Map of the per-superpixel conversion gain (e⁻ ADU⁻¹) of a flight H2RG detector from the Euclid mission, measured using the standard mean-variance method. The map reveals two distinct regions, a characteristic feature of many H2RG detectors commonly caused by a lack of epoxy between the ROIC and the sensitive layer. Non-negligible gain variations persist even within a single region.