Streetlight reflections in a night photograph from Groix

Summary

A witness submitted a photograph taken in Groix showing three unexplained red spots. Optical analysis revealed that each spot was an internal lens reflection of a streetlight. When lines are drawn between each streetlight and its corresponding red spot, all three segments converge at a single central point matching the optical centre of the lens. The brightness of each spot varies with the distance of its source streetlight in the frame.

Although internal lens reflections are a common phenomenon, this image is considered a textbook example. The symmetrical arrangement of the three streetlights around the optical axis produces a particularly clean result, making it an excellent illustration of how such artefacts are generated.