  This paper reviews the first challenge on high-dynamic range (HDR) imaging
that was part of the New Trends in Image Restoration and Enhancement (NTIRE)
workshop, held in conjunction with CVPR 2021. This manuscript focuses on the
newly introduced dataset, the proposed methods and their results. The challenge
aims at estimating a HDR image from one or multiple respective low-dynamic
range (LDR) observations, which might suffer from under- or over-exposed
regions and different sources of noise. The challenge is composed by two
tracks: In Track 1 only a single LDR image is provided as input, whereas in
Track 2 three differently-exposed LDR images with inter-frame motion are
available. In both tracks, the ultimate goal is to achieve the best objective
HDR reconstruction in terms of PSNR with respect to a ground-truth image,
evaluated both directly and with a canonical tonemapping operation.
