strange behaviour, may be only radiance or ma cosx?

unfortunately I tried bubble and sphere, same thing.
The real difference is when I use glow with the 4th number to act like a
light source.
In that case it acts like a light and it illuminates! the sphere/bubble
glows on the inner surface... (while light does nothing...)
So why only light?
Any ideas appreciate!
thanks a lot

BTW I was used to employ the inner part of a sphere in a script of mine to
create a polar distribution of a light source (basically an illuminance
image of a dome with a light source in the middle and a known radii)... may
be stretching radiance capabilities...
Now it's no more working :frowning:

PS settings are default, without ambient bouncing.


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