Alain <kua### [at] videotronca> wrote:

>
> When using a mirrored sphere, there is a blind cone right behind it: The
> area of the view hiden from the camera by the sphere itself.
> There is also a loss of definition near the edge.

> remove the camera, to get a full spherical covering.

Thanks, Alain; the idea is finally beginning to make sense to me.

I always like to have a theoretical understanding of how things work; but I have
not yet come across a physical description of how light rays behave as they
strike the circular edge of a mirrored sphere. So here is my own 'thought
experiment': The circular 'edge' can be thought of as an infinite number of tiny
'flat' mirrors, each one aligned *almost* parallel to the camera's line of
sight. Since "angle of incidence = angle of reflection", the reflected light
rays (from the surrounding environment) do indeed come from areas 'behind' the
sphere! :-) (Except for the small missing cone, as you mentioned.)

I tried this experiment by eye, with a flat mirror-- and it works (of course!)
Duh!  It all seems so obvious now.

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