[JJ_SO]

Another thing to remember is that full frame lenses are usually pretty rubbish wide open towards the edges.

 

Which goes not for dedicated APS-C lenses?  ^_^

 

Besides, I don't would use the word "rubbish" for the fast Sigma Arts, but have to admit that I hardly use the corners when shooting wide open, as there's no AF-point on my D810 close to the edges. I also don't shoot landscapes wide open, so I could at least use LiveView to focus.

 

DoF at f/1.4 is ridiculously thin, so some of the "poor edges" might come from focus problems as well. And the weight of those lenses is simply a punishment for the owner.