Schematic illustration of the polarization from photospheric emission. Left: illustration of the photons (black lines) scattering from the jet (purple) toward the observer. The green dotted line represents the observers viewing axis. The photons scattering toward the observer in the photosphere (top layer of the jet), close to the line of sight will have a scattering angle θ ≈ 180°, whereas θ goes closer to 90° when moving away from the viewing axis. As a result, the polarization increases with the polarization angle into the drawn plane. Middle: the jet (purple) seen from the top along with the observed area (gray, with size 1/Γ) centered around the viewing axis (green). With the full observed area contained in the jet, the various polarized areas will cancel out one another, resulting in no net polarization. Right: same as the middle panel in a situation in which the observer area not fully contained in the jet, allowing for a net observed polarization, with a polarization angle perpendicular to the off-axis viewing angle (θ_v = ι).