Taken at 24mm f/4 without correction.
On the camera you can't disable distortion autocorrection. Thus normally you won't see those corners (5+EV vignetting there).
Your findings are not isolated, Fred Miranda has reported that too.
Does the resolution fall below the basement too?
I was about to ask if that's with distortion correction turned off.
I think it's a compromise. The question is, how looks the end results.
No strange, I have seen 6.33eV result at somewhere.
And what about the resolution?
I think it looks a lot like the old Sigma 10-20/4-5.6 at 11mm when mounted on a Canon 1D body (I've tried it a couple of times for fun when travelling in Kazakhstan). On the other hand, some people like to add this kind of trashy vignette in post anyway... (yeah... I'm trying to find a bright spot - pardon the pun
![Smile Smile](https://forum.opticallimits.com/images/smilies/smile.png)
)