VisionBlue has rendered two of the same images, with just slightly modified settings.
The perceived overall quality is close to identical, while he was able to save ~47% render time.
All details in the images below:
ummm you know those are both the same file ?
(I assume the second one is testrender2.jpg)
and for the record, I prefer the second one for some reason
AA really hammers you, apparently. The quality isn't so noticable for this (low/medium-sized render), but AA might have a much larger impact on large renders. Still, this is really useful to know - thanks!
I don't think it's the AA, but more to do with the Detail and GI settings. AA is just a 2D post process and is quite cheap compared to the other settings in terms of cpu power.
I'd hazard a guess that the biggest increase in time will be got from GI. I have mine on 1 for the renders I've done so far. 2, and the render time almost doubles. 3 and I have to cancel at bed time ;)
GI does have a significant impact. AA should be relatively less so but still has a definitely effect. It's good to see concrete example that "higher is not always better". In fact I prefer image #2 as well, with the lower settings. I do find it odd that he used such a strange and precise decimal value for detail in the 1st though. It would have been a better test if detail had been the same and only AA and GI changed.