Panasonic 12-35 @ 12 and 14mm f2.8 how sharp is yours

I went out  and shot brick walls at a range of apertures and focal lengths when mine arrived. I'd say there's some corner softness, but not a great deal and only in the extreme corners at 12mm and 2.8 which disappears at 4.0 or by zooming to around 14-15mm. It is however better at 2.8 and 12mm than my 14-140 at optimum aperture (say 8.0) and 14mm.