Map of |Δθ(β)|_max in units of θ_E for f₂ = 0.4 and γ_p = 0.1 (see Eq. (42)). The inner (resp. outer) green line represents the tangential (resp. radial) caustic curve. The two hatched regions (B₁ and B₂) delimited by blue curves demarcate parts of the source plane where |Δθ(β)|_max ≤ 5 × 10⁻³ θ_E. The region B₁ lies inside the tangential caustic curve while B₂ lies outside. The inset highlight the region around the position β = 0.