Top panel (and top-left insert): Hα integrated fluxes measured by GHASP compared with Hα integrated fluxes from Boselli et al. (2015); the solid red line represents the OLS bisector linear regression on the data from which results our calibration; the insert at the top-left shows the same calibration plot but using a linear scale. Bottom panel: normalised residual values, where f_NB are fluxes from Boselli et al. (2015) and f_FP are GHASP calibrated fluxes.