I'm not going to post any more results from the HSV Exponential unless anyone really wants to see them.

I've just had my D'Oh moment - Exponential tone mapping should really be called RGB Exponential because it's mapping in the RGB color space.  HSV Exponential is mapping in the HSV Color space.  If I had used HSV tuples instead of RGB tuples in my second listing, it would have followed the exact same pattern as the first data set.  (I don't know if I can make IrfanView show HSV instead of RGB, but I'm not going to worry about it now).