In my scene I have a light fixture with three bulbs, each of which is surrounded by a glass globe. The material on the bulb is an emission shader with a strength of 1.0, so they’re not letting off much light at all. The brightness itself is coming from three point lights positioned just behind each bulb, outside the glass globes.
The weird part is the reflection on the shower glass to the right of the image. You can see each bulb, and each glass globe, but it also looks like you can see each point light behind each bulb (the white discs of light between the fixture and the wall). Why would the point lights themselves be invisible where the camera is looking directly at them, but appear as round balls of light in the reflection?