Simulated Exposure Fusion

Abstract

Simulated Exposure Fusion (SEF) is a single-image contrast enhancement method. It is built upon a high dynamic range imaging technique called Exposure Fusion (EF), introduced in 2007 and widely used since then, which aims at fusing a bracketed exposure sequence into a high quality image. Simulated Exposure Fusion extends the initial method to the case where only one image is available, and delivers an image with enhanced contrast. We propose in this paper an implementation of this method, along with its precise description and analysis. Its results are compared to state-of-the-art enhancement algorithms and appear to be artifact-free, even in extreme enhancement conditions. Furthermore, they inherit from EF's celebrated natural aspect. Source Code The Matlab/Octave source code, the code documentation, and the online demo are accessible at the web page of this article 1. Usage instructions are included in the README.txt file of the archive.

An Analysis and Implementation of the HDR+ Burst Denoising Method

“…• Hdr tone mapping: we use a technique close to the one employed in [9], where two synthetic exposures are created from a single image and combined with exposure fusion [16] (a similar strategy is extended and demonstrated in [12]). From the result of all previous steps (which stems from an underexposed burst), we get a grayscale image by averaging the 3 color channels and then synthesize two exposures: we apply the standard sRGB gamma correction to get a short exposure, and we apply a gain followed by the same gamma correction to synthesize the long exposure.…”

“…In 2018, [9] was completed by a very large dataset captured with several smartphones, simply named the HDR+ dataset 12 . It is comprised of 3640 raw bursts (28461 images total), for a total of 765 GB.…”

“…• Gamma compression: pixel values are shifted from linear to non-linear sRGB space in order to both reduce the required bandwidth and produce a more pleasing and identifiable look, taking advantage of the human visual sensitivity which is also non-linear (for example, humans are more sensitive to brightness differences in darker tones versus brightness differences in brighter tones). The sRGB transfer function is defined by the IEC 61966-2-1 international standard 12 as…”