> 
>         I've been trying to implement something like that as a post_process
> effect, but I can't find an acceptable transfer function. Right now I
> have either an exponential whith no possiblity to change parameter and a
> very small compression range or a rational function whose parameters are
> changeable but whose compression range can't be small (and I haven't had
> time to test it yet anyway...). Any idea what function I could use?

I was going to try these KODAK TRI-X Pan Film / TX Characteristic Curves:
http://www.kodak.co.uk/cluster/global/en/professional/support/techPubs/f9/f9.shtml#10

Density=-log10(intensity)

Then I found something better:
news://news.povray.org/39C95AEC.20DB166A%40kivisalo.net
news://news.povray.org/39C53158.15D04745%40kivisalo.net


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Kari Kivisalo                                  http://www.kivisalo.net

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