The geometry of black hole spacetimes can be probed with exquisite precision in the gravitational-wave window, and possibly also in the optical regime. We study the accretion of bright spots-objects which emit strongly in the optical or in gravitational waves-by nonspinning black holes. As the object approaches the event horizon, the emitted radiation to far-away distances is dominated by photons or gravitons orbiting the light ring, causing the total luminosity to decrease exponentially as L-o similar to e(-t/(3 root 3M)). Late-time radiation is blueshifted, due to its having been emitted during the infall, trapped at the light ring and subsequently reemitted. These universal properties are a clear signature of the existence of light rings in the spacetime, and not particularly sensitive to near horizon details.