I’ve recently seen three Blender add-ons* that try to deal with getting real world lights into Blender, which all came to the same conclusion, that the sun is per default way to dim, and to counteract their brightening of the sun they all change the exposure by roughly 6 stops.
I wanted to ask if someone more knowledgeable with cycles or color management might comment on this and explain a bit on why these add-ons are doing this and why Cycles / Blender isn’t doing it per default.
These addons are trying to achieve physical values in the renderer, meaning they are trying achieve real world sun strength. We actually have Nishita Sky texture in Blender that does this by default, it follows the physical values since it makes the most sense.
As to why other parts of Blender are not doing this, the answer in my understanding is two-fold:
Engines like Cycles uses clamping to bias the render for better performance. This is actually controversial, as people have complained the default indirect clamping of 10 is negatively affecting Nishita sky. I think the default should be changed to 80.
Cycles also samples less of the “dimmer” lights, if you follow the physical emission intensity of a candle, Cycles by default would make the render extremely noisy because it consider the candle to be too dim to contribute to the scene, so it samples less of it. You can lower the Light Threshold setting to weaken this sampling bias.
Most users are not trying to use physically correct lights, and they are not expecting to need to change the exposure slider. Though I tried to tell my local community to use the exposure slider and keep the lights physical, I failed and realized most people just keeps the exposure unchanged and just tweak the light strength to satisfaction. This is just the reality of how most people are using the software. Though the need to use physical lights does exist, it doesn’t cover the majority.
Despite what’s said, I also think this kind of addon should be shipped with the official Blender for the people who need it. But the addon authors need to take the initiative to submit their addon.