Dynamic range compression preserving local image contrast for digital video camera

This paper presents a novel dynamic range compression method for digital video cameras. The proposed algorithm is designed to preserve a local image contrast based on a luminance ratio of a pixel to its local surround in attention. In general, digital video cameras are required to maintain the shadow to middle range luminance that includes a main object such as a facial area. According to this requirement, most digital video cameras have adopted a knee curve as a dynamic range compression function that strongly compresses only the highlight range over the knee point. But this method has the weakness that severely lowers a highlight contrast. To overcome this weakness, the proposed algorithm automatically and adaptively enhances the local image contrast in the highlight regions. As a result, the highlight area such as blue sky is realistically reproduced without lowering the input luminance in the shadow to middle range.