By the way, you used the word "tone" (tone down or up). In discussion of HDR, the subject of "tone mapping" is different from simply multiplying with a factor.

The idea of tone mapping is to transform the image so that you compress the range back into an LDR image, so that nothing is brighter than 1.0. In other words, the range 0 to infinity is mapped to the range 0 to 1.

There are many different math formulas that accomplish this. One of them is the exponential formula used in Poser 8. Most can be made in HSV versions where an attempt is made only to alter the luminance, while preserving the saturation and value. In other words, instead of doing the mapping in RGB color space, we do it in HSV color space. That is the difference between HSV Exponential and simple Exponential tone mapping.

As I said, the exponential type is supported in P8, but we can do it with nodes in any version of Poser that supports HDR (P7 and up).

Another tone mapping formula that I came up with is x/(x+1). (And other similar variants using different constants.) It produces different looking results from the exponential formula. There are good and bad things about both.

If you desire, I can show how to do tone mappings.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)