[JJ_SO]

I don't want to talk down the Canon. It's just not only the corners...

 

And that weather sealing is a term Nikon fanboys often pull out of the backyard when they run out of reasons to decide for a Nikon instead another's brand lens. However, my answer to them (can't talk about Canon) remains the same: "please guys, do post a link where I can read Nikon's statement and specification of "weather sealing", because otherwise it's a little pointless". Nikon themselves doesn't call their lenses "weather-sealed" or "weather-proof", last time I checked.

 

It's always some kind of weather, isn't it? So, against which kind of weather in particular the sealing is actively protecting? Which kind of picture can I take in a pouring European rain, snow-storm - in massive conditions I don't have to take photographs and am hardly in the mood going out in a thunderstorm and take a flash or a falling branch on my head. I don't consider myself as hardcore, all-shitty-weather-compatible photographer. I am a whimp  :unsure: why not admit it? 

 

I think, zooms are a different story, but I bet the Sigma would not give up earlier in bad weather than my old Nikon. I woudn't take any of them on a dive.

[Rover]

It is weather sealed, and it may focus faster and more accurately (Canon USM). That the Sigma does better in corners wide open is not that important, as usually the subject is not in the corners. So, I would not think about it too much, unless you run into something in particular.

No, not yet. I'm not shooting it wide open a lot - it has saved me with the 1.4 aperture on a couple of occasions where the light was truly horrible, but I haven't done any scientific tests so far. I'm usually using it at least 1 1/2 stops from wide open anyway, often more. But I know what to pull out when the light gets really dim...

[JJ_SO]

"it may focus faster and more accurately" - any source for this statement of belief?  Or just the usual Canon fanboy stuff? Besides, neither Canon, Nikon or Sigma have problems focusing fast enough. And if it comes to accuracy, the lens' part of Sigma is pretty well adjustable to the camera part of the AF process. Contrary to the big boys where you need to decide if you go for close distance accuracy or distant subjects.

 

Actually, I just shot a couple of wide open stuff in daylight where the subjects were as well in center as also at the borders - to me this situation is not that rare not to think about. But depending how quick I need to be to get the shot, it really doesn't matter if the edges are blurred because a lack of DoF or inaccurate focusing or blurred edges from the lens' side. However, I eventually get some sharp corners insteaf of being completely at the "sharp corners are impossible" side