Sighting in Groix, May 19, 2008

A witness sent GEIPAN a photograph showing red spots. Analysis of the image showed that the red dots were reflections of street lamps inside the camera lens.

When each street lamp was joined to its corresponding red dot, the three lines crossed at a single point, the "mirror" point of the effect. That point sat exactly at the centre of the photograph, which is the focal point of the lens. The strength of each red spot depended on how far the lamp appeared from the centre of the image, so their brightness varied.

GEIPAN noted that this effect is fairly common, but that this photograph was a genuine "textbook case", probably because the three street lamps were grouped around the optical centre of the lens. The case was classified A (identified): red spots on a photograph.