The main outcome measure was the color contrast between stained internal limiting membrane or ERM and the underlying unstained tissue by means of objective, quantitative, semiautomated Chromaticity difference measurements. Results: Trypan blue stains both ERM and the internal limiting membrane (average Chromaticity scores 8.51 and 7.09, respectively; P = 0.48). Internal limiting membrane Chromaticity scores were similar for trypan blue (7.09) and brilliant blue G (6.81; P = 0.71) but clearly higher for indocyanine green (15.81; P = 2.45 +/- 10(-5)). Conclusion: Under the premises of our study, trypan blue stains both ERM and the internal limiting membrane. Trypan blue's staining capacity of the internal limiting membrane is similar to that of brilliant blue G but significantly inferior compared with indocyanine green. Trypan blue, thus, represents a useful vital dye for chromovitrectomy, particularly in the presence of ERM, where it allows a sequential approach. RETINA 33:818-824, 2013
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contrast recognizability during brilliant blue g and heavier than water brilliant blue g assisted chromovitrectomy a quantitative analysis
Acta Ophthalmologica, 2013Co-Authors: Paul B Henrich, Christophe Valmaggia, Corina Lang, Siegfried G Priglinger, Christos Haritoglou, Rupert W Strauss, Philippe C CattinAbstract:. Purpose: To evaluate the potential of heavier-than-water brilliant blue G (BBG-D20) to stain the internal limiting membrane (ILM) during chromovitrectomy. Methods: In a nonrandomized, prospective, clinical multicentre study, 71 consecutive chromovitrectomy interventions in 71 patients were analysed. During routine 23-gauge vitrectomy, conventional 0.25 mg/ml BBG was employed in 21 and 0.25 mg/ml BBG-D20 in 50 patients. All interventions were videotaped. Post-operatively, video frames were viewed and dye performance assessed subjectively and objectively. Main outcome measure was the Chromaticity difference between the stained ILM and the unstained underlying retina, measured by means of an objective and quantitative analysis method to describe colour contrast strengths as they are perceived by the human eye. Results: Removal of the ILM was possible in all interventions without additional vital dyes. BBG-D20 readily sank to the retinal surface, while conventional BBG tended to swirl up throughout the vitreous cavity. Conventional BBG was removed either with active suction or with a flute needle. Brilliant blue G-D20 needed to be whirled up from the retinal surface with a flute needle before aspiration. Objective Chromaticity measurements yielded a mean Chromaticity score of 7.98 for BBG-D20 and 6.51 for BBG (p = 0.09). Conclusions: Brilliant blue G-D20 readily sinks to the retinal surface after injection and can be conveniently removed with a flute needle or active suction during chromovitrectomy. Based on the premises of the Chromaticity measurements in this study, BBG’s ILM staining capacity was not significantly improved through the recent revision its preparation, although a tendency towards slightly improved contrasts between the ILM and the underlying retina was observed.
Kevin A G Smet - One of the best experts on this subject based on the ideXlab platform.
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Chromaticity of unique white in illumination mode
Optics Express, 2015Co-Authors: Kevin A G Smet, Geert Deconinck, Peter HanselaerAbstract:The Chromaticity of unique white viewed in illumination mode and under dark adapted conditions was investigated for 3 luminance levels (200, 1000 and 2000 cd/m2) using a unique white setting method. Unique white was found to encompass a rather large region in color space located slightly below the blackbody locus and centered around a CCT of 6600 K. Luminance level was found to have no significant effect on the mean unique white Chromaticity. The high and low end points of the CIE class A and B white regions respectively under- and overestimate the Chromaticity region perceived as white. Agreement along the Duv direction was quite good. However, another Duv related limit associated with white lighting (|Duv|≤5.4e-3) was found to be on the small side, especially for Chromaticity values below the blackbody locus. The results for unique white viewed in illumination mode were compared to those reported for object mode presentation. Overall they were very comparable, although a statistical analysis does show a (just) significant effect of stimulus presentation mode for high (il)luminance levels. However, no such effect could be established at the individual observer level. Therefore, it was concluded that unique white Chromaticity is essentially the same for both illumination and object mode stimulus presentation, at least under dark adapted viewing conditions.
