Adaptive Tone-Mapping Transfer Functions for High Dynamic Range Video Cameras

For real-time imaging with digital video cameras, good tonal rendition of video is important to ensure high visual comfort for the user. Except local contrast improvements, high dynamic range (HDR) scenes require adaptive gradation correction (tone-mapping curve) that should enable good visualization of details at lower brightness. We discuss how to construct and control optimal tone mapping curves, which enhance visibility of image details in the dark regions while not excessively compressing the image in the bright image parts. The result of this method is a 21 dB expansion of the dynamic range. The new algorithm was successfully evaluated in HW and is suited for any video system performing HDR video compression.