Actually I did mention GC lighting impacts. In a post a week ago: (but of course you can't read every post I make)

Did you know that setting the light color is not the same as setting the light intensity when GC is involved?

With Poser Pro render GC enabled, all material node color parameters, including those on lights, are anti-gamma corrected before being used. This means that your 50% gray was not 50% gray. It was about 22% gray. That was multiplied with the 40% intensity, yielding an effective illumination of 8.7%, not the 20% you thought. So your effective total illumination from 5 lights was 8.7% * 5 = 43.5%, less than half of my single WHITE spotlight at 95%.

In your last post you said 40% * 50% * 50% * 5 = 50%. In that calculation what is the second 50% for? Without GC the calculation would be

Intensity * color * number_of_lights = 40% * 50% * 5 = 100%

With GC the calculation would be:

Intensity * color * number_of_lights = 40% * (50% ^ 2.2) * 5 = 43.5%

For this reason, I never use gray to decrease a light intensity. I always use white, and I use the intensity dial to adjust ... intensity.

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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)