Optical effects on HDR calibration via a multiple exposure noise-based workflow

Abstract

High dynamic range (HDR) technology allows more of the lighting in a specific scene to be captured at a set point in time, and thus is capable of delivering an overall view of the scene that more closely correlates with our visual experience in the real world, compared to standard, or low dynamic range (LDR) technology. Although HDR capabilities of single exposure capture systems are improving, the traditional method for creating HDR images still includes combing a number of different exposures, captured with an LDR system, into a single HDR image. Several use cases requiring absolute calibration of the resulting HDR luminance map have been undertaken, but none of these have provided a detailed analysis of the optical effects of glare on the results. We develop a calibrated HDR radiance map, including methodical linearization of captured image data, while characterizing the limitations due to the effects of optical glare. A purposely designed controlled test scene is used to challenge the calibrated reconstruction efforts, including low luminance levels, spatial inclusion of lens vignette over the full imaged area, and optical glare. Results demonstrate that even with careful processing and recombination of the LDR data, radiometric accuracy is limited as a result of glare. The proposed approach performs better than calibration methods in commercially available HDR recombination software.