Luminance measurement model for high-dynamic-range imaging systems

The measurements of high-contrast scenes, where there are very different levels of luminance simultaneously, is necessary for a growing number of applications in lighting. For evaluating this kind of scene, high-dynamic-range (HDR) measurements with imaging systems are required. A methodology must be established and verified to provide traceable HDR luminance measurements. A measurement model for these measurements is proposed and described, which allows traceability of HDR luminance measurements with imaging systems. This model includes the variables that need to be considered to properly evaluate the uncertainty of the measurement. The uncertainty is derived analytically from the measurement model for luminance measured at individual pixels, and the propagation of this uncertainty is considered when the average luminance across several pixels needs to be measured, including the correlations of the errors at different pixels and luminous sources in the scene. This analytical approach to the evaluation of uncertainty is important for understanding the impact of the different sources of uncertainties. The Monte Carlo approach, which is simpler and easier to implement, is also presented and discussed.