[Rover]

FWIW ... after having used the lens out there over the weekend - the experience tells me - once again - that DSLRs and EOS cameras in particular just can't focus accurately with ultra-wides. The margin of error is HUGE and, of course, it was especially bad with this large aperture Sigma lens.

Things are fine with close-up but for middle-ground scenes (2-3m) things are going down the hill rapidly. The camera is just focusing too far to the rear.

This is reassuring... For me. Ever since I've got the Sigma 14/2.8 I've been struggling with its sometimes odd focus behavior on medium and longer distances. I used to think that it was either a flawed sample, a flawed design per we, or a flawed (aka dumb) operator behind the camera - but if it's none of the above (just the nature of the game), I can stop chiding myself and/or trying to get rid of the lens. Which, I might add, despite being from a very old generation of Sigmas, worked well otherwise on a range of bodies, from 40D up to 1D X.