I'm after a auto focus wide angle lens for my 6D that is very sharp and produces little distortion. I'm struggling to find much info from lens reviews when shooting at higher apertures. I am likely to be shooting at around 5.6-f8+ as I will need full focus of the scene, at approx 4m. 24mm would be ideal, however if a 35mm is significantly sharper and distortion is not truly correctable with 24mm I can go 35mm. CA is not acceptable. I have been looking at both the 24mm and 35mm Sigma Art Lens's. However understandably most reviews concentrate on wide open and bokeh, I am after the opposite. I can find little acurate info on how they perform with when trying to take a fully focused shot. I am aware most fast lens's perform optimally at around f4-5.6 however detailed comparisons at these settings I am struggling to find. I have a feeling that maybe a slower lens will perform just as well or even better. However it seems slower lenses appear to be of a lesser quality, I am sure there are exceptions to that, I would like to be aware of them. Any advice appreciated.