[thxbb12]

The sigma 17-70 is less complex, as zooming may be done on both sides of the aperture stop (non-constant aperture), is larger, and has more spherical aberration.  It does have significantly worse build, at least externally, as well. 

 

To be clear, I do think the 16-70 is a poor lens, but I also think Imatest is overstating the weakness of its performance as well.

 

Personally, I couldn't care less about the complexity of a lens. In fact, given two lenses, a simple and a complex one, featuring the same IQ, I'd take the simpler one any day.

 

Also: why is that that a f2.8-4.0 lens is easier to design than a constant f4 lens? It doesn't seem to make much sense to me given the 2.8-4.0 will be brighter at best and the same at worst.