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Chromaticity of unique white in object mode
Optics Express, 2014Co-Authors: Kevin A G Smet, Geert Deconinck, Peter HanselaerAbstract:The Chromaticity of unique white viewed in object mode and under dark adapted conditions was investigated for 3 luminance levels (200, 1000 and 2000 cd/m2) using two experimental methods: unique white setting and rating. The results of the two methods were found to agree well. Both showed quite large observer variation and an apparent shift of the average unique white (across observers) towards colder correlated color temperatures as the stimulus luminance was dropped from 2000 cd/m2 to 200 cd/m2, although no such trend was observable at the individual observer level. Unique white was shown to encompass a region in color space, mostly located below the blackbody locus at around 6000 K. The low and high color temperature ends of the CIE class A and B white regions tend to respectively over- and slightly underestimate the size of the Chromaticity area perceived as white by the dark adapted average observer. However, the agreement along a direction approximately perpendicular to the blackbody locus was quite good. Finally, the unique white ratings were modeled by a bivariate Gaussian function, resulting in a simple empirical metric to predict the degree of neutrality of any object stimulus viewed under dark adapted conditions.
Maricor Soriano - One of the best experts on this subject based on the ideXlab platform.
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comparison of skin color detection and tracking methods under varying illumination
Journal of Electronic Imaging, 2005Co-Authors: Birgitta J Martinkauppi, Maricor Soriano, Matti PietikainenAbstract:When skin areas such as faces and hands are imaged under natural environments their color appearance is frequently af- fected by variations in illumination intensity and Chromaticity. In color-based skin tracking and detection, changing intensity is often dismissed either with the use of normalized, intensity-invariant color coordinates or by additionally modeling possible skin intensities. Chromaticity variations are rarely considered, although they are common in practice. In most approaches considering Chromaticity, the experiments are done with a small or undefined variation range. It is difficult to compare different approaches and assess their appli- cability range for this reason. To improve the situation, we evaluate the performance of four state-of-the-art methods under drastic but practically common illumination changes. The effect of illumination Chromaticity for skin is clearly defined, and based on it we draw conclusion about the performance of these approaches. © 2005
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detection of skin color under changing illumination a comparative study
International Conference on Image Analysis and Processing, 2003Co-Authors: Birgitta Martinkauppi, Maricor Soriano, Matti PietikainenAbstract:Faces and hands recorded under natural environments are frequently subject to illumination variations which affect their color appearance. This is a problem when the color cue is used to detect skin candidates at pixel level. Traditionally, color constancy has been suggested for correction, but after a lot of effort no good solution suitable for machine vision has emerged. However, many approaches have been proposed for general skin detection, but they are typically tested under mild changes in illumination Chromaticity or do not define the variation range. This makes it difficult to evaluate their applicability for objects under varying illumination. The paper compares four state-of-the-art skin detection schemes under realistic conditions with drastic Chromaticity change.
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adaptive skin color modeling using the skin locus for selecting training pixels
Pattern Recognition, 2003Co-Authors: Maricor Soriano, Birgitta Martinkauppi, Sami Huovinen, Mika H LaaksonenAbstract:Techniques for color-based tracking of faces or hands often assume a static skin model yet skin color, as measured by a camera, can change when lighting changes. Therefore, for robust skin pixel detection, an adaptive skin color model must be employed. We demonstrate a Chromaticity-based constraint to select training pixels in a scene for updating a dynamic skin color model under changing illumination conditions. The method makes use of the ‘skin locus’ of a camera, that is, the area in Chromaticity space where skin Chromaticity under various lighting and camera calibration conditions is observed. Skin color models derived from the technique are compared with that derived by a common spatial constraint and is shown to be more consistent with manually extracted ground truth skin model per frame even as localization errors increase. The technique is applied to color-based face tracking in indoor and outdoor videos and is shown to succeed more often than other color model adaptation techniques. ? 2002 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.
