Maps of in units of θ_E for f₂ = 0.4 and γ_p = 0.1. Top panel: we use the same color-coding as in Fig. 3 to explicitly show that |Δ α (θ)| < 5 × 10⁻³ θ_E over a region of the lens plane does not guarantee the image offsets |Δθ| to be smallerthan 5 × 10⁻³ θ_E over the same region. Bottom panel: we adjust the color-coding to bring out regions where the image offsets |Δ θ | are the largest, namely the critical curves.