Quote:any you have to remember that "full frame" is really only a crop of a phase one sensor...See my post above, concerning your 1st point.
Another thing to remember is that full frame lenses are usually pretty rubbish wide open towards the edges.
On the 2nd point:
It would be more correct to write: "Another thing to remember is that large aperture lenses usually are pretty rubbish, wide open towards the edges".
Which is often true. And which is pretty meaningless in a comparison debate, as the smaller sensored systems do not offer similarly big apertures.
Again the Canon to put things into perspective: Is the Canon 24mm f2.8 rubbish towards the edges?
Not according to PZ:
Will a bigger aperture lens at that big aperture (like lets say a Sigma 24mm f1.4 Art) be less sharp at the extremes than the smaller aperture lens at that smaller aperture (like for instance this "Leica" 12mm f1.4)? Yeah probably.
Does it make sense to make that comparison? Probably not.
It is the same as me putting my Nikkor-Sâ€¢C 55mm f1.2 lens on my camera and making an image at f1.2, then complaining it can actually give me that 45mm aperture because it is not as sharp as my Nikkor-Sâ€¢C 55mm f1.2 lens on my camera set at f5.6.
JoJu makes a good point in above post as well: with large apertures, edge performance most of the time does not matter (at least not with non-(super) telephoto lenses).
Anyway... back on topic:
Sharpness test "Leica" 12mm f1.4:
And how it renders (pretty nicely I think):