wow.  i didn't need all that, but thank you.  all you had to say was a) there is a hue and saturation shift, and b) no, the lights' output needs to be linear because (if i'm interpretting what you said properly, please correct me if i'm wrong) you need linear info for the interaction with nodes on the surfaces.   makes perfect sense.  the part i was missing was the information about how lights work internally, which is seriously interesting and i thank you for sharing it, but it would have made sense just as a black box of equations.

that said, you're basically making an argument for the simplified correction not working, either.  because if it won't work to just do it at the end for GC or sRGB correct, why would it work to do the same thing with your new equation?  i mean, if i'm not misunderstanding the equation, translating it to a GC equivalent would just be changing the value of the exponent.  i interpretted your statements about the new equation as not affecting hue and saturation was at least a fair approximation of anti-correcting first, if not more correct.  am i misunderstanding?

just given how similar the curves are, i'm not sure i see why it would be so different for (higher values) to use the new equation vs. either sRGB or GC.

as for iterative rendering, what you seem to be saying, and please correct me if i'm wrong, is that non-uniform IBL doesn't affect the a flat surface realistically.  which affects just about every use of IBL, not just iterative rendering techniques.  i mean, great, if you're just using entirely photo backgrounds.  but not great if you need to light anything with a flat ground and non-uniform light.  which is a whole lot of uses of IBL.  i can't speak for anyone else, but that sounds like a bigger problem than the iterative issue.

i would say that if you think light correction is such a big deal, you should be much more vocal about it.  i would guess that almost no one following your advice is correcting the lights.  i've never seen anyone mention it, at least.  and, if i'm understanding properly, you're talking about just anti-correcting the lights.  that is, you need the output of the light's base node to be linear, not corrected.  it seems like a really drastic change to the lighting.   you don't really work artistically, so that shift wouldn't be a big deal to you.  but as an artist who needs to eyeball to acheive what i'm visualizing, i'm going to have to think hard about what this means in terms of how i should execute lighting.  that is, how what i see in the material room and maybe use in parameters matches what i envision.  it  might mean i shouldn't change much.  but i'm not so sure of that.

oh!  just to ask because i'm at work and don't have Matmatic documentation here, are lights' base node elements controllable in Matmatic?  could you show a quick example of how to make a simple light material?

oh, and a more general question: can we ever distribute materials based on what we're learning here (and in other threads)?  i mean, proper accreditation goes without saying.  i'm really less worried about commercial than free, but it would probably be good to clarify in general.  it's just kind of weird to be caught between thinking, "wow, every freebie and product should have these features," and, "i can't distribute this because it's not really mine."