Camera Dynamic Range Measurement: The Role of Lenses and Target Spatial Distribution

High dynamic range (HDR) is still considered a technological issue related to sensors’ dynamic or effectiveness of multiple exposures. To this aim, test charts have been devised to supposedly measure this sensor/camera limit. This study aims to show how these test charts do not measure the actual camera dynamic range (DR) since this depends on the spatial arrangement and size of test chart luminance values and on the chosen lens. In this work, we have reported test measures that show how camera DR acquisition depends on the scene spatial distribution of luminance and the glare caused by lens optical scattering. We have reported measures that underline how glare (or flare) represents the main DR limitation in the acquisition phase of systems with lenses, and we assess its influence on the DR of the acquired image. The experiments performed in this work were done in a controlled environment, and pointwise instrumental measures were compared with camera acquisitions using different lenses and setups. The tests here presented report a reduction in the acquired DR of 48% on average, varying across different test setups, with four different lens types and five step chart layers forming varying DRs. Here, we propose a more realistic point of view in DR assessment since the effect of glare and spatial distribution of luminances in the acquired DR is massive, systematic, and unavoidable.