An illumination assembly includes a light-emitting element that emits light over a light-source numerical aperture and an elongated light-guiding element including opposed incident and emission ends between which ends light propagates by total internal reflection. The light-guiding element includes along a portion of its length a numerical-aperture alteration taper having opposed small and large ends exhibiting, respectively, a small-end numerical aperture and a large-end numerical aperture lower in magnitude than the small-end numerical aperture. The alteration taper is oriented such that the small end is more proximate the incident end than the large end. The incident end is in light-collecting proximity and alignment with the light-emitting element such that light emitted from the light-emitting element over the small-end numerical aperture and received into the small end of the alteration taper is emitted from the emission end of the light-guiding element at an emission numerical aperture lower in magnitude than the small-end numerical aperture.