Estimate of the r factor corresponding to the actual value of σ_G we need to use in the testing environment to both account for the noise correlation and match the noise properties of the E images with the D images. The blue and the black dotted curves show the linear fits to the quantities defined in Eqs. (7) and (8), which were then used in test Ic. Their intersection defines the estimated value for r^true and the corresponding σ_G (red dot).