This work provides a novel glass-to-glass metric of local contrast, useful in the context of image quality evaluation of HDR content. This metric, called Local-Contrast Gain (LCG), uses the opto-optical transfer function (OOTF) of the imaging system and its first derivative to compute the incremental ratio between contrast in the scene and contrast on the display. In order to be perceptually meaningful, we chose Weber’s definition of contrast. In order know the OOTF in analytical form and to make the measurement robust to the uncertainty of measurements of the ground truth, we rely on a model that we propose and that expands upon our previously published work. We provide experimental validation of our metric on a variety of target charts, both reflective and transmissive, both in isolation and within complex setups spanning more than six EVs.