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27 January 2010 Digital neutral density filter for moving picture cameras
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Proceedings Volume 7533, Computational Imaging VIII; 75330L (2010)
Event: IS&T/SPIE Electronic Imaging, 2010, San Jose, California, United States
Typical image sensors in digital cameras have a fixed sensitivity, and the amount of captured light energy is often controlled by adjusting exposure time and lens aperture. For high end motion imaging these settings are not available as they are used to set motion blur and depth of field, respectively. In many cases a proper exposure is achieved with additional optical filtering, using so called "neutral density" (ND) filters. We propose a digital equivalent of a neutral density filter, which can replace the handling of optical filters for camera systems. It consists of an adjusted sensor readout and in-camera processing of images. Instead of a single long exposure we capture N short exposures. These images are then combined by averaging. The short exposures reduce the sensitivity by a factor of N, while averaging reconstructs motion blur. In addition we also achieve a reduction of both dynamic and fixed pattern noise which leads to an overall increase in dynamic range. The digital ND filter can be used with regular image sensors and does not require hardware modifications.
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Michael Schöberl, Alexander Oberdörster, Siegfried Fößel, Hans Bloss, and André Kaup "Digital neutral density filter for moving picture cameras", Proc. SPIE 7533, Computational Imaging VIII, 75330L (27 January 2010);


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