I don't know how they stack up statistically, but there is FAR more anecdotal evidence around about sample variation in Sigma lenses than about any other brand, Tamron would be next worst. BTW, what does that have to do with 4/3 sensors being "bad"? They're not, they just have a roughly 50% higher pixel density than comparable resolution APS sensors - which lessens the size of the photosensitive parts of the pixel, making them somewhat less light sensitive.Originally Posted by Don Kondra