TempRetinex: Retinex-based Unsupervised Enhancement for Low-light Video Under Diverse Lighting Conditions

Abstract: Videos inherently contain rich temporal information that provides complementary cues for low-light enhancement beyond what can be achieved with single images. We propose TempRetinex, a novel unsupervised Retinex-based framework that effectively exploits inter-frame correlations for video enhancement. To address the poor generalization of existing unsupervised methods under varying illumination, we introduce adaptive brightness adjustment (ABA) preprocessing that explicitly aligns lighting distributions across exposures. This significantly improves model robustness to diverse lighting scenarios and eases training optimization, leading to better denoising performance. For enhanced temporal coherence, we propose a multi-scale temporal consistency-aware loss to enforce multiscale similarity between consecutive frames, and an occlusion-aware masking technique to handle complex motions. We further incorporate a reverse inference strategy to refine unconverged frames and a self-ensemble (SE) mechanism to boost the denoising across diverse textures. Experiments demonstrate that TempRetinex achieves state-of-the-art performance in both perceptual quality and temporal consistency, achieving up to a 29.7% PSNR gain over prior methods.