Pixel-to-pixel comparison of the blue area (NOAA AR 12960) in Fig. 1 of the azimuth of SDO/HMI and SO/PHI-FDT. Panel A shows the original azimuth of SDO/HMI, ϕ, and the panel D displays the one inverted with the VFISV code using the Stokes maps convolved with the SO/PHI-FDT PSF, ϕ′. In both panels the azimuths are compared pixel-to-pixel against the SO/PHI-FDT azimuth. The roll angles have been corrected to establish a common origin for azimuth measurements in the SO/PHI-FDT and SDO/HMI datasets. The blue lines show linear fits. Points where |ϕ_HMI − ϕ_FDT|> 90° are excluded due to the intrinsic azimuthal ambiguity. The fits and Pearson correlation coefficients are given in the insets. Panels B and E show the same area as the SO/PHI-FDT azimuth without and with the polarimetric mask, respectively. Panels C and F show the SDO/HMI azimuth, ϕ and ϕ′, respectively. The total number of pixels compared are 1784 for panel A and 3417 for panel D.