General relativistic photon paths around a Schwarzschild black hole. Light follows null geodesics — curved by spacetime curvature. At r = 3M, the photon sphere allows circular orbits. Below r = 2M lies the event horizon — no return.
Critical impact parameter b_c = 3√3 M ≈ 5.196M. Below b_c: captured. Above: deflected. Near b_c: extreme lensing.