Equatorial photon geodesics around Top Panel: a nonrotating Schwarzschild black hole (a/M = 0), Bottom Panel: a maximally rotating Kerr black hole (a/M = 0.998). The black disk represents the event horizon and the gray ring illustrates the ergosphere of the black hole, respectively. Plunging photon geodesics are depicted in blue, while geodesics that escape to infinity are shown in purple.