Paul B Henrich - One of the best experts on this subject based on the ideXlab platform.
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quantification of contrast recognizability in sequential epiretinal membrane removal and internal limiting membrane peeling in trypan blue assisted macular surgery
Retina-the Journal of Retinal and Vitreous Diseases, 2013Co-Authors: Paul B Henrich, Siegfried G Priglinger, Christos Haritoglou, Rupert W Strauss, Ricarda G Schumann, Ulrike Schneider, Tatjana Josifova, Philippe C CattinAbstract:Purpose: To evaluate the selectivity and strength of intraoperative trypan blue staining during removal of epiretinal membranes (ERMs) and the internal limiting membrane. Methods: Based on intraoperative videos, 51 consecutive chromovitrectomies in 51 patients with macular holes, macular pucker, vitreomacular traction syndromes, or persistent macular edema were retrospectively studied. Fifteen subjects underwent trypan blue, 14 indocyanine green, and 22 brilliant blue G chromovitrectomy. The main outcome measure was the color contrast between stained internal limiting membrane or ERM and the underlying unstained tissue by means of objective, quantitative, semiautomated Chromaticity difference measurements. Results: Trypan blue stains both ERM and the internal limiting membrane (average Chromaticity scores 8.51 and 7.09, respectively; P = 0.48). Internal limiting membrane Chromaticity scores were similar for trypan blue (7.09) and brilliant blue G (6.81; P = 0.71) but clearly higher for indocyanine green (15.81; P = 2.45 +/- 10(-5)). Conclusion: Under the premises of our study, trypan blue stains both ERM and the internal limiting membrane. Trypan blue's staining capacity of the internal limiting membrane is similar to that of brilliant blue G but significantly inferior compared with indocyanine green. Trypan blue, thus, represents a useful vital dye for chromovitrectomy, particularly in the presence of ERM, where it allows a sequential approach. RETINA 33:818-824, 2013
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contrast recognizability during brilliant blue g and heavier than water brilliant blue g assisted chromovitrectomy a quantitative analysis
Acta Ophthalmologica, 2013Co-Authors: Paul B Henrich, Christophe Valmaggia, Corina Lang, Siegfried G Priglinger, Christos Haritoglou, Rupert W Strauss, Philippe C CattinAbstract:. Purpose: To evaluate the potential of heavier-than-water brilliant blue G (BBG-D20) to stain the internal limiting membrane (ILM) during chromovitrectomy. Methods: In a nonrandomized, prospective, clinical multicentre study, 71 consecutive chromovitrectomy interventions in 71 patients were analysed. During routine 23-gauge vitrectomy, conventional 0.25 mg/ml BBG was employed in 21 and 0.25 mg/ml BBG-D20 in 50 patients. All interventions were videotaped. Post-operatively, video frames were viewed and dye performance assessed subjectively and objectively. Main outcome measure was the Chromaticity difference between the stained ILM and the unstained underlying retina, measured by means of an objective and quantitative analysis method to describe colour contrast strengths as they are perceived by the human eye. Results: Removal of the ILM was possible in all interventions without additional vital dyes. BBG-D20 readily sank to the retinal surface, while conventional BBG tended to swirl up throughout the vitreous cavity. Conventional BBG was removed either with active suction or with a flute needle. Brilliant blue G-D20 needed to be whirled up from the retinal surface with a flute needle before aspiration. Objective Chromaticity measurements yielded a mean Chromaticity score of 7.98 for BBG-D20 and 6.51 for BBG (p = 0.09). Conclusions: Brilliant blue G-D20 readily sinks to the retinal surface after injection and can be conveniently removed with a flute needle or active suction during chromovitrectomy. Based on the premises of the Chromaticity measurements in this study, BBG’s ILM staining capacity was not significantly improved through the recent revision its preparation, although a tendency towards slightly improved contrasts between the ILM and the underlying retina was observed.