Upload & Sell: On
As far as telephotos go, I think my CZ Sonnar 100/3.5 has slight concave curvature of the plane of focus, at infinity focus distance. IOW, the edges can be in focus while the centre hasn't quite made it to sharp focus. That's the way it behaves at f/3.5 on the generic CY to EOS adapter that I'm currently using. At f/8, it's sharp everywhere, even behind me.
I'l check it again when my Leitax kit arrives.
As far as I can remember, most of the wide angle lenses I've owned that have noticeable curvature of the plane of focus are convex, but as Micahel says, any particular lens can be very different.