Photometric calibration of high dynamic range cameras

The current trends in computer graphics focus on acquiring, processing and reproducing real world scenes, often with a quite high dynamic range (HDR). Many algorithms require such HDR image or video data as an input and the increasing availability of HDR sensors provides a natural source of them. But at the same time the diversity of HDR sensor technology leads to a strong need for photometric calibration of such HDR camera systems in order to retain the fidelity of the final result. We present a calibration approach based on an earlier HDR recovery algorithm for standard low dynamic range (LDR) cameras. We focus here on the specific challenges posed by cameras with a dynamic range of more than six orders of magnitude such as complex camera response curves or selection of appropriate calibration targets. We perform an absolute calibration of two HDR and one LDR camera systems to allow for recovery of real-world luminance values. To validate our approach, we compare these luminance values to measurements performed with a luminance meter for grayscale patches covering a dynamic range of six orders of magnitude. The achieved accuracy of the photometric calibration is sufficient for many measurement and image-based acquisition applications.