When taking pictures in a dark scene with artificial lighting, the ambient light is not sufficient for most cameras to obtain both accurate color and detail information. The exposure bracketing feature usually available in many camera models enables the user to obtain a series of pictures taken in rapid succession with different exposure times; the implicit idea is that the user picks the best image from this set. But it is often the case that none of these images is good enough: in general, good brightness and color information are retained from longer exposure settings while sharp details are obtained from shorter ones. In this work we propose a variational method for automatically combining an exposure bracketed pair of images into a single picture that reflects the desired properties of each one. We introduce an energy functional consisting of two terms, one measuring the difference in edge information with the short exposure image and the other measuring the local color difference with a warped version of the long exposure image. The method is able to handle camera and subject motion as well as noise, and results compare favorably with the state of the art.

The first authoracknowledges partial support by AACC project, referenceTIN2011-15954-E, and by the ERC Starting Grant “ImageProcessing for Enhanced Cinematography.” The second authoris funded in part by NSF-DMS #0915219.