QMC | External Illumination only, big GI Portals

GI Bounces: 3, GI-Gamma 2.2, Geometry AA
Scenario: External Illumination only, big GI Portals

click pic to enlarge

So with the insane amount of 4096 samples per shadingpoint (which is every pixel in QMC, that's why it's called brute force method) this scene looks almost perfect, a little bit of grain is still noticeable especially in darker areas. Why don't we get an even noise distribution throughout the whole picture? That is because of the GI gamma of 2.2. If you use a Gamma of 1 you'll get an evenly  distributed noise but the light decay wouldn't look as realistic. Best thing would be to adapt a linear workflow but that is another huge topic. If you're interested check out http://cgpov.com/?p=103 and http://www.thirdpartyplugins.com/degamma/DeGammaDoc.pdf . For now just be aware that raising the GI gamma will give you more grain in darker areas, so you should definetely testrender those spots!
But back to sampling:
How will 4096 samples do in other scenarios, will that be a universal valid samplecount for an almost grainfree render? We're about to find out in the following examples....