Different noise from different light sources

[maru]

I suppose it's not a bug, but I'd like to hear some explanations why this happens. From left: sphere with CoronaMtl, sphere with CoronaLightMtl, spherical CoronaLight. LSM was set to 1.

[Ondra]

yep, spherical CoronaLight is better, that is expected behavior, since it is analytical sphere, not polygonal

[racoonart]

Left is coronaMtl with selfillumination? If yes then it's simply GI noise (means: rays are not shot to the lightsource but everywhere and don't hit the sphere all the time -> more noise)
Middle: more noise because your mesh light is sampled per polygon (like many little triangular lights)
Right: perfect mathematical sphere, so it can be sampled a lot better

[maru]

Understood.