4 February 2013 Acquisition of multi-spectral flash image using optimization method via weight map
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To acquire images in low-light environments, it is usually necessary to adopt long exposure times or to resort to flashes. Flashes, however, often induce color distortion, cause the red-eye effect and can be disturbing to the subjects. On the other hand, long-exposure shots are susceptible to subject-motion, as well as motion-blur due to camera shake when performed with a hand-held camera. A recently introduced technique to overcome the limitations of the traditional lowlight photography is the use of the multi-spectral flash. Multi-spectral flash images are a combination of UV/IR and visible spectrum information. The general idea is to retrieve the details from the UV/IR spectrum and the color from the visible spectrum. Multi-spectral flash images, however, are themselves subject to color distortion and noise. In this work, a method of computing multi-spectral flash images so as to reduce the noise and to improve the color accuracy is presented. The proposed method is a previously seen optimization method, improved by introducing a weight map used to discriminate the uniform regions from the detail regions. The optimization target function takes into account the output likelihood with respect to the ambient light image, the sparsity of image gradients, and the spectral constraints for the IR-red and UV-blue channels. The performance of the proposed method was objectively evaluated using longexposure shots as references.
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Bong-Seok Choi, Bong-Seok Choi, Dae-Chul Kim, Dae-Chul Kim, Oh-Seol Kwon, Oh-Seol Kwon, Yeong-Ho Ha, Yeong-Ho Ha, "Acquisition of multi-spectral flash image using optimization method via weight map", Proc. SPIE 8652, Color Imaging XVIII: Displaying, Processing, Hardcopy, and Applications, 86520U (4 February 2013); doi: 10.1117/12.2005466; https://doi.org/10.1117/12.2005466

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