  Image signal processing (ISP) is crucial for camera imaging, and neural
networks (NN) solutions are extensively deployed for daytime scenes. The lack
of sufficient nighttime image dataset and insights on nighttime illumination
characteristics poses a great challenge for high-quality rendering using
existing NN ISPs. To tackle it, we first built a high-resolution nighttime
RAW-RGB (NR2R) dataset with white balance and tone mapping annotated by expert
professionals. Meanwhile, to best capture the characteristics of nighttime
illumination light sources, we develop the CBUnet, a two-stage NN ISP to
cascade the compensation of color and brightness attributes. Experiments show
that our method has better visual quality compared to traditional ISP pipeline,
and is ranked at the second place in the NTIRE 2022 Night Photography Rendering
Challenge for two tracks by respective People's and Professional Photographer's
choices. The code and relevant materials are avaiable on our website:
https://njuvision.github.io/CBUnet.
