I believe it reverts to its original, sensitive state. I ain't a chemist though.
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As a chemist, I don't know. I think it is possible but unlikely that a crystal could be "desensitized" in a low photon flux. Someone with more knowledge of solid-state physics might know.
As to the term Schwarzschild effect, my first association wasn't to Schwarzenegger (I read German, when I have to), but I did wonder for a moment about the photographic application of black holes.
-- Ole Tjugen, Luddite Elitist