Material emission strength

[baka]

I have a scene illuminated by 3 planes placed 50 cm away from a lightbox and I'm trying to adjust the exposure. The material has blackbody for base emission with gain value 1. The image is extremely overexposed, the only way to get it under control is to set camera exposure to 1/1000 or EV adjust to -10.
Why is the emission so strong?

[CTZn]

If no emission scale is specified, a gain of 1 is extremely high indeed for a blackody, specifically. You should adapt the emission value instead of twisting the exposure, in this case you want to reduce the blackbody's gain.

[baka]

How come the lights in the material preview scene have the same gain but the image isn't overexposed?

[galinette]

How come the lights in the material preview scene have the same gain but the image isn't overexposed?

They have emission scales defined. The emission scale overrides the material gain on a per-object basis, to match the requested lumen value. This means, when the emission scale is used, that blackbody gain has no effect.

Using emission scale is quite exporter-dependent, which one do you use?

Etienne

[baka]

I figured as much, I'm exporting with indigo for max and there's all sorts of things missing one of them being emission scale.It wouldn't have been too annoying but indigo render doesn't have that setting either which led me to wonder what was wrong.

[CTZn]

It wouldn't have been too annoying but indigo render doesn't have that setting either which led me to wonder what was wrong.

Emission scale applies per Object as you will find them in the Scene lister. This systems adapts emission powers to square surfaces, sort of I think.

[galinette]

It wouldn't have been too annoying but indigo render doesn't have that setting either which led me to wonder what was wrong.

Emission scale applies per Object as you will find them in the Scene lister. This systems adapts emission powers to square surfaces, sort of I think.

To any surface. It computes the material base candela.sr output, then the object area, whose product give the base lumen output. It then scales the emission power accordingly to match the specified lumen output

[baka]

That did the trick, thanks for the help guys.