For those who don't read c.g.r.r., Matt Pharr posted a link to an article
on tone mapping using the zone system.
http://www.cs.utah.edu/~reinhard/cdrom/
http://www.cs.utah.edu/~reinhard/cdrom/tonemap.pdf
Could be of interest for POV-Ray, but certainly for images created with
POV-Ray.
Ingo
