This is most likely a "mirror ghost flare" effect
that occurs when a bright light is
The flare is generally due to the presence of a protective filter in the camera, after the lens. The flare is a mirror ghost of the original bright
object, with the image center serving as a point of symmetry (or point reflection
All dimensions are, most of the time, perfectly preserved, which suggests that reflections at planar surfaces are responsible. However, this is not
exactly the case in your photo, as:
1- the line (green) that join the light source and its ghost image do not exactly pass through the photo center and
2- the length of the two segments from the center to the light source firstly and to the ghost image secondly aren't the same.
This is due to the fact that the filter on this camera is not plane, but curved.
Let's see how it works on a planar filter with the figure below:
Black arrows indicate the light rays of a distant bright light source that form a regular image point on the film (1). Values for the reflectance of
undeveloped photographic film vary from 15% to 40% [see sources 1,2], which makes the film a much stronger reflector than any optical component in the
So, a significant percentage of the light is reflected off the film, partly specular and partly diffuse. (For convenience, we will consider that paths
of the reflected light are the same and thus are already drawn for the incident light).
Thus, the blue arrows
indicate light reflected from the film. This light encounters the filter, which specularly reflects a
small fraction (red arrows
). The red rays are parallel and consequently focused onto a point on the film. (2)
The virtual source of the mirror point is traced by the dashed black lines. Note that the blue rays reflected by the film seem odd from the viewpoint
of specular reflection; they merely illustrate the fact that all light rays that originate from a single point on the film, and which are collected by
the lens, emerge parallel at the filter.
edit on 24-6-2012 by elevenaugust because: (no reason given)