I started UWP just few years ago with compact camera Oly XZ-1. With small strobes and Inon lens I can do images sharp in corners at f around 4. Then the same lens I attached to Sony RX-100. To obtain similar sharpness and constant Iso=100 I have to close aperture up to f 6 or 8. Now I started to think about changing for DSLR. In tests of lenses I see that wide lens has to be closed to f 14 or 16 .
If I want to get sharp images in the corners, what is the advantage of bigger CCD like FullFrame ??
When I am looking for new lens I always check the resolution and sharpness diagrams and lenses like Tokina 10-17 dosent looks so great.
Even if the question sounds stupid or basic, please be patient to give answer. I am really in doubt.