Fusion of Bracketing Pictures

Abstract

When taking pictures in a night scene with artificial lighting, a very common situation, for most cameras the light coming from the scene is not enough and we are posed with the following problem: we can use the flash which yields a bright, sharp image but with colors quite different from the ones present in the real scene, or we can either increase the exposure setting so as to let the camera absorb more light, or just keep the normal (short) exposure setting and take a dark picture. If we discard the flash as an option and use instead the exposure bracketing feature available in most photo cameras, we obtain a series of pictures taken in rapid succession with different exposure times, with the implicit idea that the user picks from this set the better looking image. But it's a quite common situation that none of these images is good enough: in general, good color information is retained from longer exposure settings while sharp details are obtained from the shorter ones. In this work we propose a technique for automatically recombining a bracketed pair of images into a single picture that reflects the optimal properties of each one. The proposed technique uses stereo matching to extract the optimal color information from the overexposed image and Non-local means denoising to suppress noise while retaining sharp details in the luminance of the underexposed image.