Exposure versus contrast enhancement in low-light 4k videos

Abstract

The terms “exposure enhancement” and “contrast enhancement” are usually used interchangeably for image enhancement in low-light acquisitions. This paper argues that the two processes are anything but alike. While exposure can be inferred from low frequency or background of an image, contrast by definition refers to the ratio of the foreground with the background. We break down the Lambertian illumination model in a multiresolution framework and show how foreground and background at different levels contribute to contrast and exposure enhancement. Following this, a fast multiresolution low-light enhancement scheme is proposed that achieves a frame rate of 19.62 frames per second on standard quad core processor without employing any graphical processing unit. Experiments reveal that the proposed scheme is not only fast, it also achieves state-of-the-art performance in terms of subjective and objective assessment.