The gain for Bidirectional integrator was something I added due to an empirical observation that the scene exposure value was completely different with that integrator, but all the others were consistent. I didn't understand it at the time and still do not - I simply noted that if I wanted to be able to switch integrators and keep lighting exposure levels the same, I had to do that.

The 1000 * BBLuxMat.BBLuxMatDIRatio was there because glowing objects and light sources have to agree on power. The ratio of direct to indirect light (DIRatio) was something I was exploring at the time, also empirically, since the documentation of LuxRender says absolutely nothing about these things. The factor of 1000 was just so I did not have to type tiny fractions like .000674 (or maybe it was the other way, to avoid having to type giant numbers) into the DIRatio. I never did finalize all those things.

I have no doubt that your 25000 is also one of these mysterious magnitude anomalies for which we will likely never get an explanation. I was just asking if the 60,000 x factor was what you expected SG. And it was. So good.

Now back to the question - why is Robyn's infinite light so weak as to effectively be disabled?

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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)