QMC | Internal illumination only (object Illumination)

GI Bounces: 3, GI-Gamma 2.2, Geometry AA
Scenario: Internal illumination only (object illum.) large lights

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Actually this one already looks quite nice with 1024 samples, 4096 is a bit overkill, except (again due to the gamma2.2 setting) the darker areas.

Scenario: Internal illumination only (object illum.) small lights  

 

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So yes, same rule applies for internal lights concerning the samplecount:
You need higher settings if you have smaller but (to compensate the overall brightness) stronger lightsources.
Consider this if you render out for example an archvis with day- and nightshot.